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"Deller, J."
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Bilobate comet morphology and internal structure controlled by shear deformation
Bilobate comets—small icy bodies with two distinct lobes—are a common configuration among comets, but the factors shaping these bodies are largely unknown. Cometary nuclei, the solid centres of comets, erode by ice sublimation when they are sufficiently close to the Sun, but the importance of a comet’s internal structure on its erosion is unclear. Here we present three-dimensional analyses of images from the Rosetta mission to illuminate the process that shaped the Jupiter-family bilobate comet 67P/Churyumov–Gerasimenko over billions of years. We show that the comet’s surface and interior exhibit shear-fracture and fault networks, on spatial scales of tens to hundreds of metres. Fractures propagate up to 500 m below the surface through a mechanically homogeneous material. Through fracture network analysis and stress modelling, we show that shear deformation generates fracture networks that control mechanical surface erosion, particularly in the strongly marked neck trough of 67P/Churyumov–Gerasimenko, exposing its interior. We conclude that shear deformation shapes and structures the surface and interior of bilobate comets, particularly in the outer Solar System where water ice sublimation is negligible.The shape and internal structure of bilobate comet 67P is controlled by shear deformation inducing mechanically driven erosion along shear fracture networks, according to a 3D analysis of images from the Rosetta mission.
Journal Article
Road safety community partnership in Queensland, Australia
Acknowledging the shortfall in addressing road safety, in May 2007 a coordinated approach to road safety commenced in Moreton Bay, Queensland, Australia. A multi-agency approach led to the development of a road safety partnership project to reduce road trauma at the local government ‘grass roots’ level through infrastructure and behaviour changes initiatives. This paper traces the journey taken to introduce a road safety officer into the Moreton Bay Regional Council along with developing appropriate road trauma reduction strategies and actions across all travel modes at the local government level. The scheme has already won several awards. In April 2009, it was announced that the scheme would be introduced across Queensland through the regional road groups in the form of a road safety community partnership programme. With the development of a simple web-based template approach to developing road safety strategy and actions plans along with a road safety reference group providing peer support it is hoped that this approach is the dawn of a greater road safety focus for Queensland addressing the global issue of road trauma through local governments.
Journal Article
Organizational justice and managerial commitment in corporate mergers
Purpose - The purpose of this paper is to investigate whether perceptions of distributive, procedural and interactional justice can explain the frequently reported low organizational commitment of managers in corporate mergers. Specifically, it aims to examine whether each of the justice dimensions is significantly and uniquely related to affective commitment, which of the justice dimensions has the strongest relationship with the criterion, and whether instrumental evaluations or trust might function as a mediator.Design methodology approach - A total of 128 managers from 37 companies completed a questionnaire. They had been involved in domestic or European mergers or acquisitions, which varied in the application of fairness rules.Findings - Although each fairness dimension correlated positively with affective commitment, only interactional justice showed a unique relationship with it. Results indicate that both instrumental evaluations and trust can function as a mediator.Research limitations implications - Because of the cross-sectional design, conclusions about the causal order of the variables cannot be drawn.Practical implications - The authors recommend that top managers should pay extra attention to timely, candid and specific internal communication with thorough and reasonable explanation of decisions, as well as the respectful treatment of managers. Moreover, the results indicate that managers reacted positively to fairness because it conveys positive relational signals, and because one can gain personal advantages through fair outcomes and processes.Originality value - The organizational justice approach has not yet been applied, to the authors' knowledge, in quantitative field studies of mergers. Furthermore, this paper offers a contribution to the literature on fairness heuristic theory.
Journal Article
Rosetta's comet 67P/Churyumov-Gerasimenko sheds its dusty mantle to reveal its icy nature
The Rosetta spacecraft has investigated comet 67P/Churyumov-Gerasimenko from large heliocentric distances to its perihelion passage and beyond. We trace the seasonal and diurnal evolution of the colors of the 67P nucleus, finding changes driven by sublimation and recondensation of water ice. The whole nucleus became relatively bluer near perihelion, as increasing activity removed the surface dust, implying that water ice is widespread underneath the surface. We identified large (1500 square meters) ice-rich patches appearing and then vanishing in about 10 days, indicating small-scale heterogeneities on the nucleus. Thin frosts sublimating in a few minutes are observed close to receding shadows, and rapid variations in color are seen on extended areas close to the terminator. These cyclic processes are widespread and lead to continuously, slightly varying surface properties.
Journal Article
Surface changes on comet 67P/Churyumov-Gerasimenko suggest a more active past
The Rosetta spacecraft spent ~2 years orbiting comet 67P/Churyumov-Gerasimenko, most of it at distances that allowed surface characterization and monitoring at submeter scales. From December 2014 to June 2016, numerous localized changes were observed, which we attribute to cometary-specific weathering, erosion, and transient events driven by exposure to sunlight and other processes. While the localized changes suggest compositional or physical heterogeneity, their scale has not resulted in substantial alterations to the comet’s landscape. This suggests that most of the major landforms were created early in the comet’s current orbital configuration. They may even date from earlier if the comet had a larger volatile inventory, particularly of CO or CO₂ ices, or contained amorphous ice, which could have triggered activity at greater distances from the Sun.
