scholarly journals Effects of Vector Maturation Time on the Dynamics of Cassava Mosaic Disease

2021 ◽  
Vol 83 (8) ◽  
Author(s):  
F. Al Basir ◽  
Y. N. Kyrychko ◽  
K. B. Blyuss ◽  
S. Ray
Keyword(s):  
Time Delay ◽  
Plant Density ◽  
Plant Viruses ◽  
Mosaic Disease ◽  
Plant Diseases ◽  
Cassava Mosaic Disease ◽  
Maturation Time ◽  
Negative Effect ◽  
Dynamical Regimes

AbstractMany plant diseases are caused by plant viruses that are often transmitted to plants by vectors. For instance, the cassava mosaic disease, which is spread by whiteflies, has a significant negative effect on plant growth and development. Since only mature whiteflies can contribute to the spread of the cassava mosaic virus, and the maturation time is non-negligible compared to whitefly lifetime, it is important to consider the effects this maturation time can have on the dynamics. In this paper, we propose a mathematical model for dynamics of cassava mosaic disease that includes immature and mature vectors and explicitly includes a time delay representing vector maturation time. A special feature of our plant epidemic model is that vector recruitment is negatively related to the delayed ratio between vector density and plant density. We identify conditions of biological feasibility and stability of different steady states in terms of system parameters and the time delay. Numerical stability analyses and simulations are performed to explore the role of various parameters, and to illustrate the behaviour of the model in different dynamical regimes. We show that the maturation delay may stabilise epidemiological dynamics that would otherwise be cyclic.

scholarly journals The role of interference between vectors in control of plant diseases

2021 ◽  
Author(s):  
Marta Zaffaroni ◽  
Loup Rimbaud ◽  
Ludovic Mailleret ◽  
Nik Cunniffe ◽  
Daniele Bevacqua
Keyword(s):  
Disease Transmission ◽  
Management Strategies ◽  
Viral Disease ◽  
Plant Viruses ◽  
Plant Diseases ◽  
Agronomic Practices ◽  
Ecological Principles ◽  
Single Host ◽  
Primary Vector

Aphids are the primary vector of plant viruses. Transient aphids, which probe several plants per day, are considered to be the principal vectors of non-persistently transmitted (NPT) viruses. However, resident aphids, which can complete their life cycle on a single host and are affected by agronomic practices, can transmit NPT viruses as well. Moreover, they can interfere both directly and indirectly with transient aphids, eventually shaping plant disease dynamics. By mean of an epidemiological model, originally accounting for ecological principles and agronomic practices, we explore the consequences of fertilization and irrigation, pesticide deployment and roguing of infected plants on the spread of viral disease in crops. Our results indicate that the spread of NPT viruses can be i) both reduced or increased by fertilization and irrigation, depending on whether the interference is direct or indirect; ii) counter-intuitively increased by pesticide application and iii) reduced by roguing infected plants. We show that a better understanding of vectors' interactions would enhance our understanding of disease transmission, supporting the development of disease management strategies.

Social Motives Predict Loneliness During a Developmental Transition

2017 ◽  
Vol 76 (4) ◽  
pp. 145-153 ◽  
Author(s):  
Jana Nikitin ◽  
Alexandra M. Freund
Keyword(s):  
Social Relationships ◽  
Well Being ◽  
Social Avoidance ◽  
Social Approach ◽  
Social Motives ◽  
Developmental Transitions ◽  
Avoidance Motivation ◽  
Negative Effect ◽  
Low Levels

Abstract. Establishing new social relationships is important for mastering developmental transitions in young adulthood. In a 2-year longitudinal study with four measurement occasions (T1: n = 245, T2: n = 96, T3: n = 103, T4: n = 85), we investigated the role of social motives in college students’ mastery of the transition of moving out of the parental home, using loneliness as an indicator of poor adjustment to the transition. Students with strong social approach motivation reported stable and low levels of loneliness. In contrast, students with strong social avoidance motivation reported high levels of loneliness. However, this effect dissipated relatively quickly as most of the young adults adapted to the transition over a period of several weeks. The present study also provides evidence for an interaction between social approach and social avoidance motives: Social approach motives buffered the negative effect on social well-being of social avoidance motives. These results illustrate the importance of social approach and social avoidance motives and their interplay during developmental transitions.

