scholarly journals Food Webs Over Time: Evaluating the Variability of Degree Distribution on Ecological Networks

2017 ◽  
Author(s):  
Daniela N Lopez ◽  
Patricio A Camus ◽  
Nelson Valdivia ◽  
Sergio A Estay
Keyword(s):  
Food Webs ◽  
Functional Form ◽  
Exponential Model ◽  
Ecological Networks ◽  
Specific Interactions ◽  
Distribution Models ◽  
Networks Analysis ◽  
Topological Characteristics ◽  
Time Specific ◽  
Over Time

AbstractAlthough networks analysis has moved from static to dynamic, ecological networks are still analyzed as time-aggregated units where time-specific interactions are aggregated into one single network. As a result, several questions arise such as what is the functional form of and how variable is the topology of time-specific versus time-aggregated ecological networks? Furthermore, it is yet unknown to what extent the structure of time-aggregated networks is representative of the dynamics of the community. Here, we compared the topology of time-specific and time-aggregated networks by analyzing a set of intertidal networks containing more than 1,000 interactions, and assessed the spatiotemporal dynamics of their degree distributions. By fitting different distribution models, we found that the out-degree distributions of seasonal and time-aggregated networks were best described by an exponential model while the in-degree distributions were best described by a discrete generalized beta model. The degree distributions of the seasonal networks were highly temporally variable and are significantly different from those of time-aggregated networks. We observed that seasonal degree distributions converged toward time-aggregated network distributions after 1.5 years of sampling. Our results highlight the importance of understanding the dynamics of ecological networks, which can show topological characteristics significantly different from those of time-aggregated networks.

scholarly journals CO<sub>2</sub> flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

2007 ◽  
Vol 4 (6) ◽  
pp. 1005-1025 ◽  
Author(s):  
L. Kutzbach ◽  
J. Schneider ◽  
T. Sachs ◽  
M. Giebels ◽  
H. Nykänen ◽  
...  
Keyword(s):  
Linear Regression ◽  
Nonlinear Regression ◽  
Co2 Flux ◽  
Exponential Model ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Closed Chamber ◽  
Exponential Regression ◽  
Closure Time ◽  
Over Time

Abstract. Closed (non-steady state) chambers are widely used for quantifying carbon dioxide (CO2) fluxes between soils or low-stature canopies and the atmosphere. It is well recognised that covering a soil or vegetation by a closed chamber inherently disturbs the natural CO2 fluxes by altering the concentration gradients between the soil, the vegetation and the overlying air. Thus, the driving factors of CO2 fluxes are not constant during the closed chamber experiment, and no linear increase or decrease of CO2 concentration over time within the chamber headspace can be expected. Nevertheless, linear regression has been applied for calculating CO2 fluxes in many recent, partly influential, studies. This approach has been justified by keeping the closure time short and assuming the concentration change over time to be in the linear range. Here, we test if the application of linear regression is really appropriate for estimating CO2 fluxes using closed chambers over short closure times and if the application of nonlinear regression is necessary. We developed a nonlinear exponential regression model from diffusion and photosynthesis theory. This exponential model was tested with four different datasets of CO2 flux measurements (total number: 1764) conducted at three peatlands sites in Finland and a tundra site in Siberia. Thorough analyses of residuals demonstrated that linear regression was frequently not appropriate for the determination of CO2 fluxes by closed-chamber methods, even if closure times were kept short. The developed exponential model was well suited for nonlinear regression of the concentration over time c(t) evolution in the chamber headspace and estimation of the initial CO2 fluxes at closure time for the majority of experiments. However, a rather large percentage of the exponential regression functions showed curvatures not consistent with the theoretical model which is considered to be caused by violations of the underlying model assumptions. Especially the effects of turbulence and pressure disturbances by the chamber deployment are suspected to have caused unexplainable curvatures. CO2 flux estimates by linear regression can be as low as 40% of the flux estimates of exponential regression for closure times of only two minutes. The degree of underestimation increased with increasing CO2 flux strength and was dependent on soil and vegetation conditions which can disturb not only the quantitative but also the qualitative evaluation of CO2 flux dynamics. The underestimation effect by linear regression was observed to be different for CO2 uptake and release situations which can lead to stronger bias in the daily, seasonal and annual CO2 balances than in the individual fluxes. To avoid serious bias of CO2 flux estimates based on closed chamber experiments, we suggest further tests using published datasets and recommend the use of nonlinear regression models for future closed chamber studies.

scholarly journals Patterns of anxiety and distress over 12 months following participation in HPV primary screening

