scholarly journals Fundamental Flaws with the Fundamental Niche

2019 ◽  
Vol 59 (4) ◽  
pp. 1038-1048 ◽  
Author(s):  
Michael J Angilletta ◽  
Michael W Sears ◽  
Ofir Levy ◽  
Jacob P Youngblood ◽  
John M VandenBrooks
Keyword(s):  
Spatial Configuration ◽  
Life Stage ◽  
Spatiotemporal Variation ◽  
Mechanistic Models ◽  
Ecological Research ◽  
Ample Evidence ◽  
Abiotic Conditions ◽  
Fundamental Niche ◽  
And Performance ◽  
Stress Influence

Abstract For more than 70 years, Hutchinson’s concept of the fundamental niche has guided ecological research. Hutchinson envisioned the niche as a multidimensional hypervolume relating the fitness of an organism to relevant environmental factors. Here, we challenge the utility of the concept to modern ecologists, based on its inability to account for environmental variation and phenotypic plasticity. We have ample evidence that the frequency, duration, and sequence of abiotic stress influence the survivorship and performance of organisms. Recent work shows that organisms also respond to the spatial configuration of abiotic conditions. Spatiotemporal variation of the environment interacts with the genotype to generate a unique phenotype at each life stage. These dynamics cannot be captured adequately by a multidimensional hypervolume. Therefore, we recommend that ecologists abandon the niche as a tool for predicting the persistence of species and embrace mechanistic models of population growth that incorporate spatiotemporal dynamics.

Rheology of Adhesion

1972 ◽  
Vol 45 (6) ◽  
pp. 1604-1622 ◽  
Author(s):  
D. H. Kaelble
Keyword(s):  
Polymer Composites ◽  
Three Dimensional ◽  
Polymeric Materials ◽  
Intermolecular Forces ◽  
Adhesive Joints ◽  
Polymer Chains ◽  
System Response ◽  
Ample Evidence ◽  
Volume State ◽  
And Performance

Abstract This discussion has outlined a series of considerations which begin with engineering definitions of system response of adhesive joints and end with propositions involving molecular interactions at interfaces. Connecting these extreme aspects of the argument is the central subject of the micromechanics of bonding and fracture. Cavitation theory, as simply described by Equations (6a) and (7), illustrates the scale of microresponse in which both the thermodynamic and rheological aspects of adhesion phenomena achieve a parity when applied to cavities of radius r=0.1 to 10 μ. The discussion of the micromechanics of polymer fracture provides ample evidence that pure materials, polymer composites, and adhesive joints, need to be described in terms of their microdefects. The several mathematical models for crack propagation which are imposed upon fracture mechanics data tend to oversimplify the visualization of the true micromechanisms of fracture. The fuller development of micromechanics theory and experimental analysis promises to be an important area of current developments in the better understanding of macroscopic response of filled systems, fiber reinforced composites, and adhesively bonded structures. Recent developments in the several theories of intermolecular forces and the physical chemistry of bonding provide new impetus to the chemist to design optimized polymeric materials with finely adjusted balances of surface and bulk properties. The fuller visualization of adsorption-interdiffusion bonding as a process involving both the two-dimensional interface and the three-dimensional interphase defines bonding as both a thermodynamical and a rheological process. The microstages of bond formation are somewhat the reverse of the stages of microfracture listed earlier. The microdefects that commonly exist in polymeric materials and polymer composites tend to indicate that the viscoelastic constraints typical of polymer chains and networks play an important role in preventing equilibrium bonding in the simple thermodynamic sense as expressed by idealized liquid—liquid or liquid—solid interactions. The current development and application of a refined thermodynamical and rheological argument to both bonding and fracture processes stands as a central issue in directly correlating the molecular criteria of adhesion and performance of bonded systems. Any of the simple mathematical relations introduced in this discussion may be expressed with greater detail and precision by incorporating detailed statements concerning chemical composition, macromolecular structure, and free volume state of the polymeric adhesive.