THE NOTHING THAT REALLY IS!

2016 ◽  
Vol 12 (1) ◽  
pp. 4172-4177
Author(s):  
Abdul Malek
Keyword(s):  
Quantum Dynamics ◽  
Theoretical Physics ◽  
Historical Evolution ◽  
Proper Understanding ◽  
Physical Universe ◽  
Wave Particle Duality ◽  
Negative Effect ◽  
Materialist Interpretation

The denial of the existence of contradiction is at the root of all idealism in epistemology and the cause for alienations.  This alienation has become a hindrance for the understanding of the nature and the historical evolution mathematics itself and its role as an instrument in the enquiry of the physical universe (1). A dialectical materialist approach incorporating  the role of the contradiction of the unity of the opposites, chance and necessity etc., can provide a proper understanding of the historical evolution of mathematics and  may ameliorate  the negative effect of the alienation in modern theoretical physics and cosmology. The dialectical view also offers a more plausible materialist interpretation of the bewildering wave-particle duality in quantum dynamics (2).

Peran Badan Pengendalian Dampak Lingkungan dalam Pengendalian Dampak Pencemaran Kegiatan Industri di Kota Batam tahun 2011-2014

2015 ◽  
Vol 14 (1) ◽  
pp. 20
Author(s):  
Wan Asrida ◽  
Dian Arival Aryadana
Keyword(s):  
Environmental Impact ◽  
Environmental Pollution ◽  
Pollution Control ◽  
Control Agency ◽  
Accurate Method ◽  
Industrial Activity ◽  
Research Issues ◽  
Negative Effect ◽  
Research Show

This research is intended to find out the role of the regional environmental impact Control Agency of Batam City against the environmental problems that occur in industrial areas namely, Batam city, concerning sustainable development based upon the environment, the activities of the industry now aims to build an economic sector but has a negative effect that is the pollution of the environment. In this case in Batam city frequent occurrence of environmental pollution caused by industrial activity namely with disposal of waste which are not in place. This research is focused on environmental impact Control Agency area of Batam city authorities in the control of the environment . With the outline of the research issues namely how environmental impact Control Agency the role of the Regions in the control of pollution of the environment against industrial activity in Batam city in 2011-2014 and the factors restricting the role of the regional environmental impact Control Agency in controlling environmental pollution in Batam city in 2011-2014.Type of this research is a descriptive i.e. researchers provide a description and overview of the phenomenon or social symptoms examined by independent variables described in a systematic and accurate. Method of data collection is done by means of interviews and the documentation.The results of this research show that the role of environmental impact Control Agency area of Batam city in pollution control against industrial activity carried out according to its function but have not run well in accordance with the goals and targets that have been set. This is not in accordance with the duties and functions of the regional environmental impact Control Agency of Batam city, resulting in less the maximum role of Bapedalda itself in controlling pollution that occurred in Batam city. So it should be should be able to stake Bapedalda holder which is professional in the discharge of pollution control and must be capable of tackling the obstacles faced.

The path of support-to-sales: mediating role of seller collaborative information exchange in social commerce

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Li Chen ◽  
Fengxia Zhu ◽  
Murali Mantrala
Keyword(s):  
Information Exchange ◽  
Instrumental Support ◽  
Trade Volume ◽  
Social Commerce ◽  
Content Type ◽  
Mediating Role ◽  
The Social ◽  
Source Data ◽  
Negative Effect

Purpose This paper aims to systematically investigate the direct and indirect effects of four types of support – peer instrumental support, peer emotional support, platform business support and platform communication support – on seller trade volume in social commerce. It also aims to uncover the path of support-to-sales of the seller from a platform perspective and provides a more complete picture of the social commerce phenomenon. Design/methodology/approach This paper uses multi-source data including primary survey data and secondary data on trade volume to test the hypotheses. PROCESS mediation model is used to analyze the multi-source data set. Findings This study finds that the positive effects of peer instrumental support, platform business support and platform communication support on seller trade volume are fully mediated by seller collaborative information exchange. Also, peer emotional support has a significant negative effect on seller trade volume and collaborative information exchange can serve as a buffer to mitigate the negative effect. Research limitations/implications The authors provide new insights into what types of support are or are not conducive to improving transaction volume of individual sellers and highlight the mediating role of seller information exchange in this value generation process in social commerce. These findings advance current knowledge of how seller interactions increase value in social commerce. The chosen research setting may limit the generalizability of the findings of this study. Practical implications This paper offers valuable implications for social commerce platforms on how to better serve their sellers to achieve high growth. Specifically, the findings suggest that platforms should encourage instrumental support and information exchange among peer sellers. In addition, platforms should expand seller support from a single-focus on sellers’ business to a dual-focus on both sellers’ business and socialization in social commerce. Originality/value This paper fulfills an identified need to study how sellers can better derive value from the social interactions and how social commerce platforms can effectively influence transactions, support sales and serve as a selling platform.