2021 ◽  
pp. sextrans-2020-054780
Author(s):  
Laura A V Marlow ◽  
Emily McBride ◽  
Deborah Ridout ◽  
Alice S Forster ◽  
Henry Kitchener ◽  
...  
Keyword(s):  
Positive Result ◽  
Short Form ◽  
Cervical Screening ◽  
General Health Questionnaire ◽  
Psychological Impact ◽  
Control Group ◽  
Abnormal Cytology ◽  
Normal Cytology ◽  
Time Specific ◽  
Over Time

ObjectivesMany countries are now using primary human papillomavirus (HPV) testing for cervical screening, testing for high-risk HPV and using cytology as triage. An HPV-positive result can have an adverse psychological impact, at least in the short term. In this paper, we explore the psychological impact of primary HPV screening over 12 months.MethodsWomen were surveyed soon after receiving their results (n=1133) and 6 (n=762) and 12 months (n=537) later. Primary outcomes were anxiety (Short-Form State Anxiety Inventory-6) and distress (General Health Questionnaire-12). Secondary outcomes included concern, worry about cervical cancer and reassurance. Mixed-effects regression models were used to explore differences at each time point and change over time across four groups according to their baseline result: control (HPV negative/HPV cleared/normal cytology and not tested for HPV); HPV positive with normal cytology; HPV positive with abnormal cytology; and HPV persistent (ie, second consecutive HPV-positive result).ResultsWomen who were HPV positive with abnormal cytology had the highest anxiety scores at baseline (mean=42.2, SD: 15.0), but this had declined by 12 months (mean=37.0, SD: 11.7) and was closer to being within the ‘normal’ range (scores between 34 and 36 are considered ‘normal’). This group also had the highest distress at baseline (mean=3.3, SD: 3.8, scores of 3+ indicate case-level distress), but the lowest distress at 12 months (mean=1.9, SD: 3.1). At 6 and 12 months, there were no between-group differences in anxiety or distress for any HPV-positive result group when compared with the control group. The control group were less concerned and more reassured about their result at 6 and 12 months than the HPV-positive with normal cytology group.ConclusionsOur findings suggest the initial adverse impact of an HPV-positive screening result on anxiety and distress diminishes over time. Specific concerns about the result may be longer lasting and efforts should be made to address them.

scholarly journals Reconstruction of plant–pollinator networks from observational data

2019 ◽  
Author(s):  
Jean-Gabriel Young ◽  
Fernanda S. Valdovinos ◽  
M. E. J. Newman
Keyword(s):  
Food Webs ◽  
Observational Data ◽  
Network Structure ◽  
Rare Species ◽  
Statistical Technique ◽  
Ecological Networks ◽  
Statistical Analyses ◽  
Published Data ◽  
Statistical Errors ◽  
Plant Pollinator

Empirical measurements of ecological networks such as food webs and mutualistic networks are often rich in structure but also noisy and error-prone, particularly for rare species for which observations are sparse. Focusing on the case of plant–pollinator networks, we here describe a Bayesian statistical technique that allows us to make accurate estimates of network structure and ecological metrics from such noisy observational data. Our method yields not only estimates of these quantities, but also estimates of their statistical errors, paving the way for principled statistical analyses of ecological variables and outcomes. We demonstrate the use of the method with an application to previously published data on plant–pollinator networks in the Seychelles archipelago, calculating estimates of network structure, network nestedness, and other characteristics.

Culture inside: Scale, intimacy, and chronotopic stance in situated narratives

2020 ◽  
pp. 1-23
Author(s):  
Sonya E. Pritzker ◽  
Sabina Perrino
Keyword(s):  
Linguistic Anthropology ◽  
Northern Italy ◽  
Specific Interactions ◽  
Embodied Experience ◽  
Time And Space ◽  
Discursive Strategies ◽  
Ethnographic Studies ◽  
Zoom In ◽  
Beijing China ◽  
Over Time

ABSTRACT This article focuses on what we define as scalar intimacy in the stories people tell about their embodied experience as sociohistorical beings. Our analysis, based on ethnographic studies in Northern Italy (Perrino) and Beijing, China (Pritzker), examines the ways in which speech participants draw upon various discursive strategies to ‘zoom in’ and ‘pan out’ of both time and space, placing themselves and their activities in relation to various people, ideologies, and practices. Scalar intimacy, we argue, provides a novel framework for understanding the multiple ways in which people use language to scale their embodied experience in relation to culturally situated ideas and forms. Scalar intimacy thus extends the study of scales and fractal recursivity in linguistic anthropology and sociolinguistics. It also contributes to scholarship focusing on how culturally situated meanings are reproduced and challenged over time through specific interactions. (China, chronotope, identity, intimacy, narrative, Northern Italy, scales)*

scholarly journals The development of small settlements in the industrial plant - city model - based on the examples of Nowa Dęba and Nowa Sarzyna

