Degeneracy and networked buffering: principles for supporting emergent evolvability in agile manufacturing systems

This article introduces new principles for improving upon the design and implementation of agile manufacturing and assembly systems. It focuses particularly on challenges that arise when dealing with novel conditions and the associated requirements of system evolvability, e.g. seamless reconfigurability to cope with changing production orders, robustness to failures and disturbances, and modifiable user-centric interfaces. Because novelty in manufacturing or the marketplace is only predictable to a limited degree, the flexible mechanisms that will permit a system to adequately respond to novelty cannot be entirely pre-specified. As a solution to this challenge, we propose how evolvability can become a pervasive property of the assembly system that, while constrained by the system??s historical development and domain-specific requirements, can emerge and re-emerge without foresight or planning. We first describe an important mechanism by which biological systems can cope with uncertainty through properties described as degeneracy and networked buffering. We discuss what degeneracy means, how it supports a system facing unexpected challenges, and we review evidence from simulations using evolutionary algorithms that support some of our conjectures in models with similarities to several assembly system contexts. Finally, we discuss potential design strategies for encouraging emergent changeability in assembly systems. We also discuss practical challenges to the realization of these concepts within a systems engineering context, especially issues related to system transparency, design costs, and efficiency. We discuss how some of these difficulties can be overcome while also elaborating on those factors that are likely to limit the applicability of these principles.     

Transformations of Planning Rationales: Changing Spaces for Governance in Recent Dutch National Planning

Dutch national planning has acquired an international reputation because it provides strong planning guidance while simultaneously being responsive to the particular spatial and political circumstances of different regions and areas. Spatial concepts, like the Randstad, are important vehicles for sustaining this approach. Such concepts incorporate select spatial planning rationales that justify operational decisions. Concepts can, however, also be ambiguous, and this can allow for different interpretations and deliberations about how guidance should take effect in different situations. In this paper we assess the degree of ambiguity contained in concepts outlined in Dutch national plans between 1988 and 2012. By focusing on the dimensions of spatial concepts, and the room for interpretation these create, we demonstrate how concepts were modified to accommodate a shifting appreciation of deliberation and, as a result, collaboration and governance. On a theoretical level, we propose a method that analyses in detail the ambiguity (“fuzzyness” or “softness”) of spatial concepts. We argue that such sophisticated understandings contribute to explaining the variety of governance responses that these geographies produce in practice. On an empirical level we seek to increase understanding of change in recent Dutch national planning.     

Design, fabrication, and characterization of diffraction gratings for neutron phase contrast imaging

We have developed a neutron phase contrast imaging method based on a grating interferometer setup. The principal constituents are two absorption gratings made of gadolinium and a phase modulating grating made of silicon. The design parameters of the setup, such as periodicity, structure heights of the gratings, and the distances between the gratings, are calculated. The fabrication of each grating is described in detail. The produced diffraction gratings were finally characterized within the setup, by locally evaluating the produced contrast (visibility) in each detector pixel, resulting in a visibility map over the whole grating size. An averaged value of 23% is achieved.     

Highly absorbing gadolinium test device to characterize the performance of neutron imaging detector systems

We report on the fabrication and application of a novel neutron imaging test device made of gadolinium. It is designed for a real time evaluation of the spatial resolution, resolution direction, and distortions of a neutron imaging detector system. Measurements of the spatial resolution of (6)LiF doped ZnS scintillator screens with different thicknesses and of imaging plates were performed. The obtained results are in good agreement with comparison measurements using the standard knife edge detection method.     

Computer simulation of ESD from voluminous objects compared totransient fields of humans

Computer simulation of electrostatic discharge (ESD) for simplified objects is described and compared to measured transient fields of human/metal ESD. The simulation algorithm uses the method of moments in time domain, coupled with nonlinear arc resistance model. Transient currents and fields are analyzed from the electromagnetic compatibility (EMC) point of view. Validation of the numerical simulation is done by comparison to experimental data. The simulated structure models the human/metal ESD in its peak current and field values and their derivatives reasonably well     

Lack of effects on heart rate and blood pressure inketamine-anesthetized rats briefly exposed to ultra-widebandelectromagnetic pulses

