bluuebunny/crossref_metadata_2025 huggingface dataset:
Labor Migration between Developing Countries: The Case of Paraguay and Argentina
Authors: Parrado Emilio A. , Cerrutti Marcela
Published: August 2010

Despite the historical and numerical importance of international migration between Paraguay and Argentina, the socioeconomic forces affecting the dynamics of the flow remain largely unexplored. This article contributes to the understanding of migration movements between the Latin American countries by analyzing patterns of labor migration from two Paraguayan communities to Argentina. The analysis separates the process of migration into four segments representing different migration decisions that Paraguayan men face throughout their life course: first trip, first return, recurrent trips, and duration of additional trips. Results confirm that Paraguayan migration to Argentina is closely related to individual characteristics and wealth, the extent of migrant networks and experience, and changes in macroeconomic conditions. The relative importance of these factors on migration varies depending on the aspect of migration under consideration. More generally, the analysis shows that unlike migration between Mexico and the United States, Paraguayan migrants to Argentina tend to be positively selected with respect to educational attainment and skills. This reflects the higher transferability of skills between the two countries and the absence of large urban centers attracting internal migrants in Paraguay. In addition, results show that migration between Paraguay and Argentina is very responsive to fluctuations in macroeconomic conditions, particularly income differentials and peso over-valuation. Government policies oriented towards the regulation of migration flows in the Southern Cone should pay closer attention to the impact of macroeconomic fluctuations on migration decisions, especially in the context of the Mercosur agreement.
Diasporic Memberships in Historical Perspective: Comparative Insights from the Mexican, Italian and Polish Cases
Authors: Smith Robert C.
Published: August 2010

This article compares the evolution of diaspora-sending state relations for Mexico, Italy, and more briefly, Poland during their peak periods of out migration. I argue that sending-state diaspora relations evolve through the state's changing relations with the global system, their domestic politics, and migrants’ ability to act politically with respect to the homeland. This research shows the state helping to create diasporic or transnational space. It also contributes to the analytical work of fleshing out examples of transnational life in history, and examines a case (the Polish one) where the global system and other conditions combine to overwhelm transnational life.
The Second Generation in Germany: Between School and Labor Market
Authors: Worbs Susanne
Published: August 2010

The German “mode of integration” after World War II has been to include migrants and their offspring into general societal institutions. This can be stated despite differences between federal states in some aspects of migrant integration {e.g., the educational sector). Migrant children normally attend the same schools and classes as their German age peers, they participate in the dual system of vocational training, and there are only a few limitations in labor market access. The second generation in Germany consists mainly of children of the “guestworkers” recruited in southern and southeastern European countries from the 1950s onwards. It is not easy to obtain information about their numbers and their socioeconomic position, as most statistical data distinguish only between foreigners and Germans. The achieved integration status of the second generation varies between areas: obvious problems in the educational system go along with considerable progress in the vocational training system and in the labor market. Children of Turkish migrants are the most disadvantaged group among the second generation.
Occupational Destinations and Economic Mobility of Filipino Overseas Workers
Authors: Semyonov Moshe , Gorodzeisky Anastasia
Published: August 2010

This study examines employment and occupational shifts experienced by Filipino overseas contract workers in the transition from country of origin to country of destination and examines the impact of labor migration on economic conditions and standard of living of the families left behind. Data for the analyses were obtained from a representative sample of 2,346 households drawn from four primary sending areas in the Philippines. The analyses focus on characteristics of the households and of the household members employed overseas. The findings reveal that a considerable number of overseas workers (both men and women) were unemployed prior to migration and that the overwhelming majority of these workers were recruited to fill low-status (manual and service) occupations in the host country. The analysis demonstrates that the odds for Filipino overseas workers to be employed in low-status occupations were extremely high, net of human capital characteristics, net of the occupations they held in the Philippines, and net of country of destination. Further analysis reveals that overseas employment is associated with a substantial increase in earnings (five-fold for men and four-fold for women). Comparison between households with and without overseas workers reveals that, net of household characteristics, the flows of income earned abroad are used to purchase household goods to improve standard of living. These findings provide firm support to expectations derived from the household theory of migration according to which labor migration is a strategy adopted by the household unit to allocate family resources rationally to increase the flows of income in order to raise the family standard of living.
“Tel Aviv is Not Foreign to You”: Urban Incorporation Policy on Labor Migrants in Israel
Authors: Kemp Adriana , Raijman Rebeca
Published: August 2010

This article addresses the growing disjuncture between urban and national policies regarding the incorporation of labor migrants in Israel. Drawing on fieldwork, in-depth interviews with Tel Aviv municipal officials, and archive analysis of Tel Aviv municipality minutes, we argue that urban migrant-directed policy elicits new understandings of membership and participation, other than those envisaged by national parameters, which bear important, even if unintended, consequences for the de facto incorporation of non-Jewish labor migrants. The crux of the Tel Aviv case is that its migrant-directed policy bears especially on undocumented labor migrants, who make up approximately 16 percent of the city's population and who are the most problematic category of resident from the state's point of view. In demanding recognition for the rights of migrant workers in the name of a territorial category of “residence,” and by activating channels of participation for migrant communities, local authorities in Tel Aviv are introducing definitions of “urban membership” for noncitizens which conflict sharply with the hegemonic ethnonational policy. We suggest that the disjuncture between urban and national incorporation policies on labor migrants in Israel is part of a general process of political realignment between the urban and the national taking place within a globalized context of labor migration.
Temporary Migration and the Spread of STDs/HIV in China: Is There a Link?
Authors: Yang Xiushi
Published: August 2010