2018 ◽  
Vol 45 ◽  
pp. 00079 ◽  
Author(s):  
Anna Sikora
Keyword(s):  
Industrial Plant ◽  
Urban Centers ◽  
Small Cities ◽  
Industrial Facilities ◽  
Industrial Plants ◽  
Spatial Changes ◽  
City Model ◽  
Post War ◽  
Time Specific ◽  
Over Time

Double-purpose industrial plant-settlement complexes (city) are fairly popular urban combinations; especially so during the inter-war and post-war industrial periods, when through a decision by the central authorities, industrial facilities were located in specific areas which were then developed over time. Specific cases of such complexes are two small cities built from scratch around growing industrial plants. The article presents certain functional and spatial changes in two urban centers: Nowa Dęba and Nowa Sarzyna, which are located in the Subcarpathian Voivodeship.

The Structure of Ecological Networks Across Levels of Organization

2020 ◽  
Vol 51 (1) ◽  
pp. 433-460 ◽  
Author(s):  
Paulo R. Guimarães
Keyword(s):  
Food Webs ◽  
Ecological Systems ◽  
Ecological Networks ◽  
Ecological Communities ◽  
Ecological Interactions ◽  
Biological Organization ◽  
Architectural Patterns ◽  
Fundamental Challenge ◽  
Spatiotemporal Scales ◽  
Multiple Levels

Interactions connect the units of ecological systems, forming networks. Individual-based networks characterize variation in niches among individuals within populations. These individual-based networks merge with each other, forming species-based networks and food webs that describe the architecture of ecological communities. Networks at broader spatiotemporal scales portray the structure of ecological interactions across landscapes and over macroevolutionary time. Here, I review the patterns observed in ecological networks across multiple levels of biological organization. A fundamental challenge is to understand the amount of interdependence as we move from individual-based networks to species-based networks and beyond. Despite the uneven distribution of studies, regularities in network structure emerge across scales due to the fundamental architectural patterns shared by complex networks and the interplay between traits and numerical effects. I illustrate the integration of these organizational scales by exploring the consequences of the emergence of highly connected species for network structures across scales.

scholarly journals Functional intersection of the kallikrein-related peptidases (KLKs) and thrombostasis axis

2010 ◽  
Vol 391 (4) ◽  
Author(s):  
Michael Blaber ◽  
Hyesook Yoon ◽  
Maria A. Juliano ◽  
Isobel A. Scarisbrick ◽  
Sachiko I. Blaber
Keyword(s):  
Initial Conditions ◽  
Tissue Injury ◽  
Large Body ◽  
Therapeutic Agents ◽  
Specific Interactions ◽  
Complete Understanding ◽  
Functional Interaction ◽  
Regulatory Interactions ◽  
Normal Health ◽  
Over Time

Abstract A large body of emerging evidence indicates a functional interaction between the kallikrein-related peptidases (KLKs) and proteases of the thrombostasis axis. These interactions appear relevant for both normal health as well as pathologies associated with inflammation, tissue injury, and remodeling. Regulatory interactions between the KLKs and thrombostasis proteases could impact several serious human diseases, including neurodegeneration and cancer. The emerging network of specific interactions between these two protease families appears to be complex, and much work remains to elucidate it. Complete understanding how this functional network resolves over time, given specific initial conditions, and how it might be controllably manipulated, will probably contribute to the emergence of novel diagnostics and therapeutic agents for major diseases.

scholarly journals Analysis of wind speed characteristics using different distribution models in Medan City, Indonesia

2021 ◽  
Vol 12 (2) ◽  
pp. 1102
Author(s):  
Suwarno Suwarno ◽  
Ismail Yusuf ◽  
M. Irwanto ◽  
Ayong Hiendro
Keyword(s):  
Wind Speed ◽  
Density Function ◽  
Weibull Model ◽  
Exponential Model ◽  
Distribution Functions ◽  
Cumulative Probability ◽  
Distribution Models ◽  
Shape Factors ◽  
Wind Characteristics ◽  
Wind Distribution

<span lang="EN-CA">Estimating wind speed characteristics plays an essential role in designing a wind power plant at a selected location. In this study, the Weibull, gamma, and exponential distribution models were proposed to estimate and analyze the wind speed parameters and distribution functions. Real measured data were collected from Medan City, Indonesia. The scale and shape factors of wind distribution for three years data were calculated. The observed cumulative probability of the three models was compared to predicted wind characteristics. The probability density function (PDF) and the cumulative density function (CDF) of wind speed were also analyzed. The results showed that the Weibull model was the best model to determine PDF, while the exponential model was the best model to determine CDF for the Medan City wind site.</span>

Sign in / Sign up

Export Citation Format

Share Document