5,287 research outputs found
Different landscape factors explain establishment and persistence of river red gum (Eucalyptus camaldulensis) in agricultural landscapes of southeast Queensland
Riparian and floodplain ecosystems in production landscapes are considerably degraded and under continued pressure from surrounding land use. However, little is known about how remnant ecosystems respond to land use and hydrological factors in small non-riverine wetlands. River red gum (Eucalyptus camaldulensis) is a dominant tree species within these scattered remnants, which provides critical ecological functions for the remaining biodiversity. In this study, we investigated how different life stages of E. camaldulensis responded to land use and hydrological variables in the Condamine catchment of south east Queensland. We used logistic regression to develop models for different life stages of E. camaldulensis in two regions with differing land use intensity histories. Broad regional differences and land use practices at smaller scales best explained differences in E. camaldulensis occurrence for younger life stages, while hydrology (groundwater and connectivity to rivers) and land use practices (dryland agriculture and grazing) best explained differences in older life stages. The results indicate that different factors are important in determining the establishment and persistence of E. camaldulensis and that land use practices at the regional scale are key factors in determining the establishment and potential future persistence of E. camaldulensis in floodplain wetlands
If and to What Extent Does Organizational Learning Culture Predict Turnover Intentions of Telecommuting Call Center Agents?
This study focuses on measuring the relationship between organizational learning culture (OLC) and turnover intentions of telecommuting call center agents. Although many studies involve the call center industry from different perspectives, the literature is scant in studies that have assessed the relationship between OLC and turnover intent in telecommuting call center agents. Call centers exist in almost every organization worldwide. Organizations have centralized their customer service process through computerbased technologies allowing call center agents to work from home. In addition, in the post-COVID-19 era, telecommuting has become a permanent option for many call center employees. Indeed, in the call center industry, telecommuting has become an essential part of the business strategy that seeks to attract new and maintain current employees. In the call center industry, learning is a factor that influences job satisfaction and turnover intentions. Specifically, OLC increases job satisfaction and performance in telecommuting call center agents, influencing employees’ turnover intentions. The study’s findings indicate that OLC is a needed factor that helps lower turnover intentions of telecommuting call center agents in the United States
Understanding Leadership for Adaptive Change in Catholic Schools: A Complexity Perspective
In an era of decline and crisis, Catholic school leaders have been encouraged to find innovative ways to enhance a school’s operational vitality. Yet to this point, most research on educational change in Catholic schools has focused on the technical tasks school principals can take to “save” individual schools. In this article, we apply a complexity perspective to educational change leadership in Catholic education: leadership for adaptive change. Based on a new empirical analysis of the professional experiences of two Catholic school principals working at four different parish schools, we demonstrate in this article how leadership for adaptive change can operate in Catholic elementary parish schools and assess whether and how the attributes of complex adaptive schools were present in these four elementary schools. We also highlight the organizational and social conditions these two principals confronted that both undermined and promoted their ability to lead for adaptive change at these four schools. Ultimately, we suggest in this article the utility of using a “complex adaptive” approach to understanding change leadership in Catholic elementary schools as opposed to “technically rational” approaches commonly found in contemporary Catholic school leadership research
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Data Assimilation in Models with Convective Adjustment
Practical hydrostatic ocean models are often restricted to statically stable configurations by the use of a convective adjustment. A common way to do this is to assign an infinite boat conductivity to the water at a given level if the water column should become statically unstable. This is implemented in the form of a switch. When a statically unstable configuration is detected, it is immediately replaced with a statically stable one in which heat is conserved. In this approach, the model is no longer governed by a smooth set of equations, and usual techniques of variational data assimilation must be modified. In this note, a simple one-dimensional diffusive model is presented. Despite its simplicity, this model captures the essential behavior of the convective adjustment scheme in a widely used ocean general circulation model. Since this simple model can be derived from the more complex general circulation model, it then follows that many of the properties of the constrained system can be observed in this very simple scalar ordinary differential equation with a constraint on the solution. Techniques from the theory of optimal control are used to find solutions of a simple formulation of the variational data assimilation problem in this simple case. The optimal solution involves the solution of a nonlinear problem, even when the unconstrained dynamics are linear. In cases with discontinuous dynamics, one cannot define the adjoint of the linearized system in a straightforward manner. The very simplest variational formulation is shown to have nonunique stationary points and undesirable physical consequences. Modifications that lead to better behaved calculations and more meaningful solutions are presented. Whereas it is likely that the underlying principles from control theory are applicable to practical ocean models, the technique used to solve the simple problem may be applicable only to steady problems. Derivation of suitable techniques for initial value problems will involve a major research effort
An X-Ray View of the Jet-Cycle in the Radio Loud AGN 3C120
We present a study of the central engine in the broad-line radio galaxy 3C120
using a multi-epoch analysis of a deep XMM-Newton observation and two deep
Suzaku pointings (in 2012). In order to place our spectral data into the
context of the disk-disruption/jet-ejection cycles displayed by this object, we
monitor the source in the UV/X-ray bands, and in the radio band. We find three
statistically acceptable spectral models, a disk-reflection model, a jet-model
and a jet+disk model. Despite being good descriptions of the data, the
disk-reflection model violates the radio constraints on the inclination, and
the jet-model has a fine-tuning problem, requiring a jet contribution exceeding
that expected. Thus, we argue for a composite jet+disk model. Within the
context of this model, we verify the basic predictions of the jet-cycle
paradigm, finding a truncated/refilling disk during the Suzaku observations and
a complete disk extending down to the innermost stable circular orbit (ISCO)