Using data from the literature and a specially designed community-level survey, this article examines the link between temporary migration and the spread of HIV/STDs in China. The results suggest that temporary migrants not only are overrepresented among people with STD/HIV risk-taking behaviors, but also account for disproportionately more STD patients and persons infected with HIV. It is imperative that STD and AIDS prevention intervention and education programs in China target temporary migrants. More research is needed that focuses on the underlying mechanisms by which the process of temporary migration renders migrants vulnerable to STD/HIV risk-taking behaviors.
Parental Influences on the Educational Outcomes of Immigrant Youth
Authors: Kao Grace
Published: August 2010

Recent research suggests that children with immigrant parents tend to outperform their counterparts with native-born parents. This article examines whether the relative advantage of children of immigrants can be traced to differences in the character of parent-child relationships. Using the National Education Longitudinal Study of 1988 (NELS), I examine whether parent-child interaction varies among racial and generational groups. Descriptive tabulations suggest that immigrant parents are less likely to share decisionmaking power and to talk about school in general than are native-born parents. However, immigrant parents are more likely to talk about college, and their children report that they are closer to their parents than youth of native-born parents. While differences in parent-child interaction account for some of the differences in educational achievement between racial and generational groups, significant variation by race and generational status remains. Finally, I found significant variation between parenting behavior and its impact on GPA by race and ethnicity.
The Origins of Popular Opposition to Palestinian Resettlement in Lebanon
Authors: Haddad Simon
Published: August 2010

Using original public opinion data, this study addresses the reasons behind the growing popular opposition to Palestinian resettlement in Lebanon. It argues that the origins of this opposition are correlated to the religious composition of the population and to the degree of social distance displayed by the Lebanese towards the Palestinians as members of a distinct community. The results revealed that Lebanese respondents are much less likely to support Palestinian resettlement in Lebanon if they display prejudice and hostility toward Palestinians. In addition, sectarian affiliation is a major predictor of attitude toward resettlement. Specifically, Christian and Shii respondents expressed unfavorable views toward resettlement, in contrast to Sunni and Druze respondents who manifested positive support for resettlement. Hence, for most Lebanese the question of Palestinian resettlement extends to their own political survival. If the existing attitudes hold, resettlement threatens to undermine Lebanon's pluralist character and consensus political arrangement, with implications for the entire region.
Wealth of Immigrant and Native-Born Americans
Authors: Hao Lingxin
Published: August 2010

This study hypothesizes nativity differences in the process of wealth accumulation with regards to accumulation rates, dissaving rates, the role of human capital, saving intention for children, and structural barriers to wealth accumulation. Based on an analysis of the 1992 and 1993 panels of the Survey of Income and Program Participation (SIPP), it reports four major findings. First, levels of net worth, life cycle patterns, and wealth components are primarily stratified by national origin and race-ethnicity rather than by nativity. Second, when immigrants’ adult years in the United States are taken into account, the life cycle pattern of wealth of the post-1965 immigrants catches up with that of natives within 22 years of arrival and then overtakes natives. Third, the process of wealth accumulation is similar for immigrants and natives in all but two respects – for immigrants, education is discounted and adult years in the United States matter. Lastly, spatial segregation has a uniform negative effect on wealth for both immigrants and natives.
Childbearing after Migration: Fertility Patterns of Foreign-born Women in Sweden
Authors: Andersson Gunnar
Published: August 2010

The present study provides an investigation of patterns in childbearing among foreign-born women in Sweden from the 1960s to the 1990s. Event-history techniques are applied to longitudinal population register data on childbearing and migration of 446,000 foreign-born women who had ever lived in Sweden before the end of 1999. Period trends in parity-specific fertility appear to be quite similar for Swedish- and foreign-born women, but important differences exist in levels of childbearing propensities between women from different countries of origin. Most immigrant groups tend to display higher levels of childbearing shortly after immigration. We conclude that migration and family building in many cases are interrelated processes and that it is always important to account for time since migration when fertility of immigrants is studied.
Migrant Transnationalism and Modes of Transformation
Authors: Vertovec Steven
Published: August 2010