Fourteen Sprague-Dawley rats were exposed to pulses produced by a Bournlea ultra-wideband (UWB) pulse generator (rise time, 318-337 ps; maximum E field, 19-21 kV/m). Exposures at a repetition frequency of 1 kHz for 0.5 s or to repetitive pulse trains (2-s exposure periods alternating with 2 s of no exposure, for a total of 2 min) resulted in no significant changes in heart rate or mean arterial blood pressure. These results suggest that acute whole-body exposure to UWB pulses does not have a detrimental effect on the cardiovascular system     

Long-term, low-level exposure of mice prone to mammary tumors to 435 MHz radiofrequency radiation

Six hundred and thirty four interviews of injecting drug users were performed between 1992 and 1994 as part of a study of injecting drug use and HIV prevalence in Edinburgh, Scotland. Amphetamine was injected by more subjects (44%) than any other drug. Preference for injection as the route of administration of amphetamine increased over the period despite no change in the popularity of the drug generally. Simultaneously, heroin use and injection declined. Analyses indicated that amphetamine injectors comprised two distinct sub-groups. The majority were polydrug injectors who injected frequently, had a longer injecting history and were more likely to share injection equipment. About one-fifth were stimulant-only injectors who injected infrequently, were relatively recent initiates to injecting and whose numbers increased over the 3 years. Drug treatment and prevention services may need to explore alternative methods to respond effectively to these emerging trends.     

An approach for fabricating high-performance inductors onlow-resistivity substrates

Porous Si layers up to 250 μm in thickness are used to isolate spiral inductors from low resistivity substrates. Wafer curvature and secondary ion mass spectroscopy (SIMS) analysis are done to address the manufacturability issue of porous Si. Spiral inductors with a single level Al on 2 in, p-type substrates of 0.008 Ω-cm resistivity are demonstrated with Q<6 at 3 GHz for an L of ~8 nH. Large inductors with L~100 nH have been shown with the first resonance frequency at 1 GHz. The expected performance potential as well as factors that could be limiting the Q are discussed     

Cutaneous diphtheria in returning vacationers--mirror of inappropriate vaccination practice?

The causative agent for diphtheria is Corynebacterium diphtheriae, which is transmitted from person to person from the throat of carriers or from patients with active cutaneous diphtheria. The disease occurs in preexisting ulcers, but it may also appear on apparently normal skin. Although primary cutaneous diphtheria starts as a vesicle or pustule, most patients feature a reddish ulcer with undermined borders. The lesion is tender but hypesthesia develops after 2 weeks. The clinical diagnosis is based on the history of travelling in endemic regions and bacteriological studies. The current increase of diphtheria in the Western world is partly caused by rising tourism and a decline of booster vaccination in adults. After trauma with ulcerations of the skin we suggest to perform a booster vaccination not only for tetanus but also for diphtheria. In addition, persons travelling to endemic regions should receive a booster vaccination for tetanus and diphtheria, which is available as a combined preparation.     

IL-6-deficient mice resist myelin oligodendrocyte glycoprotein-induced autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is induced by immunization with myelin components including myelin oligodendrocyte glycoprotein (MOG). Myelin-specific Th1 cells enter the central nervous system (CNS) via binding of very late antigen 4 (VLA-4) to the endothelial vascular cell adhesion molecule 1 (VCAM-1). In the present study, mice with a homologous disruption of the gene encoding IL-6 are found to be resistant to MOG-induced EAE as evidenced by absence of clinical symptoms, minimal infiltration of CD3+ T cells and monocytes into the CNS and lack of demyelination. The failure to induce EAE in IL-6-/- mice is not due to the absence of priming, since lymphocytes of immunized IL-6-/- mice proliferate in response to MOG and produce pro-inflammatory cytokines including IL-2 and IFN-gamma. However, in MOG-immunized IL-6-/- mice, serum anti-MOG antibody titers were found to be drastically reduced. This observation is unlikely to be responsible for resistance to EAE, because B cell-deficient (microMT) mice proved to be fully susceptible to the disease. A striking difference between MOG-immunized wild-type (wt) and IL-6-/- mice was the expression of endothelial VCAM-1 and ICAM-1, which were dramatically up-regulated in the CNS in wt but not in IL-6-/- mice. Taking into account recent studies on the role of VCAM-1 in the entry of Th1 cells into the CNS, the absence of VCAM-1 on endothelial cells in IL-6-/- mice may explain their resistance to EAE.