Spatial Continuum Research Articles

SPATIAL ANALYSIS OF URBANIZATION PATTERNS: THE CASE OF LAND USE AND POPULATION DENSITY IN THE MILAN METROPOLITAN AREA

Efficiency in the provision of some large‐scale services motivates the administrative coordination of the urban functions at a more aggregate level. In Italy, the Metropolitan City (MC) has recently been introduced as an effective intermediate level between the region and the municipalities, to accommodate the integrated management of urban functions characterized by a broad spatial scope. The case of the Milan MC provides an opportunity for reflection on the extent to which the MC design should be envisioned, considering the urban morphology of an area. We analyze the patterns of urbanization, measured with population density and the share of urbanized area, considering the territories of the enlarged Milan metropolitan area, which includes the MC municipalities and of a contiguous province. The area under study can be considered a spatial continuum in which urbanization is markedly shaped by a core‐periphery pattern. We conclude that the MC design should have included all of the territories of the enlarged Milan metropolitan area, which are clearly interconnected with the Milan economy.

Prisms to travel in time: Investigation of time-space association through prismatic adaptation effect on mental time travel

Accumulating evidence suggests that humans process time and space in similar veins. Humans represent time along a spatial continuum, and perception of temporal durations can be altered through manipulations of spatial attention by prismatic adaptation (PA). Here, we investigated whether PA-induced manipulations of spatial attention can also influence more conceptual aspects of time, such as humans’ ability to travel mentally back and forward in time (mental time travel, MTT). Before and after leftward- and rightward-PA, participants projected themselves in the past, present or future time (i.e., self-projection), and, for each condition, determined whether a series of events were located in the past or the future with respect to that specific self-location in time (i.e., self-reference). The results demonstrated that leftward and rightward shifts of spatial attention facilitated recognition of past and future events, respectively. These findings suggest that spatial attention affects the temporal processing of the human self.

Coalescent inferences in conservation genetics: should the exception become the rule?

Genetic estimates of effective population size (Ne) are an established means to develop informed conservation policies. Another key goal to pursue the conservation of endangered species is keeping the connectivity across fragmented environments, to which genetic inferences of gene flow and dispersal greatly contribute. Most current statistical tools for estimating such population demographic parameters are based on Kingman's coalescent (KC). However, KC is inappropriate for taxa displaying skewed reproductive variance, a property widely observed in natural species. Coalescent models that consider skewed reproductive success-called multiple merger coalescents (MMCs)-have been shown to substantially improve estimates of Ne when the distribution of offspring per capita is highly skewed. MMCs predictions of standard population genetic parameters, including the rate of loss of genetic variation and the fixation probability of strongly selected alleles, substantially depart from KC predictions. These extended models also allow studying gene genealogies in a spatial continuum, providing a novel theoretical framework to investigate spatial connectivity. Therefore, development of statistical tools based on MMCs should substantially improve estimates of population demographic parameters with major conservation implications.

Nonultralocality and causality in the relational framework of canonical quantum gravity

The relational framework of canonical quantum gravity with nonultralocal constraints is explored. After demonstrating the absence of anomalies, a spatially discretized version of the relational framework is introduced. This allows the application of Lieb-Robinson bounds to on-shell monotonic gauge flow when there is a continuous external ``time'' parameter. An explicit Lieb-Robinson bound is derived for the differential on-shell evolution of the operator norm of the commutator of discretized Dirac observables, demonstrating how a local light conelike causal structure emerges. Ultralocal constraints do not permit such a structure to arise via Lieb-Robinson bounds. Gauge and ($3+1$)-diffeomorphism invariance of the light cone is discussed along with the issues of quantum fluctuations, the nature of the nonlocalities, the spatial continuum limit, and the possible links to noncommutative geometry.

Culturally inconsistent spatial structure reduces learning

Human adults tend to use a spatial continuum to organize any information they consider to be well-ordered, with a sense of initial and final position. The directionality of this spatial mapping is mediated by the culture of the subject, largely as a function of the prevailing reading and writing habits (for example, from left-to-right for English speakers or right-to-left for Hebrew speakers). In the current study, we tasked American and Israeli subjects with encoding and recalling a set of arbitrary pairings, consisting of frequently ordered stimuli (letters with shapes: Experiment 1) or infrequently ordered stimuli (color terms with shapes: Experiment 2), that were serially presented in a left-to-right, right-to-left, or central-only manner. The subjects were better at recalling information that contained ordinal stimuli if the spatial flow of presentation during encoding matched the dominant directionality of the subjects' culture, compared to information encoded in the non-dominant direction. This phenomenon did not extend to infrequently ordered stimuli (e.g., color terms). These findings suggest that adults implicitly harness spatial organization to support memory, and this harnessing process is culturally mediated in tandem with our spatial biases.