during the XMM-Newton observation. The idea of a refilling disk is further
supported by the detection of the ejection of a new jet knot approximately one
month after the Suzaku pointings. We also discover a step-like event in one of
the Suzaku pointings in which the soft band lags the hard band. We suggest that
we are witnessing the propagation of a disturbance from the disk into the jet
on a timescale set by the magnetic field.Comment: 14 pages, 10 figures, accepted for publication in Ap
Information/knowledge design in contextual hypermedia systems
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 1998.Includes bibliographical references (leaves 51-55).As we begin to comprehend the ways we interact with the data/information/knowledge structures which construct our individual perception of reality, we see a shift from the dyadic Cartesian method of reading our environment, to a triadic, or Systems View, which accounts for individual perceptual readings and individual realities. This shift in thinking relates that we are dynamic, self-organizing, complex systems which form an individual perception of our environment based on the relationships we identify between ourselves and the interrelated systems of data/information around us. Recognizing this shift, the research project associated with this thesis, utilizes interactive digital multimedia, or hypermedia, in the design of a set of tools with which to identify and illustrate these interrelated systems. It is the author's belief that once identified, these dynamic relationships will provide an ideal source of user-defined navigation of the group of interrelated objects. The dynamic qualities of hypermedia, which provide the author different modes of linking information of many different data types to one another, making it an ideal venue for the illustration and navigation of systemic relationships. Employing two and three dimensional methods of visual and spatial representation, integrated with in various combinations of graphic organizational models, the product of th is thesis will provide the user an information-rich environment in which to identify and navigate the associative relationships found amongst a group of physical objects, in th is case furniture of modern design. The thesis also looks ahead to speculate on the impact of emerging technologies such as Augmented Reality, Virtual Reality, and Tangible User Interfaces, on the design of information knowledge "spaces". The author will propose a future implementation of these technologies in relation to the current subject of illustration.by Andrew F. Miller.S.M
Applications of Improvements to the Pythagorean Won-Loss Expectation in Optimizing Rosters
Bill James' Pythagorean formula has for decades done an excellent job
estimating a baseball team's winning percentage from very little data: if the
average runs scored and allowed are denoted respectively by and
, there is some such that the winning percentage is
approximately . One
important consequence is to determine the value of different players to the
team, as it allows us to estimate how many more wins we would have given a
fixed increase in run production. We summarize earlier work on the subject, and
extend the earlier theoretical model of Miller (who estimated the run
distributions as arising from independent Weibull distributions with the same
shape parameter; this has been observed to describe the observed run data
well). We now model runs scored and allowed as being drawn from independent
Weibull distributions where the shape parameter is not necessarily the same,
and then use the Method of Moments to solve a system of four equations in four
unknowns. Doing so yields a predicted winning percentage that is consistently
better than earlier models over the last 30 MLB seasons (1994 to 2023). This
comes at a small cost as we no longer have a closed form expression but must
evaluate a two-dimensional integral of two Weibull distributions and
numerically estimate the solutions to the system of equations; as these are
trivial to do with simple computational programs it is well worth adopting this
framework and avoiding the issues of implementing the Method of Least Squares
or the Method of Maximum Likelihood
Seed size and its rate of evolution correlate with species diversification across angiosperms
Species diversity varies greatly across the different taxonomic groups that comprise the Tree of Life (ToL). This imbalance is particularly conspicuous within angiosperms, but is largely unexplained. Seed mass is one trait that may help clarify why some lineages diversify more than others because it confers adaptation to different environments, which can subsequently influence speciation and extinction. The rate at which seed mass changes across the angiosperm phylogeny may also be linked to diversification by increasing reproductive isolation and allowing access to novel ecological niches. However, the magnitude and direction of the association between seed mass and diversification has not been assessed across the angiosperm phylogeny. Here, we show that absolute seed size and the rate of change in seed size are both associated with variation in diversification rates. Based on the largest available angiosperm phylogenetic tree, we found that smaller-seeded plants had higher rates of diversification, possibly due to improved colonisation potential. The rate of phenotypic change in seed size was also strongly positively correlated with speciation rates, providing rare, large-scale evidence that rapid morphological change is associated with species divergence. Our study now reveals that variation in morphological traits and, importantly, the rate at which they evolve can contribute to explaining the extremely uneven distribution of diversity across the ToL
Critical Rhetoric and Collaboration: Missing Principle #9 and ProfsDoPop.com
As part of this Special Section on critical rhetoric, this article examines the role of collaboration in the future of critical rhetoric. Building on McKerrow’s original eight principles of praxis, the authors advocate for a missing ninth principle that reflects the need for critical rhetoric to be a shared venture across both individual projects and larger discourses. As an example of this type of work, they provide ProfsDoPop.com, an academic, online blog designed to bring academic sensibilities and concepts to popular audiences through the critique of popular culture
Modification of β-Sheet Forming Peptide Hydrophobic Face: Effect on Self-Assembly and Gelation
β-Sheet forming peptides have attracted significant interest for the design of hydrogels for biomedical applications. One of the main challenges is the control and understanding of the correlations between peptide molecular structure, the morphology, and topology of the fiber and network formed as well as the macroscopic properties of the hydrogel obtained. In this work, we have investigated the effect that functionalizing these peptides through their hydrophobic face has on their self-assembly and gelation. Our results show that the modification of the hydrophobic face results in a partial loss of the extended β-sheet conformation of the peptide and a significant change in fiber morphology from straight to kinked. As a consequence, the ability of these fibers to associate along their length and form large bundles is reduced. These structural changes (fiber structure and network topology) significantly affect the mechanical properties of the hydrogels (shear modulus and elasticity)
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