Much of the literature on migrant transnationalism focuses on the ways that specific sociocultural institutions have been modified in the course of being stretched across the globe. Yet migrant transnational practices are involved in more deep-seated patterns of change or structural transformation. Such modes of transformation concern: 1) an enhanced ‘bifocality’ of outlooks underpinning migrant lives lived here-and-there; such dual orientations have considerable influence on transnational family life and may continue to affect identities among subsequent post-migration generations; 2) heightened challenges to ‘identities-borders-orders’ stemming from migrants’ political affiliations in more than one nation-state; these particularly arise around questions of dual citizenship and nationality; and 3) potentially profound impacts on economic development by way of the sheer scale and evolving means of remittance sending; money transfer services, hometown associations and micro-finance institutions represent three kinds of remittance-related organizations currently undergoing significant forms of adaptation with significant consequences for development. These modes of transformation, and the practices of migrant transnationalism surrounding them, both draw from and contribute to wider processes of globalization.
Illegal Migration: What can We Know and what can we Explain? The Case of Germany
Authors: Heckmann Friedrich
Published: August 2010

Methodological problems in the study of illegal migration as defined in this article relate to questions of indicators for illegal migration, with special reference to Germany. It is argued and demonstrated that illegal immigrants are traceable, to some degree, in official statistics and that these can be analyzed for trends. In present-day migration processes, illegal immigration frequently is undertaken with the support of human smugglers. The analysis of the social organization of different forms of smuggling is the other main focus of the article. From a methodological point of view, the literature and public discourse lack adequate concepts for describing and explaining the social organization of human smuggling. The theory of organized crime as a main actor in human smuggling is criticized. The study borrows concepts from market and networks theory and applies these to different forms of human smuggling and illegal migration. The social and technological organization of smuggling is under constant pressure to adapt to new conditions. The dynamism for this change results mainly from an “arms race” between smugglers and law enforcement. Since control over territory and population are central elements of state sovereignty, the state cannot simply withdraw from this race.
How Do Migrants Fare in a Post-Apartheid South African Labor Market?
Authors: Zuberi Tukufu , Sibanda Amson
Published: August 2010

South African policies have historically emphasized employment as the reason for immigration. In post-apartheid South Africa, stories about how “immigrants take away our jobs” abound in the mass media, yet few empirical studies have been undertaken to examine the validity of this claim. This study looks at the relationship between migration status, nativity and labor force outcomes in the post-apartheid labor market. Our results suggest that migrants are more likely to participate in the labor force and to be gainfully employed than the indigenous population. Foreign migrants enjoy the highest labor force participation rates and employment rates in South Africa. South African-born internal migrants also have significantly higher labor force outcomes than do nonmigrants.
EDGE PERMEABILITY AND POPULATION PERSISTENCE IN ISOLATED HABITAT PATCHES
Authors: KIRK R.W. VAN , LEWIS M.A.
Published: August 2010

ABSTRACT. Population persistence in isolated habitat fragments is investigated using integrodifference equations. The propensity of individual dispersers encountering the boundary of the patch to emigrate is defined by edge permeability. A dispersal model incorporating movement, settlement and edge permeability defines dispersal success as a function of a disperser's starting location. This dispersal model is used to generate dispersal kernels for integrodifference equation models, analysis of which gives a condition for population persistence in terms of edge permeability, patch size and average dispersal distance. An approximation reduces the spatial problem to a simple nonspatial model that can be easily analyzed.
A METAPHYSIOLOGICAL POPULATION MODEL OF STORAGE IN VARIABLE ENVIRONMENTS
Authors: GETZ WAYNE M. , OWEN‐SMITH NORMAN
Published: August 2010

ABSTRACT. We use mechanistic arguments to generalize a hierarchical metaphysiological approach developed by one of us to modeling biological populations (Getz, [1991, 1993]) and extend the approach to include a storage component in the population. We model the growth of single species and consumer‐resource interactions, both with and without storage. Our approach unifies modeling storage across trophic levels and is much simpler and more efficient to implement numerically than individual based approaches or population approaches that include integral, delay, or partial differential equation components in the model. Using intake functions (i.e., functional responses) that include the effects of interference competition, we apply the model to a hypothetical herbivore feeding on a resource that fluctuates seasonally and demonstrate the importance of a flow from storage that buffers the population against periods when resources are scarce or absent. We also apply the model to a hypothetical plant population that is driven by fluctuating resources and demonstrate the importance of a translocation flow from storage at the end of a dormant season, corresponding to periods when resources are most scarce. Finally, we couple these two populations for the case where the herbivore feeds exclusively on non‐storage biomass, and demonstrate how the population dynamics can be affected by the rates at which buffering and translocation flows transfer from storage to active tissue in the herbivore and plant populations. In particular, for certain buffering and translocation flow rates, 1‐year unimodal, 2‐year bimodal, and 2‐year unimodal cycles can emerge in the same herbivore population.
THE COSTATE VARIABLE IN NATURAL RESOURCE OPTIMAL CONTROL PROBLEMS
Authors: LYON KENNETH S.
Published: August 2010

ABSTRACT. In this paper we discuss the role of the costate variable (shadow value) for the resource stock in both nonrenewable and renewable resource problems. We separate the information in this variable into a scarcity and a cost effect. The scarcity effect is the portion of the shadow value that is due just to the scarcity of the resource relative to its demand, while the cost effect is a measure of the impact of the marginal unit upon future extraction costs. It is shown that in the nonrenewable resource, mining, problem both can exist simultaneously, but in the renewable resource, fisheries, model the two effects are mutually exclusive. In our analysis of the fisheries model we develop an expression for the time path of the marginal unit of fish stock. We do this using the theorem of Continuous Dependence on Initial Conditions. This result is then used to generate the conclusion that g(x) is the biological own rate of interest, where g(x) is the growth function for the resource stock, x.
DIFFUSION AND BIFURCATION PROBLEMS IN SINGULARLY PERTURBED DOMAINS
Authors: WARD MICHAEL J.
Published: August 2010

