The paradox of the “paradox of the plankton”

2013 ◽  
Vol 71 (2) ◽  
pp. 236-240 ◽  
Author(s):  
Nicholas R. Record ◽  
Andrew J. Pershing ◽  
Frédéric Maps
Keyword(s):  
Environmental Variables ◽  
Competitive Exclusion ◽  
Type Systems ◽  
Community Level ◽  
Limited Resources ◽  
Additional Parameter ◽  
Ecosystem Models ◽  
The Past ◽  
Systems Of Differential Equations ◽  
Ocean Ecosystem

Abstract Record, N. R., Pershing, A. J., and Maps, F. 2014. The paradox of the “paradox of the plankton”. – ICES Journal of Marine Science, 71: 236–240. One of the central orienting questions in biodiversity theory and ecology is the “paradox of the plankton”, which asks how it is possible for many species to coexist on limited resources given the tendency for competition to exclude species. Over the past five decades, ecologists have offered dozens of solutions to the paradox, invoking game theory, chaos, stochastics, and many other concepts. Despite the plentitude of solutions to the paradox, ecologists continue to offer up novel solutions. Ocean modellers are now faced with the opposite paradox: given the overabundance and the diversity of solutions to the paradox, what is the appropriate way to build coexistence into ecosystem models? Ocean ecosystem models have a very standardized form—nutrient–phytoplankton–zooplankton (NPZ)-type systems of differential equations—where competitive exclusion is a common model behaviour. We suggest approaching the problem from the perspective of community-level patterns. We offer a prototype for building coexistence into NPZ models. The model allows for diverse assemblages of phytoplankton or zooplankton groups to persist and produces accurate community-level patterns. The approach is simple, adding only one additional parameter, and allows us to test the effects of trait distributions and environmental variables on diversity.

Use of bioclimatic analysis to direct survey effort for the long-footed potoroo (Potorous longipes), a rare forest-dwelling rat-kangaroo

2002 ◽  
Vol 29 (2) ◽  
pp. 193 ◽  
Author(s):  
A. W. Claridge
Keyword(s):  
Environmental Variables ◽  
New Records ◽  
New South ◽  
New South Wales ◽  
Geographic Range ◽  
Suitable Habitat ◽  
The Past ◽  
South Wales ◽  
North Eastern ◽  
Survey Effort

The long-footed potoroo (Potorous longipes) is one of the rarest and most elusive forest-dwelling mammals in Australia. Survey effort for the species over the past decade or so in south-eastern New South Wales has been driven, primarily, by predictions derived from climatic analyses using BIOCLIM. These predictions were based on known locality records of the long-footed potoroo from adjacent East Gippsland, Victoria. While they have proven useful in confirming the occurrence of the species in New South Wales, recent fortuitous records of the species from north-eastern Victoria fall well outside of the range predicted earlier by BIOCLIM. Using these new records a revised predicted range is calculated, enlarging considerably the potential geographic extent of climatically suitable habitat for the species. The results presented here highlight the limitations of BIOCLIM when given locality records of a species from only a portion of its true geographic range. I argue that less emphasis might be based on this approach to direct survey effort for the species in the future. Instead, a range of other environmental variables might be used in combination with BIOCLIM-derived outputs when selecting survey sites. In this way a more representative picture of the distribution of the species may be obtained.

How the Design of a 3D Printer Bridged Engineering Design Processes and the Agile Software Manifesto

2019 ◽  
Author(s):  
Steven Lindberg ◽  
Matthew I. Campbell
Keyword(s):  
Engineering Design ◽  
Design Process ◽  
Limited Resources ◽  
Small Scale ◽  
Design Processes ◽  
The Past ◽  
Engineering Design Process ◽  
Agile Software ◽  
Scale Design

Abstract Individual engineering design projects face different challenges depending on their scale. Instead of dealing with problems of complex multidisciplinary systems, small scale design must overcome issues of limited resources. The philosophy of agile software development has been highly successful in addressing similar issues in the software engineering realm over the past two decades. Through the design and prototyping of a low-budget desktop stereolithography printer, the application of agile principles to engineering design process is explored. The printer’s design is discussed in detail to provide examples of successes and failures when these agile principles are put into practice. The paper concludes with a discussion of how agile principles could be leveraged in engineering design. The approach taken in this paper is more of a longitudinal study of a single design process over a twelve-month period as opposed to rigorous experiments that engage multiple users in short design scenarios. Nonetheless, this case study demonstrates how the application of agile principles can inform, improve, and complement traditional engineering design processes.

