scholarly journals On mechanisms of trophic cascade caused by anti-predation response in food chain systems

2020 ◽  
Vol 1 (2) ◽  
pp. 1-27
Author(s):  
Yang Wang ◽  
Xingfu Zou
Keyword(s):  
Food Chain ◽  
Trophic Cascade ◽  
Predation Rate ◽  
Model Systems ◽  
Large Carnivores ◽  
Response Level ◽  
Population Sizes ◽  
The Cost ◽  
The Impact ◽  
D Model

Motivated by a recent field study [Nat. Commun. 7(2016), 10698] on the impact of fear of large carnivores on the populations in a cascading ecosystem of food chain type with the large carnivores as the top predator, in this paper we propose two model systems in the form of ordinary differential equations to mechanistically explore the cascade of such a fear effect. The models are of the Lotka-Volterra type, one is three imensional and the other four dimensional. The 3-D model only considers the cost of the anti-predation response reflected in the decrease of the production, while the 4-D model considers also the benefit of the response in reducing the predation rate, in addition to the cost by reducing the production. We perform a thorough analysis on the dynamics of the two models. The results reveal that the 3-D model and 4-model demonstrate opposite patterns for trophic cascade in terms of the dependence of population sizes for each species at the co-existence equilibrium on the anti-predation response level parameter, and such a difference is attributed to whether or not there is a benefit for the anti-predation response by the meso-carnivore species.

Kinetics and Mechanism of Ecochemical Processes

2020 ◽  
pp. 109-136
Author(s):  
Sergey Olegovich Travin
Keyword(s):  
Mathematical Modeling ◽  
Numerical Experiment ◽  
Food Chain ◽  
Exponential Growth ◽  
Natural Waters ◽  
Stationary States ◽  
The Cost ◽  
Physical And Chemical ◽  
The Impact

Significant efforts of mankind and huge funds were spent to study the mechanisms of environmental processes. Recent decades have been marked by exponential growth of computer power and the accompanying decrease in the cost of computing. With regard to the mathematical modeling of physical and chemical processes that determine the quality of natural waters, atmosphere, and soil, this has led to the development of an extensive approach based on an increase in the number of components and reactions between them taken into consideration. In this chapter, the authors describe features of ecochemical systems and discuss the moments that complicates their prediction. Using the method of numerical experiment, they investigate the behavior of periodic systems with multiple stationary states. One conclusion is that the actual manifestation cannot be used to determine at what stage the impact occurred and to what stage of the food chain it relates. Another conclusion is that systems involving multiple stationary states are prone to bifurcations and chaotic jumps from one limit cycle to another.

Demonstrating Nutrient Cost Gradients: A Brooklyn Case Study

2014 ◽  
Vol 84 (5-6) ◽  
pp. 244-251 ◽  
Author(s):  
Robert J. Karp ◽  
Gary Wong ◽  
Marguerite Orsi
Keyword(s):  
Low Income ◽  
Energy Content ◽  
Food Selection ◽  
The United States ◽  
United States Department ◽  
Micronutrient Deficiencies ◽  
Caloric Density ◽  
Low Income Families ◽  
The Cost ◽  
The Impact

Abstract. Introduction: Foods dense in micronutrients are generally more expensive than those with higher energy content. These cost-differentials may put low-income families at risk of diminished micronutrient intake. Objectives: We sought to determine differences in the cost for iron, folate, and choline in foods available for purchase in a low-income community when assessed for energy content and serving size. Methods: Sixty-nine foods listed in the menu plans provided by the United States Department of Agriculture (USDA) for low-income families were considered, in 10 domains. The cost and micronutrient content for-energy and per-serving of these foods were determined for the three micronutrients. Exact Kruskal-Wallis tests were used for comparisons of energy costs; Spearman rho tests for comparisons of micronutrient content. Ninety families were interviewed in a pediatric clinic to assess the impact of food cost on food selection. Results: Significant differences between domains were shown for energy density with both cost-for-energy (p < 0.001) and cost-per-serving (p < 0.05) comparisons. All three micronutrient contents were significantly correlated with cost-for-energy (p < 0.01). Both iron and choline contents were significantly correlated with cost-per-serving (p < 0.05). Of the 90 families, 38 (42 %) worried about food costs; 40 (44 %) had chosen foods of high caloric density in response to that fear, and 29 of 40 families experiencing both worry and making such food selection. Conclusion: Adjustments to USDA meal plans using cost-for-energy analysis showed differentials for both energy and micronutrients. These differentials were reduced using cost-per-serving analysis, but were not eliminated. A substantial proportion of low-income families are vulnerable to micronutrient deficiencies.

Characterizing the impact of recovering sea otters on commercially important crabs in California estuaries

2020 ◽  
Vol 655 ◽  
pp. 123-137
Author(s):  
TM Grimes ◽  
MT Tinker ◽  
BB Hughes ◽  
KE Boyer ◽  
L Needles ◽  
...  
Keyword(s):  
Abiotic Factors ◽  
Sea Otter ◽  
Dungeness Crab ◽  
Sea Otters ◽  
Elkhorn Slough ◽  
Enhydra Lutris Nereis ◽  
Crab Abundance ◽  
Population Sizes ◽  
Commercially Important ◽  
The Impact