scholarly journals The Role of Fungi in the Cocoa Production Chain and the Challenge of Climate Change

2021 ◽  
Vol 7 (3) ◽  
pp. 202
Author(s):  
Johannes Delgado-Ospina ◽  
Junior Bernardo Molina-Hernández ◽  
Clemencia Chaves-López ◽  
Gianfranco Romanazzi ◽  
Antonello Paparella
Keyword(s):  
Climate Change ◽  
Fungal Infections ◽  
Close Association ◽  
Pathogenic Fungi ◽  
Fungal Species ◽  
Mitigation Strategies ◽  
Plant Diseases ◽  
Production Chain ◽  
Cocoa Production

Background: The role of fungi in cocoa crops is mainly associated with plant diseases and contamination of harvest with unwanted metabolites such as mycotoxins that can reach the final consumer. However, in recent years there has been interest in discovering other existing interactions in the environment that may be beneficial, such as antagonism, commensalism, and the production of specific enzymes, among others. Scope and approach: This review summarizes the different fungi species involved in cocoa production and the cocoa supply chain. In particular, it examines the presence of fungal species during cultivation, harvest, fermentation, drying, and storage, emphasizing the factors that possibly influence their prevalence in the different stages of production and the health risks associated with the production of mycotoxins in the light of recent literature. Key findings and conclusion: Fungi associated with the cocoa production chain have many different roles. They have evolved in a varied range of ecosystems in close association with plants and various habitats, affecting nearly all the cocoa chain steps. Reports of the isolation of 60 genera of fungi were found, of which only 19 were involved in several stages. Although endophytic fungi can help control some diseases caused by pathogenic fungi, climate change, with increased rain and temperatures, together with intensified exchanges, can favour most of these fungal infections, and the presence of highly aggressive new fungal genotypes increasing the concern of mycotoxin production. For this reason, mitigation strategies need to be determined to prevent the spread of disease-causing fungi and preserve beneficial ones.

scholarly journals Drought and Salinity in Citriculture: Optimal Practices to Alleviate Salinity and Water Stress

Agronomy ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1283
Author(s):  
Vasileios Ziogas ◽  
Georgia Tanou ◽  
Giasemi Morianou ◽  
Nektarios Kourgialas
Keyword(s):  
Agricultural Sector ◽  
Review Paper ◽  
Cell Metabolism ◽  
High Water ◽  
Crop Productivity ◽  
Fruit Tree ◽  
Key Factors ◽  
Negative Effect

Among the various abiotic stresses, drought is the major factor limiting crop productivity worldwide. Citrus has been recognized as a fruit tree crop group of great importance to the global agricultural sector since there are 140 citrus-producing countries worldwide. The majority of citrus-producing areas are subjected to dry and hot summer weather, limited availability of water resources with parallel low-quality irrigation water due to increased salinity regimes. Citrus trees are generally classified as “salt-intolerant” with high water needs, especially during summer. Water scarcity negatively affects plant growth and impairs cell metabolism, affecting the overall tree growth and the quality of produced fruit. Key factors that overall attempt to sustain and withstand the negative effect of salinity and drought stress are the extensive use of rootstocks in citriculture as well as the appropriate agronomical and irrigation practices applied. This review paper emphasizes and summarizes the crucial role of the above factors in the sustainability of citriculture.

scholarly journals Up to No Good? Gender, Social Impact Work, and Employee Promotions