To Continue or not to Continue? Drivers of Recurrent Partnering in Temporary Organizations

2016 ◽  
Vol 37 (12) ◽  
pp. 1861-1895 ◽  
Author(s):  
Mark Ebers ◽  
Indre Maurer
Keyword(s):  
Experiential Learning ◽  
Empirical Evidence ◽  
Opportunity Cost ◽  
Performance Outcomes ◽  
Ample Evidence ◽  
Temporary Organizations ◽  
Project Organizations ◽  
And Performance ◽  
Project Partner ◽  
Forward Looking

While research has provided ample evidence that temporal (dis-)continuity in partnering is highly consequential for the governance and performance outcomes of temporary organizations, we know much less about the conditions that drive the members of temporary organizations to engage in recurrent partnering. Focusing on project organizations, the present research offers theoretical arguments and related empirical evidence that illuminate when and why project-leading organizations expect to continue collaboration with the same project partner in future projects. Specifically, we show that expectations of recurrent collaboration are a function of backward-looking experiential learning and forward-looking opportunity cost assessments. Our findings contribute to better understanding of temporality in temporary organizations by uncovering a set of factors conducive to explaining when and why the same partners engage in temporary sequences of projects.

Impacts of Active Learning on Student Outcomes in Large-Lecture Biology Courses

2016 ◽  
Vol 78 (8) ◽  
pp. 651-655 ◽  
Author(s):  
Kristy L. Daniel
Keyword(s):  
Active Learning ◽  
Student Performance ◽  
Learning Strategies ◽  
Group Discussion ◽  
Learning Gains ◽  
Ample Evidence ◽  
Large Lecture ◽  
Biology Courses ◽  
And Performance ◽  
Collaborative Activities

Learning theorists have provided ample evidence supporting the use of active, student-centered, social learning environments. However, little action has been taken within U.S. university curricula to transform lecture courses so that they include such teaching methods. By adding cooperative and collaborative activities into large-lecture, introductory biology courses, I was able to measure the impacts of such active-learning strategies on student attendance and performance. I gathered data from two investigations involving 378 undergraduates from paired sections of biology, one section using active-learning activities and one not. In the first investigation, I used a mixed-methods approach to measure the effects of a cooperative pre-exam group discussion on student performance, confidence, and anxiety. In the second investigation, I used a quantitative approach to measure the effects on course attendance and performance of using scenario-based collaborative activities regularly throughout a semester. Students who engaged in cooperative pre-exam discussion did not show significant individual learning gains but did show an increase in confidence and a decrease in anxiety. Students who engaged in scenario-based collaborative activities showed significantly higher learning gains and course attendance. The identified gains are promising for course reform.

Review of Methods for Battery Life Modeling and Their Applications

2010 ◽  
Vol 29-32 ◽  
pp. 2392-2397 ◽  
Author(s):  
Wei Jun Gu ◽  
Ze Chang Sun ◽  
Xue Zhe Wei ◽  
Hai Feng Dai
Keyword(s):  
Life Prediction ◽  
Life Stage ◽  
Research Work ◽  
Battery Life ◽  
Battery Management System ◽  
Battery Management ◽  
Application Range ◽  
True State ◽  
Life Model ◽  
And Performance

Battery Management System (BMS) mainly focused on the estimation of State-of-Charge (SOC) previously. However, the single SOC could not reflect the true state of battery. Life prediction and performance state estimation becomes an increasingly important issue in each battery life stage. A practical and accurate battery life model is their basis. Much research work has been done in recent years to improve the accuracy and application range of battery life model. This paper introduces commonly used battery life modeling methods and summarized the characteristics of each model and their common applications, and the emphasis for future study is proposed as well.

scholarly journals Dewatering of Cellulose Nanofibrils using Ultrasound

2021 ◽  
Author(s):  
Udita Ringania ◽  
Joseph Harrison ◽  
Robert J. Moon ◽  
M. Saad Bhamla
Keyword(s):  
Spatial Configuration ◽  
Low Cost ◽  
Cellulose Nanofibrils ◽  
Microscopic Analysis ◽  
Drying Methods ◽  
Contact Mode ◽  
Significant Difference ◽  
Flow Configurations ◽  
And Performance ◽  
Cellulose Nanomaterials