Protective legislation and management have led to an increase in California’s sea otter Enhydra lutris nereis population. While sea otter recovery has been linked to ecosystem benefits, sea otter predation may negatively affect commercially valuable species. Understanding the potential influence of sea otters is of particular importance as their range expands into estuaries that function as nurseries for commercially valuable species like Dungeness crab Metacarcinus magister. We consider how sea otter predation has affected the abundance and size of juvenile Dungeness crab in Elkhorn Slough, California, USA, and analyzed cancrid crab abundance and size across 4 California estuaries with and without sea otters to understand how biotic and abiotic factors contribute to observed variation in crab size and abundance. We compared trends in southern sea otters relative to Dungeness crab landings in California to assess whether increasing sea otter abundance have negatively impacted landings. In Elkhorn Slough, juvenile Dungeness crab abundance and size have declined since 2012, coinciding with sea otter population growth. However, the impact of sea otters on juvenile Dungeness crab size was habitat-specific and only significant in unvegetated habitat. Across estuaries, we found that cancrid crab abundance and size were negatively associated with sea otter presence. While abiotic factors varied among estuaries, these factors explained little of the observed variation in crab abundance or size. Although we found evidence that sea otters can have localized effects on cancrid crab populations within estuaries, we found no evidence that southern sea otters, at recent population sizes, have negatively impacted Dungeness crab landings in California from 2000-2014.

TRANSFER FİYATLAMA UYGULAMASININ İŞLETME PERFORMANSINA ETKİSİ VE VERGİSEL AÇIDAN DEĞERLENDİRİLMESİ

2014 ◽  
Vol 1 (2) ◽  
pp. 187
Author(s):  
Serdar KUZU
Keyword(s):  
Business Performance ◽  
Transfer Pricing ◽  
Tax Law ◽  
Economic Activities ◽  
Tax System ◽  
Goods And Services ◽  
Tax Legislation ◽  
International Transactions ◽  
The Cost ◽  
The Impact

The size of international trade continues to extend rapidly from day to day as a result of the globalization process. This situation causes an increase in the economic activities of businesses in the trading area. One of the main objectives of the cost system applied in businesses is to be able to monitor the competitors and the changes that can be occured as a result of the developments in the sector. Thus, making cost accounting that is proper according to IAS / IFRS and tax legislation has become one of the strategic targets of the companies in most countries. In this respect, businesses should form their cost and pricing systems according to new regulations. Transfer pricing practice is usefull in setting the most proper price for goods that are subject to the transaction, in evaluating the performance of the responsibility centers of business, and in determining if the inter-departmental pricing system is consistent with targets of the business. The taxing powers of different countries and also the taxing powers of different institutions in a country did not overlap. Because of this reason, bringing new regulations to the tax system has become essential. The transfer pricing practice that has been incorporated into the Turkish Tax System is one of the these regulations. The transfer pricing practice which includes national and international transactions has been included in the Corporate Tax Law and Income Tax Law. The aim of this study is to analyse the impact of goods and services transfer that will occur between departments of businesses on the responsibility center and business performance, and also the impact of transfer pricing practice on the business performance on the basis of tax-related matters. As a result of the study, it can be said that transfer pricing practice has an impact on business performance in terms of both price and tax-related matters.

Return on Invesment (ROI) of Software Product: A Systematic Literature Review

2015 ◽  
Vol 6 (1) ◽  
pp. 50-57
Author(s):  
Rizqa Raaiqa Bintana ◽  
Putri Aisyiyah Rakhma Devi ◽  
Umi Laili Yuhana
Keyword(s):  
Return On Investment ◽  
Assessment Criteria ◽  
Software Product ◽  
And Performance ◽  
Rational Consideration ◽  
Actual Return ◽  
The Cost ◽  
Investment Models ◽  
The Impact

The quality of the software can be measured by its return on investment. Factors which may affect the return on investment (ROI) is the tangible factors (such as the cost) dan intangible factors (such as the impact of software to the users or stakeholder). The factor of the software itself are assessed through reviewing, testing, process audit, and performance of software. This paper discusses the consideration of return on investment (ROI) assessment criteria derived from the software and its users. These criteria indicate that the approach may support a rational consideration of all relevant criteria when evaluating software, and shows examples of actual return on investment models. Conducted an analysis of the assessment criteria that affect the return on investment if these criteria have a disproportionate effort that resulted in a return on investment of a software decreased. Index Terms - Assessment criteria, Quality assurance, Return on Investment, Software product

Modelling the cost of ill health in Health&WealthMOD (Version II): lost labour force participation, income and taxation, and the impact of disease prevention

2010 ◽  
Vol 4 (3) ◽  
pp. 32-36 ◽  
Author(s):  
Deborah Schofield ◽  
Rupendra Shrestha ◽  
Emily Callander ◽  
Richard Pervical ◽  
Simon Kelly ◽  
...  
Keyword(s):  
Disease Prevention ◽  
Labour Force ◽  
Labour Force Participation ◽  
The Cost ◽  
The Impact

ECONOMIC SUBSTANTIATION OF TRANSITION TO PERSONNEL OUTSOURCING IN THE ORGANIZATIONS OF THE CONSTRUCTION INDUSTRY

2020 ◽  
pp. 70-79
Author(s):  
V.V. Verna
Keyword(s):  
Cost Effectiveness ◽  
Construction Industry ◽  
Methodological Approaches ◽  
Construction Organization ◽  
The Cost ◽  
The Impact

The article provides a rationale for methodological approaches to assessing the effectiveness of outsourcing in organizations of the construction industry using the example of outsourcing schemes to perform personnel functions. The conditional example shows the impact of the use of outsourcing on reducing the costs of a construction organization. The main prerequisites for the use of outsourcing in the activities of enterprises in the construction industry are identified, methodological approaches to assessing the cost-effectiveness of personnel outsourcing in the construction industry enterprises are substantiated.

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