2021 ◽  
pp. 000183922110206
Author(s):  
Christiane Bode ◽  
Michelle Rogan ◽  
Jasjit Singh
Keyword(s):  
Panel Data ◽  
Social Impact ◽  
Male Gender ◽  
Decision Makers ◽  
Gender Beliefs ◽  
Negative Effect ◽  
Male Gender Role ◽  
Promotion Rates ◽  
Vignette Experiment

Firms increasingly offer employees the opportunity to participate in firm-sponsored social impact initiatives expected to benefit the firm and employees. We argue that participation in such initiatives hinders employees’ advancement in their firms by reducing others’ perceptions of their fit and commitment. Because social impact work is more congruent with female than male gender role stereotypes, promotion rates will be lower for participating men, and male evaluators will be less likely than female evaluators to recommend promotion for male participants. Using panel data on 1,379 employees of a consulting firm, we find significantly lower promotion rates for male participants relative to female participants, female non-participants, and male non-participants. A vignette experiment involving 893 managers shows that lower promotion rates are due to lower perceptions of fit, but not commitment, and greater bias against male participants by male evaluators. Taken together, the results of the two studies suggest that the negative effect of participation on promotion is conditional upon participant and evaluator gender, underscoring the role of gender in evaluation of social impact work. In settings in which decision makers are predominately male, gender beliefs may limit male employees’ latitude to contribute to the firm’s social impact agenda.

scholarly journals Natural Disasters and Economic Growth: The Mitigating Role of Microfinance Institutions

2021 ◽  
Vol 13 (9) ◽  
pp. 5055
Author(s):  
John Sseruyange ◽  
Jeroen Klomp
Keyword(s):  
Developing Countries ◽  
Natural Disasters ◽  
Legal Status ◽  
Agricultural Sector ◽  
Banking System ◽  
Fe Model ◽  
Microfinance Institutions ◽  
Natural Event ◽  
Negative Effect

In this study, we explore whether microfinance institutions (MFIs) can mitigate the adverse macroeconomic consequences of natural disasters. The provision of capital immediately following a natural event is recognized as one of the necessary conditions for a fast economic recovery. However, one concern is that a large majority of natural disasters occur in developing countries where households and the private sector have only limited access to the formal banking system. As an alternative, MFIs may fill up this gap in providing liquidity in the form of microcredit. The existing evidence on how MFIs respond to disaster effects is foremost based on case and micro-level evidence. In turn, the focus of this study is more on the macro impact of MFI activities after a natural disaster. Based on the finding obtained from an OLS-FE model using an unbalanced panel considering more than 80 developing countries and emerging economies, we can conclude that natural disasters harm macroeconomic performance primarily through their effect on the agricultural sector. However, access to lending facilities from MFIs mitigates a large part of this negative effect. Moreover, the extent to which MFIs are able to mitigate these effects depends to a great extent on their nature, i.e., their organizational structure, profitability, legal status, age, and the number of clients they serve.

Time Delay Effects on Compactability of Soil-Cement Materials during Proctor Testing

2021 ◽  
pp. 036119812199870
Author(s):  
W. Griffin Sullivan ◽  
Isaac L. Howard
Keyword(s):  
Time Delay ◽  
Vital Role ◽  
Test Method ◽  
Dry Density ◽  
Soil Cement ◽  
Delay Effects ◽  
Proctor Test ◽  
Negative Effect ◽  
Departments Of Transportation ◽  
Cement Mixtures

The Proctor test method, as specified in AASHTO T134 and ASTM D558, continues to play a vital role in design and construction quality control for soil-cement materials. However, neither test method establishes a methodology or standardized protocols to characterize the effects of time delay between cement addition and compaction, also known as compaction delay. Compaction delay has been well documented to have a notably negative effect on compactability, compressive strength, and overall performance of soil-cement materials, but specification tools to address this behavior are not prevalent. This paper aims to demonstrate the extent of compaction delay effects on several soil-cement mixtures used in Mississippi and to present recommended new test method protocols for AASHTO T134 to characterize compaction delay effects. Data presented showed that not all soil-cement mixtures are sensitive to compaction delay, but some mixtures can be very sensitive and lead to a meaningful decrease in specimen dry density. Recommended test method protocols were presented for AASHTO T134 and commentary was presented to provide state Departments of Transportation and other specifying agencies a few examples of how the new compaction delay protocols could be implemented.

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