Variation of bacterial communities in Muztagh ice core from 1869 to 2000

2020 ◽  
Author(s):  
Yongqin Liu ◽  
Tandong Yao ◽  
Baiqing Xu
Keyword(s):  
Bacterial Community ◽  
Temporal Variation ◽  
Community Composition ◽  
Bacterial Communities ◽  
Environmental Variables ◽  
Climate Changes ◽  
Bacterial Community Composition ◽  
Ice Core ◽  
The Past ◽  
Stage 1

<p>Many studies focusing on the physical and chemical indicators of the ice core reflected the climate changes. However, only few biological indicators indicated the past climate changes which are mainly focused in biomass rather than diversity. How the biodiversity response to the climate change during the past hundred years is still unknow. Glaciers in Mt. Muztagh Ata region are influenced by the year-round westerly circulation. We firstly disclosed annual variations of bacterial community compositions in ice core over the past 130 years from Muztagh Glacier, the western Tibetan Plateau. Temporal variation in bacterial abundance was strongly controlled by DOC, TN, δ<sup>18</sup>O, Ca<sup>2+</sup>, SO<sub>4</sub><sup>2</sup><sup>−</sup>, NH<sub>4</sub><sup>+</sup> and NO<sub>3</sub><sup>−</sup>. Proteobacteria, Actinobacteria and Firmicutes were the three most abundant bacterial phyla, accounting for 49.3%, 21.3% and 11.0% of the total community, respectively. The abundances of Firmicutes and Bacteroidetes pronouncedly increased over time throughout the entire ice core. UPGMA cluster analysis of the bacterial community composition separated the all ice core samples into two main clusters along the temporal variation. The first cluster consisted of samples from 1951 to 2000 and the second cluster contained main samples during the period of 1869-1950. The stage 1 and stage 2 bacterial community dissimilarities increased linearly with time on the basis of the Bray-Curtis distance, indicating a similar temporal–decay relationship between the stage 1 and stage 2 bacterial communities. Of all the environmental variables examined, only DOC and NH<sub>4</sub><sup>+</sup> exhibited very strong negative correlations with bacterial Chao1-richness. <sup>18</sup>O was another important variable in shaping the ice core bacterial community composition and contributed 1.6% of the total variation. Moreover, DistLM analysis indicated that the environmental variables explained more variation in the stage 1 community (20.1%) than that of the stage 2 community (19.9%).</p>

A Climatology and Comparison of Parameters for Significant Tornado Events in the United States

2012 ◽  
Vol 27 (1) ◽  
pp. 106-123 ◽  
Author(s):  
Jeremy S. Grams ◽  
Richard L. Thompson ◽  
Darren V. Snively ◽  
Jayson A. Prentice ◽  
Gina M. Hodges ◽  
...  
Keyword(s):  
United States ◽  
Environmental Variables ◽  
The United States ◽  
Kinematic Parameters ◽  
Convective Systems ◽  
The Past ◽  
Standard Pressure ◽  
Wind Events ◽  
Convective Mode

Abstract A sample of 448 significant tornado events was collected, representing a population of 1072 individual tornadoes across the contiguous United States from 2000 to 2008. Classification of convective mode was assessed from radar mosaics for each event with the majority classified as discrete cells compared to quasi-linear convective systems and clusters. These events were further stratified by season and region and compared with a null-tornado database of 911 significant hail and wind events that occurred without nearby tornadoes. These comparisons involved 1) environmental variables that have been used through the past 25–50 yr as part of the approach to tornado forecasting, 2) recent sounding-based parameter evaluations, and 3) convective mode. The results show that composite and kinematic parameters (whether at standard pressure levels or sounding derived), along with convective mode, provide greater discrimination than thermodynamic parameters between significant tornado versus either significant hail or wind events that occurred in the absence of nearby tornadoes.