Journal Article
EFFECTS OF JOB RESOURCES ON WORK ABILITY IN HIGH QUALIFIED MANAGEMENT POSITIONS
The prolongation of work lives could attenuate the challenges of the demographic change. In order to maintain and improve the productiveness of the workforce, work ability is gaining increasing importance in both, research and practice. On average, age leads to a decline in work ability, and, consequently, work force participation. However, age also leads to an increase in work ability score variance, indicating the presence of moderating effects with an impact on the relationship of age and work ability. In line with the Job-Demands Resources Model and the Conservation of Resources Theory, we evaluated direct and possible moderating effects of job resources, i.e., characteristics of the supervisor, discrimination, respect, and autonomy on the relationship between age and work ability. Data of 1,093 managers of the chemical industry in Germany were used. Managers not only are subject to factors of their work environment, but are also important role-models for their direct reports, and are therefore of twofold interest. In hierarchical regression analyses, we found direct impact on work ability for all job resources. Additionally, the analyses indicated moderating effects of advancement discrimination, control of work, and skill usage on the age-related decline of work ability. The findings are discussed regarding relevant literature. Our research can help employers facing demographic challenges to effectively employ interventions to improve health and work ability of their aging work forces, especially when mere individual-focusing interventions fail to do so.
Journal Article
INTERGENERATIONAL KNOWLEDGE TRANSFER: ANTECEDENTS OF A DYADIC PROCESS
The aging of skilled workforces is a major challenge for organizations. In light of the massive wave of retirements of members of the baby boomer generation, the retention of valuable organizational knowledge from older and retiring workers has been identified as an urgent need. In this study, we integrate socio-emotional selectivity theory and the theory of psychosocial development to explain how individual characteristics of older and younger employees influence the intergenerational knowledge transfer process. We propose a moderated mediation model: First, we hypothesize that older employees’ focus on generativity and younger employees’ focus on extrinsic growth values predict their knowledge sharing and receiving behavior. Second, we propose that the effects of work values on knowledge sharing and receiving behavior are mediated by employees’ willingness to engage in intergenerational knowledge transfer. Third, we argue that the indirect effects of work values on knowledge sharing and receiving behavior are moderated by age-diversity climate, such that if age-diversity climate is more pronounced, the proposed relationships are stronger. We collected multi-source, time-lagged data from 80 intergenerational knowledge transfer dyads (i.e., older and younger employees), who were based in four German companies that operate in the financial services industry. We found support for most of our propositions. The study contributes to research on aging workforces and intergenerational interactions at the workplace by showing that the individual characteristics of both older and younger employees influence knowledge retention. Further, the study shows that contextual variables can influence intergenerational knowledge transfer processes.
Journal Article
Set-membership identification and filtering for signal processing applications
Optimal bounding ellipsoid (OBE) algorithms comprise a class of novel recursive identification methods for affine-in-parameters system and signal models. OBE algorithms exploit a priori knowledge of bounds on model disturbances to derive a monotonically nonincreasing set of solutions that are feasible in light of the observations and the model structure. In turn, these sets admit criteria for ascertaining the information content of incoming observations, obviating the expense of updating when data are redundant. Relative to classical recursive methods for this task, OBE algorithms are efficient, robust, and exhibit remarkable tracking ability, rendering them particularly attractive for realtime signal processing and control applications. After placing the OBE algorithms in the hierarchy of the broader set-membership identification methods, this article introduces the underlying set-theoretic concepts, compares and contrasts the various published OBE algorithms including the motivation for each development, then concludes with some illustrations of OBE algorithm performance. More recent work on the use of OBE processing infiltering tasks is also included in the discussion. The paper is a survey of a broad and evolving topic, and extensive references to further information are included.[PUBLICATION ABSTRACT]
Journal Article
The pristine interior of comet 67P revealed by the combined Aswan outburst and cliff collapse
Outbursts occur commonly on comets
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with different frequencies and scales
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,
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. Despite multiple observations suggesting various triggering processes
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,
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, the driving mechanism of such outbursts is still poorly understood. Landslides have been invoked
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to explain some outbursts on comet 103P/Hartley 2, although the process required a pre-existing dust layer on the verge of failure. The Rosetta mission observed several outbursts from its target comet 67P/Churyumov–Gerasimenko, which were attributed to dust generated by the crumbling of materials from collapsing cliffs
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,
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. However, none of the aforementioned works included definitive evidence that landslides occur on comets. Amongst the many features observed by Rosetta on the nucleus of the comet, one peculiar fracture, 70 m long and 1 m wide, was identified on images obtained in September 2014 at the edge of a cliff named Aswan
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. On 10 July 2015, the Rosetta Navigation Camera captured a large plume of dust that could be traced back to an area encompassing the Aswan escarpment
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. Five days later, the OSIRIS camera observed a fresh, sharp and bright edge on the Aswan cliff. Here we report the first unambiguous link between an outburst and a cliff collapse on a comet. We establish a new dust-plume formation mechanism that does not necessarily require the breakup of pressurized crust or the presence of supervolatile material, as suggested by previous studies
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. Moreover, the collapse revealed the fresh icy interior of the comet, which is characterized by an albedo >0.4, and provided the opportunity to study how the crumbling wall settled down to form a new talus.
A bright outburst of activity from the nucleus of comet 67P, observed by Rosetta in July 2015, is traced back to a cliff that partially collapsed at the same time as the outburst, establishing a link between the two events. The collapse has also exposed the fresh ice present under the surface.
Journal Article