Intrinsic instability of flame–acoustic coupling

This paper shows that a flame can be an intrinsically unstable acoustic element. The finding is clarified in the framework of an acoustic network model, where the flame is described by an acoustic scattering matrix. The instability of the flame acoustic coupling is shown to become dominating in the limit of no acoustic reflections. This is in contrast to classical standing-wave thermoacoustic modes, which originate from the positive feedback loop between system acoustics and the flame. These findings imply that the effectiveness of passive thermoacoustic damping devices is limited by the intrinsic stability properties of the flame.     

Wind power and the NIMBY-myth: institutional capacity and the limited significance of public support

In many countries, the development of wind power capacity has proceeded more slowly than expected. Levels of public acceptance are usually considered primary indicators of support for wind power within society. Surveys generally show strong overall public support for wind power, while concrete projects are felt to suffer from the Not-In-My-Backyard (NIMBY) syndrome. This paper questions the significance of these outcomes. It argues that other barriers to wind power implementation exist beyond attitudes among the population. The argument is made that institutional factors have a greater impact on wind energy facility siting. We will discuss two examples of how institutional factors shape the level of support when implementing wind power.     

Axiomatizing the Logical Core of XPath 2.0

The first aim of this paper is to present the logical core of XPath 2.0: a logically clean, decidable fragment, which includes most navigational features of XPath 2.0 (complex counting conditions and data joins are not supported, as they lead to undecidability). The second aim is to provide a list of equations completely axiomatizing query equivalence in this language (i.e., all other query equivalences can be derived from these). A preliminary version of this paper was published in the proceedings of ICDT 2007. We would like to thank Jan Hidders for pointing us to the interesting question of stronger forms of completeness (cf. Sect. 4.3). We would also like to thank the anonymous reviewers for their extensive comments, which have greatly improved the quality of the paper. The first author is supported by NWO grant 639.021.508.     

Learning in a changing environment.

Multiple cue probability learning studies have typically focused on stationary environments. We present 3 experiments investigating learning in changing environments. A fine-grained analysis of the learning dynamics shows that participants were responsive to both abrupt and gradual changes in cue–outcome relations. We found no evidence that participants adapted to these types of change in qualitatively different ways. Also, in contrast to earlier claims that these tasks are learned implicitly, participants showed good insight into what they learned. By fitting formal learning models, we investigated whether participants learned global functional relationships or made localized predictions from similar experienced exemplars. Both a local (the associative learning model) and a global learning model (the Bayesian linear filter) fitted the data of the first 2 experiments. However, the results of Experiment 3, which was specifically designed to discriminate between local and global learning models, provided more support for global learning models. Finally, we present a novel model to account for the cue competition effects found in previous research and displayed by some of our participants. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Power savings with resonant PMLCD driving

A possible solution for decreasing the ac power dissipation in PMLCD driving is to use an RLC resonant‐drive approach. The achievable power savings depends on several parameters: the LCD material properties, the display size, the frame refresh rate, the driver‐IC technology, etc. A good knowledge of the different parameters is crucial to determining how much power can potentially be saved with resonant driving. In this paper, the influence of these parameters is theoretically derived. Using the essential formulas, a resonant‐driver IC for a 48 × 100 TN‐PMLCD was designed and experimentally verified: a power savings of 45% was obtained.     

Castration Reduces the Effect of Serotonin-1A Receptor Stimulation on Prepulse Inhibition in Rats.

This study examined the interaction between hormones and serotonin-1A (5-HT1A) receptor modulation of prepulse inhibition (PPI) of the acoustic startle response. Male and female rats were gonadectomized; some castrated rats received testosterone- or estrogen-filled implants. Rats were randomly injected with saline or 0.02 or 0.50 mg/kg 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a selective 5-HT1A receptor agonist. All rats showed a dose-dependent disruption of PPI in response to 8-OH-DPAT. In untreated castrated rats, this disruption was significantly reduced (33% compared with 78% in sham-operated rats). Testosterone treatment reversed this reduction, but estrogen was less effective. Ovariectomized and sham-operated rats showed similar PPI in response to 8-OH-DPAT. These data suggest that the effect of 8-OH-DPAT on PPI in male rats depends on circulating hormone levels, particularly testosterone. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Beyond imprisonment of meaning: Technology facilitating redefining

Defining is a natural and necessary response to an ambiguous world, but causes fixation of categories and perspectives. On the basis of two earlier studies of project groups, we came to argue that redefining, and hence constructing various ways in which one perceives and understands something, enables groups to overcome imprisonment in meaning, establishing continuous development and flexibility. In this article, we first build a rationale for facilitating a process of redefining, to be taken into account when designing technology. Departing from this rationale, we discuss features of groupware technology that permit change by being flexible, and evoke redefining by engaging the user more actively. In so doing, we argue to think along new lines in the design of communication and collaboration technology. This paper proposes a specific perspective on technology, facilitating groups to engage in a productive, creative fashion of exploiting meaning potential.     

In situ wear studies of surface micromachined interfaces subject to controlled loading

Friction and wear are major limiting factors for the development and commercial implementation of devices fabricated by surface micromachining techniques. These tribological properties are studied using a polycrystalline silicon nanotractor device, which provides abundant, quantitative information about friction and wear at an actual microelectromechanical system (MEMS) interface. This in situ approach to measuring tribological properties of MEMS, combined with high-resolution atomic force microscope (AFM) images of wear tracks, provides insight into the effects of different MEMS surface processing on wear. In particular, monolayer coatings have a significant positive effect, while surface texturing does not strongly affect performance.     

Impact of a Stereocentre Inversion in Cyclic Lipodepsipeptides from the Viscosin Group: A Comparative Study of the Viscosinamide and Pseudodesmin Conformation and Self‐Assembly

The viscosin group covers a series of cyclic lipodepsipeptides (CLPs) produced by Pseudomonas bacteria, with a range of biological functions and antimicrobial activities. Their oligopeptide moieties are composed of both L ‐ and D ‐amino acids. Remarkably, the Leu5 amino acid—centrally located in the nonapeptide sequence—is the sole residue found to possess either an L or D configuration, depending on the producing strain. The impact of this D /L switch on the solution conformation was investigated by NMR‐restrained molecular modelling of the epimers pseudodesmin A and viscosinamide A. Although the backbone fold remained unaffected, the D /L switch adjusted the segregation between hydrophobic and hydrophilic residues, and thus the amphipathicity. It also influenced the self‐assembly capacity in organic solvents. Additionally, several new minor variants of viscosinamide A from Pseudomonas fluorescens DR54 were identified, and an NMR assay is proposed to assess the presence of either an L ‐ or D ‐Leu5.