scholarly journals Using Vampire with Support for Algebraic Datatypes in Type Soundness Proofs

10.29007/pmmz ◽  
2018 ◽  
Author(s):  
Sylvia Grewe ◽  
André Pacak ◽  
Mira Mezini
Keyword(s):  
Type System ◽  
Type Systems ◽  
First Order ◽  
Domain Specific ◽  
The Past ◽  
Finite Term ◽  
The Individual ◽  
Input Format ◽  
Ongoing Project ◽  
Superposition Calculus

In our ongoing project VeriTaS, we aim at automating soundness proofs for type sys- tems of domain-specific languages. In the past, we successfully used previous Vampire versions for automatically discharging many intermediate proof obligations arising within standard soundness proofs for small type systems. With older Vampire versions, encoding the individual proof problems required manual encoding of algebraic datatypes via the theory of finite term algebras. One of the new Vampire versions now supports the direct specification of algebraic datatypes and integrates reasoning about term algebras into the internally used superposition calculus.In this work, we investigate how many proof problems that typically arise within type soundness proofs different Vampire 4.1 versions can prove. Our test set consists of proof problems from a progress proof of a type system for a subset of SQL. We compare running Vampire 4.1 with our own encodings of algebraic datatypes (in untyped as well as in typed first-order logic) to running Vampire 4.1 with support for algebraic datatypes, which uses SMTLIB as input format. We observe that with our own encodings, Vampire 4.1 still proves more of our input problems. We discuss the differences between our own encoding of algebraic datatypes and the ones used within Vampire 4.1 with support for algebraic datatypes.

scholarly journals Constraining parameters in state-of-the-art marine pelagic ecosystem models – is it actually feasible with typical observations of standing stocks?

2015 ◽  
Vol 12 (1) ◽  
pp. 227-274
Author(s):  
U. Löptien ◽  
H. Dietze
Keyword(s):  
Ocean Circulation ◽  
Carbon Assimilation ◽  
Biogeochemical Model ◽  
Model Parameters ◽  
Additional Parameter ◽  
Ecosystem Models ◽  
Standing Stocks ◽  
Estimation Of Model Parameters ◽  
Model Components ◽  
Parameter Retrieval

Abstract. In a changing climate, marine pelagic biogeochemistry may modulate the atmospheric concentrations of climate-relevant species such as CO2 and N2O. To-date, projections rely on earth system models featuring simple pelagic biogeochemical model components, embedded into 3-D-ocean circulation models. Typically, the nucleus of these biogeochemical components are ecosystem models (i.e., a set of partial differential equations) which describe the interaction between nutrients, phytoplankton, zooplankton, and sinking detritus. Most of these models rely on the hyperbolic Michaelis–Menten (MM) formulation which specifies the limiting effect of light and nutrients on carbon assimilation by autotrophic phytoplankton. The respective MM constants, along with other model parameters, are usually tuned by trial-and-error exercises where the parameters are changed until a "reasonable" similarity with observed standing stocks is achieved. Here, we explore with twin experiments (or synthetic "observations") the demands on observations that allow for a more objective estimation of model parameters. We start with parameter retrieval experiments based on "perfect" (synthetic) observations which we, step by step, distort to approach realistic conditions and finally confirm our findings with real-world observations. In summary, we find that MM constants are especially hard to constrain because even modest noise (10%) inherent to observations may hinder the parameter retrieval already. This is of concern since the MM parameters are key to the model's sensitivity to anticipated changes of the external conditions. Further, we illustrate problems associated with parameter estimation based on sparse observations which reveals (additional) parameter dependencies. Somewhat counter to intuition we find, that more observational data can degrade the ability to constrain certain parameters.