ABSTRACT. Diffusion problems under singular perturbations of the domain or the boundary conditions are analyzed. The first problem that we consider is the diffusion of a material from a domain that is nearly impermeable, having only several small patches on the boundary where the material can slowly leak out. The second problem that is studied is the diffusion of a material that originates from some localized regions in a two or three‐dimensional domain. Steady‐state solutions and the long‐time behavior of solutions are analyzed in detail. Finally, the analysis is extended to determine the change in bifurcation values associated with nonlinear diffusion equations under singular perturbations of the domain. The results are then applied to a model in resource management.
COMPUTATION OF THE RELAXATION OSCILLATION PERIOD IN LOTKA‐VOLTERRA SYSTEMS
Authors: SHIH SHAGI‐DI , MATHEW TAREK P.
Published: August 2010

ABSTRACT. This work surveys techniques of Grasman and Veling [1973], Vasil'eva and Belyanin [1988] and Shih [1996] for computing the relaxation oscillation period of singularly perturbed Lotka‐Volterra systems. Grasman and Veling [1973] used an implicit function theorem to derive an asymptotic formula for the period; Vasil'eva and Belyanin [1988] employed a method of matched asymptotic expansions to obtain an approximation to the period; Shih [1996] obtained two (exact) integral representations for the period in terms of two inverse functions W(–k, x) of xexp(x). These results are compared numerically and asymptotically. In particular, the integral representation of the period in Shih [1996] is computed numerically using a Gauss‐Tschebyscheff integration rule of the first kind, and is further investigated asymptotically by virtue of the asymptotics of W(–k, x), Laplace's method, and a method of consequent representation. Computational results indicate that the Gauss‐Tschebyscheff approximation of the period in Shih [1996] is uniformly accurate for a wide range of the singular parameter (ɛ in the paper).
THE LONG‐RUN INEFFICIENCY OF BLOCK‐RATE PRICING
Authors: BAR‐SHIRA ZIV , FINKELSHTAIN ISRAEL
Published: August 2010

ABSTRACT. In this paper we compare two regulation instruments, flat‐rate and increasing block‐rate pricing. The analysis applies to a competitive industry with free entry. Charge for irrigation water is a concrete example. It is shown that flat‐rate pricing leads to a first‐best social optimum, while with block‐rate pricing where the highest block set at the marginal cost, there is over production, firms are too small, and loss of economic surplus occurs. Moreover, first‐best is not implementable by increasing block‐rate pricing. This is in contrast to the commonly accepted view that block‐rate pricing is superior to flat‐rate pricing by allowing for income redistribution while preserving efficiency. Several second‐best situations are analyzed to show: 1) Block‐rate pricing with the highest block at the social marginal cost is optimal when the regulator must preserve the number of firms. 2) Water pricing alone cannot implement social optimum subject to a constant level of agricultural production. 3) Lobbying and political pressures, which force the regulator to sustain a constant average water price, result in optimal block‐rate pricing with the highest block below the social marginal cost.
STRUCTURED MODELS OF PATTERN FORMATION OF TREE POPULATIONS
Authors: KAREV GEORGY P.
Published: August 2010

ABSTRACT. The problem of mathematical modeling of the phenomenon of appearance and forming of allocated tree subpopulations, called gap, locus, cenon is studied. Such a subpopulation (not a single tree) is considered as an individual object of the forest community. A mathematical model describing the phenomenon of cenon formation as a result of natural dynamics of initial heterogeneous tree subpopulation is suggested. The model is constructed in the framework of a structural population model of one generation with distributed values of parameters and initial states. The “biological basis” of cenon formation is the so‐called discriminating death. It is shown that this component of death accounted for the model results in the formation of the comparatively homogeneous subpopulation from the initial heterogeneous sub‐population of trees.
FEATURES OF BIOECONOMICS MODELS FOR THE OPTIMAL MANAGEMENT OF A FISHERY EXPLOITED BY TWO DIFFERENT FLEETS
Authors: RAÏSSI N.
Published: August 2010

ABSTRACT. After the extension of the Exclusive Economic Zone, in 1977, to 200 miles, most fish stocks came under jurisdiction of the adjacent coastal states. This development opened prospects of effective management of the open sea fisheries. Coastal states have the right to plan out the operation of so‐called by Clarke and Munro “distant water fishing nations” from their Exclusive Economic Zone. Under some arrangements, a foreign fleet is allowed to harvest the resource in the Exclusive Economic Zone area. Clarke and Munro, in [1987] and [1991], focus on the issue of optimum terms and conditions of access and, in doing so, built a multiobjective model. The main goal of the present work is the development of a more general model including more variables and parameters related to the presence of a domestic fleet as well as a distant water fishing nation. The main difficulty resides in sharing the harvesting between the two fleets. The study responds to the realistic problemof coastal states who own enough resource stocks to allow harvesting by several kinds of fleets. Two optimal scenarios are developed, in each of them a solution is given.
FEATURES AND APPLICATIONS OF BERTALANFFY‐RICHARDS‘ AND SCHNUTE'S GROWTH EQUATIONS
Authors: YUANCAI LEI , MARQUES CARLOS PACHECO , BENTO JOÃO MANUEL
Published: August 2010

