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"Ulrich, R."
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What strategy should an individual follow in a heterogeneous environment when its phenotype is not optimized for its current environment: make changes to the environment (habitat construction), move to a different place (habitat choice), or both? Scheiner et al. used an individual-based model to investigate the interaction of habitat choice and habitat construction. In most situations, habitat construction was superior to either habitat selection or a mixed strategy.
Journal Article
A genome-wide association scan of nonsynonymous SNPs identifies a susceptibility variant for Crohn disease in ATG16L1
We performed a genome-wide association study of 19,779 nonsynonymous SNPs in 735 individuals with Crohn disease and 368 controls. A total of 7,159 of these SNPs were informative. We followed up on all 72 SNPs with
P
≤ 0.01 with an allele-based disease association test in 380 independent Crohn disease trios, 498 Crohn disease singleton cases and 1,032 controls. Disease association of rs2241880 in the autophagy-related 16-like 1 gene (
ATG16L1
) was replicated in these samples (
P
= 4.0 × 10
−8
) and confirmed in a UK case-control sample (
P
= 0.0004). By haplotype and regression analysis, we found that marker rs2241880, a coding SNP (T300A), carries virtually all the disease risk exerted by the
ATG16L1
locus. The
ATG16L1
gene encodes a protein in the autophagosome pathway that processes intracellular bacteria. We found a statistically significant interaction with respect to Crohn disease risk between rs2241880 and the established
CARD15
susceptibility variants (
P
= 0.039). Together with the lack of association between rs2241880 and ulcerative colitis (
P
> 0.4), these data suggest that the underlying biological process may be specific to Crohn disease.
Journal Article
Holistic Package Design and Consumer Brand Impressions
This article develops empirically based guidelines to assist managers in selecting or modifying package designs for achieving desired consumer responses. Seven studies identify the key types of package designs, including the factors that differentiate those package designs, and determine how these holistic designs are related to consumer brand impressions. The selection of package designs can be simplified with the use of five holistic types: massive, contrasting, natural, delicate, and nondescript designs. Sincere brands should have natural package designs, exciting brands should have contrasting designs, competent brands should have delicate designs, sophisticated brands should have natural or delicate designs, and rugged brands should have contrasting or massive designs. The authors discuss the potential trade-offs among the impressions created by holistic design types and illustrate their findings with numerous real packages.
Journal Article
Energy flux determines magnetic field strength of planets and stars
Magnetic field generation
Some planets and many stars have magnetic fields that are generated by a convection-driven dynamo process. Stellar fields, known from their effect on the emitted light, are often 1,000 times stronger than that of Earth, so if the dynamo mechanism is similar for all these bodies, it is one that can produce field strengths varying over three orders of magnitude. Christensen
et al
. propose a simple law relating field strength to energy flux that applies to stars and planets alike, provided they are rotating sufficiently rapidly. Computer models of the geodynamo and stellar dynamos support the law, and its predictions agree with the observed fields of Earth, Jupiter and two groups of stars. Objects of intermediate mass, brown dwarf stars and supermassive extrasolar planets, should have strong detectable magnetic fields courtesy of this mechanism — but our Sun rotates too slowly to fit this template.
The magnetic fields of Earth and Jupiter, along with those of rapidly rotating, low-mass stars, are generated by convection-driven dynamos that may operate similarly, although the field strengths vary. The critical factor unifying field generation in such different objects, while still causing a large variation, has been unclear. This paper reports an extension of a scaling law derived from geodynamo models to rapidly rotating stars. The unifying principle is that the energy flux available for generating the magnetic field sets the field strength.
The magnetic fields of Earth and Jupiter, along with those of rapidly rotating, low-mass stars, are generated by convection-driven dynamos that may operate similarly
1
,
2
,
3
,
4
(the slowly rotating Sun generates its field through a different dynamo mechanism
5
). The field strengths of planets and stars vary over three orders of magnitude, but the critical factor causing that variation has hitherto been unclear
5
,
6
. Here we report an extension of a scaling law derived from geodynamo models
7
to rapidly rotating stars that have strong density stratification. The unifying principle in the scaling law is that the energy flux available for generating the magnetic field sets the field strength. Our scaling law fits the observed field strengths of Earth, Jupiter, young contracting stars and rapidly rotating low-mass stars, despite vast differences in the physical conditions of the objects. We predict that the field strengths of rapidly rotating brown dwarfs and massive extrasolar planets are high enough to make them observable.