scholarly journals A tentative start: evaluation of alternative forms of care for chronic users of psychiatric services

1991 ◽  
Vol 15 (10) ◽  
pp. 596-598 ◽  
Author(s):  
Stephen Colgan ◽  
Keith Bridges ◽  
Langley Brown ◽  
Brian Faragher
Keyword(s):  
Objective Evaluation ◽  
Psychiatric Services ◽  
Limited Resources ◽  
Rehabilitation Services ◽  
Royal Infirmary ◽  
Small Pilot Study ◽  
Psychiatric Illnesses ◽  
Manchester Royal Infirmary ◽  
The Past ◽  
Rapid Diversification

In the past decade there has been a rapid diversification of services provided for patients with chronic psychiatric illnesses. Although these services are thought to be beneficial for those who use them, there has been little in the way of objective evaluation. As new services begin to compete for the limited resources available, it has been recommended that they should demonstrate their effectiveness. This paper reports a small pilot study on the value of an arts based service known as START (Bridges & Brown, 1989) which won a BBC ‘It's My City’ competition in 1989. It has been a popular component of the rehabilitation services of the Department of Psychiatry, Manchester Royal Infirmary since its inception in 1986.

Structured approach to improving wait times and overall customer service in an oncology outpatient phlebotomy department.

2013 ◽  
Vol 31 (31_suppl) ◽  
pp. 77-77
Author(s):  
Patrick M. Forde ◽  
Kitty Violette ◽  
Karen Maylor ◽  
Barbara Kasecamp ◽  
Beth Rushworth ◽  
...  
Keyword(s):  
Customer Service ◽  
Waiting Times ◽  
Limited Resources ◽  
Wait Times ◽  
Staff Satisfaction ◽  
Work Schedule ◽  
Leadership Positions ◽  
The Past ◽  
Patient Satisfaction Scores ◽  
Structured Approach

77 Background: Demands on the Johns Hopkins phlebotomy service have increased exponentially over the past several years leading to increased patient (pt) waiting times and reduced patient and staff satisfaction. Methods: The goal of our project was to reduce waiting times for outpatient phlebotomy to <30 mins for 90% of pts by May 2013 using a multi-disciplinary lean sigma approach. The following interventions were implemented - Two weekly multidisciplinary lean sigma meetings; Move to set appointment times; Twice daily staff "huddles" to plan the work schedule; Ensure a minimum of 8 phlebotomists on duty daily; Expand training for clinical assistants (CAs) to access VADs; Introduce pager system for pts to reduce needless waiting; Introduce leadership positions among phlebotomy and CA staff to manage change. Results: Within 6 months of these concerted efforts wait times have reduced to <30 mins and patient satisfaction scores for >90% of pts are very good or excellent. Conclusions: Difficult problems such as increasing patient demand with constrained resources can be ameliorated with a multidisciplinary structured approach. The project as outlined may serve as a template for other oncology services dealing with the increasing demands of an aging population in a time of increasingly limited resources.

CORBA on Mobile Devices

2007 ◽  
pp. 160-164
Author(s):  
M. Aleksy
Keyword(s):  
Mobile Devices ◽  
Limited Resources ◽  
Central Problem ◽  
Research Groups ◽  
The Past ◽  
Memory Footprint ◽  
Major Bottleneck

While CORBA has been very successful in the domain of enterprise computing, its adoption for mobile devices is obstructed by a central problem: the limited resources of such devices. If standard-compliant CORBA-based applications are to be executed on mobile devices, storage requirements, for example, represent a major bottleneck. But for all that, several research groups have made an effort over the past few years to establish the CORBA standard in the domain of mobile devices. The existing approaches can be divided into three categories:1. approaches that are restricted in the sense that they use an implementation of the IIOP protocol only,2. approaches that build on the minimum CORBA specification, and3. approaches that rely on other ways to reduce the memory footprint of a CORBA implementation. In the following sections of this chapter, these approaches will be discussed in detail.

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