ABSTRACT. Based on various ranges of the parameter m (or b), the paper analyzes the features and the integral forms of the Schnute and the Bertalanffy‐Richards growth equations as well as the two aspects of their special cases (such as Gompertz, logistic and monomolecular models). It is a first attempt to investigate all the corresponding relationships among parameters of the models derived from the Schnute and the Bertalanffy‐Richards growth equations. All the models from the two are empirically fitted by different data sets for eucalypt plantations. Unlike earlier papers, the results of this paper show that either of the two growth equations can be considered as a model for estimating forest growth given a parameter range, and both can produce similar growth performances. Some other aspects of the two growth equations are discussed so that the two can be used correctly.
A GLOBAL MODEL OF POPULATION‐RESOURCE INTERACTION
Authors: BADGER LEE
Published: August 2010

ABSTRACT. A global model of population‐resource interaction is proposed consisting of two first order ordinary differential equations. In it the population growth rate increases due to increasing technology, then declines due to declining resources. When the model is fit to twentieth century data it predicts that global population will peak and then decline while already declining global resources bottom out; both will eventually stabilize slightly above their lows. Because of the uncertainty of model parameters and resource data, the values and times of these peaks and lows are uncertain, but the qualitative behavior of the model transcends this uncertainty. Actual best‐fit values of population include a peak of nearly nine billion about year 2050 and a peak rate of decline of 0.3% about year 2100. Global resources bottom out at 70% of optimum around year 2100. Variability and sensitivity analyses are also provided.
THE POSSIBILITY OF CONTINUOUS GROWTH WITH EXHAUSTIBLE RESOURCES: UNKNOWINGLY AN AGREEMENT HAS BEEN REACHED, BUT IT MAY NOT BE CORRECT
Authors: PETITH HOWARD
Published: August 2010

ABSTRACT. It is the size of the elasticity of substitution that has been the central issue in the long debate over the possibility of continuous growth in the presence of exhaustible resources. This paper reviews the debate and comes to the surprising conclusion that, unnoticed by pessimists, the optimist position has gradually evolved so that it now approximates that of the pessimists. The paper also summarizes some preliminary work by the author that indicates that this common position may not be correct.
FORECASTING TREE SIZE DISTRIBUTION BY NUMERICAL APPROXIMATION OF THE FORWARD KOLMOGOROV EQUATION
Authors: WICHMANN LARS
Published: August 2010

ABSTRACT. Forest management planning of uneven‐aged stands involves forecasting of the tree size distribution. The temporal development of the size distribution in a forest stand may be described by the forward Kolmogorov equation. The objective of this study is to illustrate that numerical approximation of the solution to the equation provides a reasonably accurate way of forecasting future tree size distribution, especially for stands with non‐normal size distribution. Furthermore, a method for the practical application is devised. The analyses compare observed and forecasted tree size distributions for two forest stands, 1) an unthinned stand of Sitka spruce (Picea sitchensis (Bong.) Carr.), and 2) an uneven‐aged stand of beech (Fagus sylvatica L.) managed under the selection system. The analyses show that the size distribution in the uneven‐aged stand may be forecasted correctly for a 20 25 year period, while for the even‐aged stand the method seems to fail after 10 to 15 years.
GOLDEN AGES OR MAGIC MOMENTS?
Authors: POPE JOHN
Published: August 2010

ABSTRACT.The paper is an attempt to refute Quinn's ‘the Golden Age of fisheries population models has ended “hypothesis. The approach is to show it is possible to provide simple matrix based theory for use with delay difference equations applied to products of the 0th to 4th powers of length and numbers at length (Alias” proto‐moments“). It compares these to models just based upon numbers and biomass. It also shows examples (of comparatively little moment) indicating how using multiple proto‐moments could improve the ability of delay difference equations to handle the size dependent processes of maturity, selection, natural mortality rates and predation rates and thus improving the biological reality of these models.
MODELING THE DYNAMICS OF FISHERY STOCK RECOVERY: IMPLICATIONS FOR THE ASSESSMENT OF NATURAL RESOURCE DAMAGES
Authors: SCHUHMANN PETER W. , SCHWABE KURT A.
Published: August 2010