Abstract Although cellulose nanomaterials have promising properties and performance in a wide application space, one hinderance to their wide scale industrial application has been associated with their economics of dewatering and drying and the ability to redisperse them back into suspension without introducing agglomerates or lose of yield. The present work investigates the dewatering of aqueous suspensions of cellulose nanofibrils (CNF) using ultrasound as a potentially low-cost, non-thermal, and scalable alternative to traditional heat-based drying methods such as spray drying. Specifically, we use vibrating mesh transducers to develop a direct-contact mode ultrasonic dewatering platform to remove water from CNF suspensions in a continuous manner. We demonstrate that the degree of dewatering is modulated by the number of transducers, their spatial configuration, and the flow rate of the CNF suspension. Water removal of up to 72 wt.% is achieved, corresponding to a final CNF concentration of 11 wt.% in 30 minutes using a twotransducer configuration. To evaluate the redispersibility of the dewatered CNF material, we use a microscopic analysis to quantify the morphology of the redispersed CNF suspension. By developing a custom software pipeline to automate image analysis, we compare the histograms of the dimensions (length, width) of the redispersed dewatered fibrils with the original CNF samples and observe no significant difference, suggesting that no agglomeration is induced due to ultrasonic dewatering. We estimate that this ultrasound dewatering technique is also energyefficient, consuming up to 36% less energy than the enthalpy of evaporation per kilogram of water. Together with the inexpensive cost of transducers (<$1), the potential for scaling up in parallel flow configurations, and excellent redispersion of the dewatered CNF, our work offers a proof-ofconcept of a sustainable CNF dewatering system, that addresses the shortcomings of existing techniques.

scholarly journals Exploring the Topological Characteristics of Complex Public Transportation Networks: Focus on Variations in Both Single and Integrated Systems in the Seoul Metropolitan Area

2019 ◽  
Vol 11 (19) ◽  
pp. 5404 ◽  
Author(s):  
Jungyeol Hong ◽  
Reuben Tamakloe ◽  
Soobeom Lee ◽  
Dongjoo Park
Keyword(s):  
Public Transportation ◽  
Spatial Configuration ◽  
Transportation Networks ◽  
Transportation Network ◽  
Spatial Accessibility ◽  
Structural Defects ◽  
Centrality Measures ◽  
Integrated Networks ◽  
Public Transportation Network ◽  
And Performance

Many cities have integrated their public transportation modes to provide increased accessibility and reduced commute times. However, current transport network topology studies have focused on unimodal networks. Therefore, it is of significant interest for policymakers to examine the topology of integrated public transportation networks and to assess strategies for improving them. The objective of this study was to discuss a comprehensive analysis of an integrated public transportation network using graph theory, compare its characteristics to unimodal networks, and draw insights for improving their performance. Results demonstrate pertinent information concerning the structural composition of the Seoul Metropolitan Area’s (SMA) public transportation network. Despite the integration, the spatial configuration of the network was found to have low fault tolerance. However, the highly agglomerated community structure validated the robustness of integrated networks. Network centrality measures confirmed that integration improves connectivity and spatial accessibility to suburbs within the city. The study found that the SMA’s current public transportation network possesses structural defects that need to be addressed to improve its resilience and performance. Based on the outcomes of this study, the strategic creation or relocation of stations, and the construction of more links, is imperative for the enhancement of mobility.

Transmission Scanning Electron Microscopy and Energy Analysis with the Siemens ELMISKOP 101

1972 ◽  
Vol 30 ◽  
pp. 450-451
Author(s):  
H. M. Thieringer
Keyword(s):  
Objective Lens ◽  
Transmission Microscopy ◽  
Image Recording ◽  
Mode Of Operation ◽  
Scanning Transmission ◽  
Electron Microscopes ◽  
And Performance ◽  
Convergent Beam ◽  
Ray Path ◽  
Beam Diffraction

It has repeatedly been show that with conventional electron microscopes very fine electron probes can be produced, therefore allowing various micro-techniques such as micro recording, X-ray microanalysis and convergent beam diffraction. In this paper the function and performance of an SIEMENS ELMISKOP 101 used as a scanning transmission microscope (STEM) is described. This mode of operation has some advantages over the conventional transmission microscopy (CTEM) especially for the observation of thick specimen, in spite of somewhat longer image recording times.Fig.1 shows schematically the ray path and the additional electronics of an ELMISKOP 101 working as a STEM. With a point-cathode, and using condensor I and the objective lens as a demagnifying system, an electron probe with a half-width ob about 25 Å and a typical current of 5.10-11 amp at 100 kV can be obtained in the back focal plane of the objective lens.

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