Journal Article
Approaching a realistic force balance in geodynamo simulations
Earth sustains its magnetic field by a dynamo process driven by convection in the liquid outer core. Geodynamo simulations have been successful in reproducing many observed properties of the geomagnetic field. However, although theoretical considerations suggest that flow in the core is governed by a balance between Lorentz force, rotational force, and buoyancy (called MAC balance for Magnetic, Archimedean, Coriolis) with only minute roles for viscous and inertial forces, dynamo simulations must use viscosity values that are many orders of magnitude larger than in the core, due to computational constraints. In typical geodynamo models, viscous and inertial forces are not much smaller than the Coriolis force, and the Lorentz force plays a subdominant role; this has led to conclusions that these simulations are viscously controlled and do not represent the physics of the geodynamo. Here we show, by a direct analysis of the relevant forces, that a MAC balance can be achieved when the viscosity is reduced to values close to the current practical limit. Lorentz force, buoyancy, and the uncompensated (by pressure) part of the Coriolis force are of very similar strength, whereas viscous and inertial forces are smaller by a factor of at least 20 in the bulk of the fluid volume. Compared with nonmagnetic convection at otherwise identical parameters, the dynamo flow is of larger scale and is less invariant parallel to the rotation axis (less geostrophic), and convection transports twice as much heat, all of which is expected when the Lorentz force strongly influences the convection properties.
Journal Article
Digest
What strategy should an individual follow when faced with a suboptimal environment: change the environment, adapt to the environment, or both? Scheiner et al. used an individual-based model to address the interaction of plasticity and habitat construction with different life histories in a heterogeneous environment. In most situations, habitat construction was superior to either plasticity or a mixed strategy, but not always, and specific conditions may favor plasticity.
Journal Article
Is Beauty in the Aisles of the Retailer? Package Processing in Visually Complex Contexts
•We examine how context visual complexity affects a package's attractiveness.•Low Visual complexity of a context increases a package's attractiveness.•This effect is particularly evident with inherently attractive packages.•Processing fluency mediates the context complexity–attractiveness relation.•Individual field dependence and shopping goals are important moderators.
Visual appeal is an important consideration in the design of brand packages because attractiveness guides behavior. The visual complexity of a context (i.e., the quantity, irregularity, detail, and dissimilarity of objects) in which a retailer displays a package may impact its attractiveness by influencing attention and processing fluency. Employing consumer samples, and stimuli ranging from the abstract to the realistic, three studies provide evidence that people process a package more fluently, thus increasing its attractiveness, when it is presented in a low rather than high complexity context. This effect is more pronounced with inherently appealing packages, and with people who are more field-dependent or pursuing utilitarian shopping goals. Study 1 establishes effects by employing psychometric measures and abstract stimuli; study 2 corroborates findings with another product category and realistic stimuli; and study 3 complements psychometric measures with eye tracking data to demonstrate that visually more complex contexts divert viewer attention, hereby lowering processing fluency and target attractiveness. The authors discuss the theoretical contribution and strategic insights the research provides for retailers, brand managers, and designers.
Journal Article
A deep dynamo generating Mercury’s magnetic field
Mercury: playing the field
The latest numerical models of the geodynamo can account for the behaviour of Earth's magnetic field pretty well: Mercury has proved a harder nut to crack. Like Earth, it has a dipolar magnetic field, probably generated by a dynamo from convective motions in the planet's liquid iron core. But Mercury's field is a hundred times weaker than Earth's, and this poses a problem for the dynamo theory. A new explanation for the discrepancy has been proposed, accounting for both the observed field strength and the magnetic field geometry observed during the Mariner 10 flybys. The new model assumes that the dynamo operates only deep down in the core, where it generates a strong field. The outer regions of the core are stably layered, so do not convect heat, but they are electrically conducting and the dynamo-generated field is therefore strongly damped. Data from NASA's Messenger probe,
en route
to Mercury, and ESA's planned Bepi Colombo mission should provide a thorough test for the model.
Mercury has a global magnetic field of internal origin and it is thought that a dynamo operating in the fluid part of Mercury’s large iron core is the most probable cause. However, the low intensity of Mercury’s magnetic field—about 1% the strength of the Earth’s field—cannot be reconciled with an Earth-like dynamo. With the common assumption that Coriolis and Lorentz forces balance in planetary dynamos
1
, a field thirty times stronger is expected. Here I present a numerical model of a dynamo driven by thermo-compositional convection associated with inner core solidification. The thermal gradient at the core–mantle boundary is subadiabatic
2
,
3
, and hence the outer region of the liquid core is stably stratified with the dynamo operating only at depth, where a strong field is generated. Because of the planet’s slow rotation the resulting magnetic field is dominated by small-scale components that fluctuate rapidly with time. The dynamo field diffuses through the stable conducting region, where rapidly varying parts are strongly attenuated by the skin effect, while the slowly varying dipole and quadrupole components pass to some degree. The model explains the observed structure and strength of Mercury’s surface magnetic field and makes predictions that are testable with space missions both presently flying and planned.
Journal Article