ABSTRACT. During the restoration planning phase of the natural resource damage assessment (NRDA) process, potential injuries to natural resources and services are evaluated in terms of the nature, degree and extent of injury so that the need for and scale of restoration actions can be ascertained. Injuries are quantified by comparing the condition of the injured natural resource relative to baseline (pre‐injury) conditions. The “Type A” procedures are used to quantify damages from smaller spills and rely on a standardized methodology and computer model to calculate injury and value of damages. In this model, fishery stock changes from injuries and resulting changes in user participation are not treated as dynamic. If true stock growth and re‐growth are indeed dynamic, then the Type A model is likely underestimating fishery losses. The purpose of this paper is to illustrate the potential for such underestimation by comparing simulated stock and harvest losses under dynamic treatment and a static treatment that more closely represents the way stock and service losses are estimated under the current NRDA process.
MODELS FOR THE EFFECT OF HIGH SPEED WIND ON THE DEPLETION OF FERTILE TOPSOIL
Authors: DUBEY B.
Published: August 2010

ABSTRACT. In this paper a mathematical model is proposed and analyzed to study the effect of high speed wind on the depletion of fertile topsoil depth and crop yield. The system is modeled by considering a Cobb‐Douglas production function which depends on depreciating capital stock, a labor force and depth of fertile topsoil. A model to conserve the depth of fertile topsoil and to control the high speed wind is also presented.
FISHING YIELD, CURVATURE AND SPATIAL BEHAVIOR: IMPLICATIONS FOR MODELING MARINE RESERVES
Authors: SMITH MARTIN D.
Published: August 2010

ABSTRACT. Given a paucity of empirical data, policymakers are forced to rely on modeling to assess potential impacts of creating marine reserves to manage fisheries. Many modeling studies of reserves conclude that fishing yield will increase (or decrease only modestly) after creating a reserve in a heavily exploited fishery. However, much of the marine reserves modeling ignores the spatial heterogeneity of fishing behavior. Contrary to empirical findings in fisheries science and economics, most models assume explicitly or implicitly that fishing effort is distributed uniformly over space. This paper demonstrates that by ignoring this heterogeneity, yield‐per‐recruit models systematically overstate the yield gains (or understate the losses) from creating a reserve in a heavily exploited fishery. Conversely, at very low levels of exploitation, models that ignore heterogeneous fishing effort overstate the fishing yield losses from creating a reserve. Starting with a standard yield‐per‐recruit model, the paper derives a yield surface that maps spatially differentiated fishing effort into total long‐run fishing yield. It is the curvature of this surface that accounts for why the spatial distribution of fishing effort so greatly affects predicted changes from forming a reserve. The results apply generally to any model in which the long‐run fishing yield has similar curvature to a two‐patch Beverton‐Holt model. A simulation of marine reserve formation in the California red sea urchin fishery with Beverton‐Holt recruitment, eleven patches, and common larval pool dispersal dynamics reinforces these results.
FIRE OCCURRENCE PATTERNS AT LANDSCAPE LEVEL: BEYOND POSITIONAL ACCURACY OF IGNITION POINTS WITH KERNEL DENSITY ESTIMATION METHODS
Authors: KOUTSIAS NIKOS , KALABOKIDIS KOSTAS D. , ALLGÖWER BRITTA
Published: August 2010

ABSTRACT. Based on kernel density estimation methods, this paper introduces an alternative approach of fire occurrence modeling that addresses the inherent positional inaccuracies of recorded wildland fire ignition points. These observations, recorded in longitude and latitude using only degrees and first minutes, contain positional inaccuracies of about ± 700 to ± 925 meters in x and y axes. Kernel density estimation was applied to these historical fire observations recorded between 1985 and 1995 in Halkidiki peninsula, Greece, as well as, to simulated inaccurate points into which positional inaccuracies of the same magnitude were randomly introduced. Substantial differences were observed when a regular grid of quadrants was superimposed over the two point distributions. Although, at higher grid resolution these mismatches were minimized, the problem of generalization appeared. Contrar‐ily, the concept of “moving window” assisted to retain high grid resolution and minimize the effect of inaccurate point observations. In addition, the kernel approach, which considers also the relative position of points within the “moving window,” produced more realistic estimates.
DYNAMICS OF AN AGE‐STRUCTURED METAPOPULATION MODEL
Authors: FENG ZHILAN , RONG LIBIN , SWIHART ROBERT K.
Published: August 2010

ABSTRACT. We introduce a metapopulation model that includes both landscape changes (patch destruction and recreation) and age‐dependent metapopulation dynamics. A threshold quantity is derived and related to the existence of an ecologically nontrivial equilibrium, to the stability of the species‐free equilibrium, and to weak and strong persistence of the species. We provide examples to illustrate how age‐related changes in patch colonization and extinction rates can alter metapopulation persistence. Future field studies may need to address the temporal dynamics that characterize local populations in fragmented landscapes.
HABITAT PATCH OCCUPANCY DYNAMICS OF GLAUCOUS‐WINGED GULLS (LARUS GLAUCESCENS) II: A CONTINUOUS‐TIME MODEL
Authors: DAMANIA SMRUTI P. , PHILLIPS KARL W. , HENSON SHANDELLE M. , HAYWARD JAMES L.
Published: August 2010

ABSTRACT. The diurnal distribution and abundance dynamics of loafing Glaucous‐winged Gulls (Larus glaucescens) were examined at Protection Island National Wildlife Refuge, Strait of Juan de Fuca, Washington. Asynchronous movement of gulls among three habitat patches dedicated to loafing was modeled as a function of environmental variables using differential equations. Multiple time scale analysis led to the derivation of algebraic models for habitat patch occupancy dynamics. The models were parameterized with hourly census data collected from each habitat patch, and the resulting model predictions were compared with observed census data. A four‐compartment model explained 41% of the variability in the data. Models that predict the dynamics of organism distribution and abundance enhance understanding of the temporal and spatial organization of ecological systems, as well as the decision‐making process in natural resource management.
AN AXIOMATIC APPROACH TO SUSTAINABILITY
Authors: HELLWIG KLAUS
Published: August 2010

ABSTRACT. In this paper a new concept for sustainable development is proposed. Unlike the usual present value maximizing approach, the discount rates are determined endoge‐nously. For a standard model of renewable natural resources it is shown that a solution can be found by solving an appropriate system of equations.
ECOLOGICAL‐ECONOMIC MODELS OF SUSTAINABLE HARVEST FOR AN ENDANGERED BUT EXOTIC MEGAHERBIVORE IN NORTHERN AUSTRALIA
Authors: BRADSHAW COREY J.A. , BROOK BARRY W.
Published: August 2010

ABSTRACT. How can one manage wildlife under a suite of competing values? In isolation, the ecological economics of native wildlife harvest, threatened species conservation and control of exotic species are all well established sub‐disciplines of wildlife management. However, the wild banteng (Bos javanicus) population of northern Australia represents an interesting combination of these aspirations. A native bovid of Southeast Asia now ‘endangered’ in its native range, banteng were introduced into northern Australia in 1849. Today, a population of 8,000–10,000 resides on one small, isolated peninsula in western Arnhem Land, Northern Territory and is harvested by both recreational (trophy) and aboriginal subsistence hunters. Indigenous, industry and conservationist stakeholders differ in their requirements for population management. Here we analyze the ecological and economic costs/benefits of a series of potential harvest management options for Australia's banteng population, with the aim being either to: (1) maximize sustainable yield (MSY); (2) maximize harvest of trophy males; (3) maximize indigenous off‐take; (4) suppress density or completely eradicate the population; (5) minimize risk of extinction whilst limiting range expansion; (6) scenarios incorporating two or more of options 1–5. The modeling framework employed stochastic, density‐regulated matrix population models with life‐history parameters derived from (i) allometric relationships (for estimating rmax, generation length, fecundity and densities for a banteng‐sized mammal) and (ii) measured vital rates for wild and captive banteng and other Bos spp. For each management option, we present a simple economic analysis that incorporates estimated costs of management implementation and associated profits projected. Results demonstrate that revenue of >Ä$200,000 is possible from meat production and safari hunting without compromising long‐term population stability or the conservation status of this endangered bovid.
ECONOMIC IMPACTS OF GLOBAL WARMING: THE CASE OF THE BARENTS SEA FISHERIES
Authors: EIDE ARNE
Published: August 2010

ABSTRACT. . Regional analyses of possible physical and biological effects of global warming in the Barents Sea area have been carried out recently. Based on such studies possible economic impacts of global warming on the Barents Sea fisheries have been quantified, assuming different types of management regimes. The EconSimp2000 model, consisting of the ecosystem model AggMult and the fleet model EconMult have been parameterized based on fleet and catch records from the Norwegian Barents Sea fisheries. The model has been used to study biological and economic impacts of different environmental scenarios representing possible consequences of global warming. The current environmental situation, including normal seasonal and other variations, has been used as a reference scenario. Several biological and economic indicators have been defined in order to evaluate the simulation results of different environmental scenarios and different types of management regimes. The findings support earlier studies where biological and economic impacts of changes in management regime is found to be more pronounced than impacts caused by effects of global warming.
ROYALTY INCENTIVES AND GULF OF MEXICO OIL PRODUCTION
Authors: KUNCE MITCH
Published: August 2010

ABSTRACT. This paper employs field‐specific estimates of Pindyck's (1978) widely cited model of natural resource supply to simulate effects of changes in federal royalty rates on the timing of exploration and output by firms in the deepwater Gulf of Mexico oil industry. Results suggest that deepwater Gulf oil production is highly inelastic with respect to changes in royalty rates. Royalty rate decreases are shown to increase early period exploration effort, result in little change in reserve additions and future production. Policy implications of this study suggest that public officials should be wary of arguments that large increases in deepwater Gulf oil field activity can be obtained from reductions in federal royalty rates‐particularly reductions in the early years of oil field development.
STEADY STATE AND INTERTEMPORAL MANAGEMENT MODELS FOR MARINE FISHERIES
Authors: HASHIM N.M. NIK
Published: August 2010

Abstract Steady state and dynamic management models are developed for analyzing the Malaysian marine fisheries. These models originate from the theoretical concepts of the natural resource economics namely the open access, limited entry and the intertemporal fishery models. Such management models are deemed necessary because of the need to sustain the depleting resource and degrading environment. Marine fisheries had been managed under open access for a long time before government intervention took effect sometime during the 1960s. Open access and government intervention during the earlier phase of economic development contributed to the immediate pressure on fisheries. Community development programs geared to alleviate poverty among the fishermen apparently contradicted the effort of sustaining fisheries. Even today this fundamental management objective of sustainable development of fishery resource is not fully adhered to. This study suggests that ability to sustain fishery requires government intervention that can direct resource use to steady state or intertemporal optimal levels.
A REACTION–DIFFUSION EQUATION MODELING THE INVASION OF THE ARGENTINE ANT POPULATION, LINEPITHEMA HUMILE, AT JASPER RIDGE BIOLOGICAL PRESERVE
Authors: SHRYOCK KACEE A. , BROWN SHARON L. , SANDERS NATHAN J. , BURROUGHS ELIZABETH
Published: August 2010

Abstract A continuous reaction–diffusion model is developed for the invasive Argentine ant population within a preserve in northern California. The model is a second‐order partial differential equation incorporating a logistic growth term. The dispersal distance traveled during the reproductive process of budding is used to estimate the diffusion coefficient. The model has two homogeneous steady states, one occurring at the propagation front where the Argentine ant population does not yet exist and one occurring where the population has reached carrying capacity. The traveling wave solutions of the model depict the population density for a given time and location. Using current research, parameter values for the model are estimated and a traveling wave solution for the average parameter values is numerically demonstrated.
HARVESTING AN AGE‐STRUCTURED POPULATION AS BIOMASS: DOES IT WORK?
Authors: TAHVONEN OLLI
Published: August 2010

AbstractThe economics of fisheries is based heavily on describing fish populations by the surplus production model. Both economists and ecologists have different opinions on whether this approach provides an adequate biological basis for economic analysis. This study takes an age‐structured population model and shows how, under equilibrium conditions, it determines the surplus production model. The surplus production model is then used to solve an optimal feedback policy for a generic optimal harvesting problem. Next, it is assumed that the fishery manager applies this feedback policy even though the fish population actually evolves according to the age‐structured model. This framework is applied to the widow rockfish, Atlantic menhaden, and Pacific halibut fisheries. Population age‐structure contains information on future harvest possibilities. The surplus production model neglects this information and may lead to major deviations between the expected and actual outcomes especially under multiple steady states and nonlinearities.
Characterization of a Cellobiohydrolase (MoCel6A) Produced by
Magnaporthe oryzae
Authors: Takahashi Machiko , Takahashi Hideyuki , Nakano Yuki , Konishi Teruko , Terauchi Ryohei , Takeda Takumi
Published: August 2010

Three GH-6 family cellobiohydrolases are expected in the genome of
Magnaporthe grisea
based on the complete genome sequence. Here, we demonstrate the properties, kinetics, and substrate specificities of a
Magnaporthe oryzae
GH-6 family cellobiohydrolase (MoCel6A). In addition, the effect of cellobiose on MoCel6A activity was also investigated. MoCel6A contiguously fused to a histidine tag was overexpressed in
M. oryzae
and purified by affinity chromatography. MoCel6A showed higher hydrolytic activities on phosphoric acid-swollen cellulose (PSC), β-glucan, and cellooligosaccharide derivatives than on cellulose, of which the best substrates were cellooligosaccharides. A tandemly aligned cellulose binding domain (CBD) at the N terminus caused increased activity on cellulose and PSC, whereas deletion of the CBD (catalytic domain only) showed decreased activity on cellulose. MoCel6A hydrolysis of cellooligosaccharides and sulforhodamine-conjugated cellooligosaccharides was not inhibited by exogenously adding cellobiose up to 438 mM, which, rather, enhanced activity, whereas a GH-7 family cellobiohydrolase from
M. oryzae
(MoCel7A) was severely inhibited by more than 29 mM cellobiose. Furthermore, we assessed the effects of cellobiose on hydrolytic activities using MoCel6A and
Trichoderma reesei
cellobiohydrolase (TrCel6A), which were prepared in
Aspergillus oryzae
. MoCel6A showed increased hydrolysis of cellopentaose used as a substrate in the presence of 292 mM cellobiose at pH 4.5 and pH 6.0, and enhanced activity disappeared at pH 9.0. In contrast, TrCel6A exhibited slightly increased hydrolysis at pH 4.5, and hydrolysis was severely inhibited at pH 9.0. These results suggest that enhancement or inhibition of hydrolytic activities by cellobiose is dependent on the reaction mixture pH.
Mycobacterium avium
Infections of
Acanthamoeba
Strains: Host Strain Variability, Grazing-Acquired Infections, and Altered Dynamics of Inactivation with Monochloramine
Authors: Berry David , Horn Matthias , Xi Chuanwu , Raskin Lutgarde
Published: August 2010

Stable
Mycobacterium avium
infections of several
Acanthamoeba
strains were characterized by increased infection resistance of recent environmental isolates and reduced infectivity in the presence of other bacteria. Exposure of
M. avium
in coculture with
Acanthamoeba castellanii
to monochloramine yielded inactivation kinetics markedly similar to those observed for
A. castellanii
alone.