Demographic inference under the coalescent in a spatial continuum

Understanding population dynamics from the analysis of molecular and spatial data requires sound statistical modeling. Current approaches assume that populations are naturally partitioned into discrete demes, thereby failing to be relevant in cases where individuals are scattered on a spatial continuum. Other models predict the formation of increasingly tight clusters of individuals in space, which, again, conflicts with biological evidence. Building on recent theoretical work, we introduce a new genealogy-based inference framework that alleviates these issues. This approach effectively implements a stochastic model in which the distribution of individuals is homogeneous and stationary, thereby providing a relevant null model for the fluctuation of genetic diversity in time and space. Importantly, the spatial density of individuals in a population and their range of dispersal during the course of evolution are two parameters that can be inferred separately with this method. The validity of the new inference framework is confirmed with extensive simulations and the analysis of influenza sequences collected over five seasons in the USA.

Being (un)moved by mental time travel.

Mental imagery of events in the past or future, and of unpleasant or pleasant events, has been found to lead to spontaneous backward/forward bodily motions. Both time and emotion are represented along a spatial continuum, and activation of these representations seems to be simulated in spontaneous changes in body posture. We performed a conceptual replication and extension of an earlier study by Miles, Nind, and Macrae (2010) who reported clear postural effects when thinking of the past and the future. We additionally tested whether changes in posture appear when thinking of an emotional event. Volunteers engaged in mental imagery, involving combinations of time intervals and emotions. We simultaneously recorded center-of-pressure (COP) changes. Results revealed neither an effect of imagery of time nor of emotion on body posture. We conclude that embodied effects of imagery of abstract items on body posture may be less robust than suggested by previous literature.

Weakly bound nuclei: Exotic ground state properties and collective excitations

Weakly bound nuclei are open quantum many-body systems and can have exotic structures and dynamics in contrast to our knowledges of stable nuclei. Currently the related studies are among the central topics in nuclear physics and are important for further improvements of nuclear theory and understandings of element enrichment processes in astrophysical environments. Since the improvements of intensity and quality of radioactive nuclear beams are very difficult, theoretical studies will be very helpful for planning experiments and the interpretation of results. Here we review recent developments of continuum density functional theory and studies of weakly bound nuclei. The theoretical challenge is to self-consistently describe the weak-binding effects, exotic shapes, continuum effects and dynamics together. To this end, our main work is to solve the Hartree-Fock-Bogoliubov equation in non-spherical coordinate- spaces and then to describe the ground state properties as well as collective excitations of weakly bound nuclei. In the 2D lattice, we solved the HFB equation with the B-spline techniques. More recently, we solved the HFB equation in the 3D coordinate-space with the adaptive multi-resolution multi-wavelet techniques, which is novel and much more efficient. Based on our calculations, we discussed the exotic egg-like deformed halo structures, the core-halo deformation decoupling, and the role of continuum contributions. We also see pairing density distributions have remarkable deformed halo structures. The deformed cores are not so favorable for the formation of 2 n -halos, in particular heavy 2 n -halos. The non-resonant continuum rather than the resonant continuum is mainly responsible for halo features. With the quasiparticle blocking calculations, we also studied the deformed 1 n -halo nuclei, in which the pairing density is unusual due to the spin polarization. In addition, we developed the deformed continuum FAM-QRPA calculations in coordinate spaces and studied the emergent soft monopole collective excitations. The soft collective modes are unique in weakly bound nuclei and are useful for studies of nuclear properties in extreme conditions. Compared to the conventional QRPA diagonalization method, the FAM-QRPA solves the QRPA equation iteratively and is more efficient. Otherwise the deformed QRPA calculations with continuum would be very challenging. We see the pairing density halos and non-resonant continuum play an important role in these soft collective excitations. Our studies involved large coordinate-space calculations in Tianhe supercomputers to take into account shape deformations, large spatial extensions and continuum spectra. Otherwise, calculations within small coordinate spaces would produce a coarse continuum discretization and even false resonance peaks. Finally we give some persectives on studies of weakly bound nuclei and our plans. Since weakly bound nuclei exhibit few-body physics in many-body systems, the conventional shell-structure picture breaks down in this respect. Theorefore new many-body techniques, time-dependent 3D dynamics and improved effective interactions are very desirable. The studies of weakly bound nuclei as open quantum systems that involve threshold effects and continuum contributions can have broad interdisciplinary interests.

Demographic inference under a spatially continuous coalescent model.

In contrast with the classical population genetics theory that models population structure as discrete panmictic units connected by migration, many populations exhibit heterogeneous spatial gradients in population connectivity across semi-continuous habitats. The historical dynamics of such spatially structured populations can be captured by a spatially explicit coalescent model recently proposed by Etheridge (2008) and Barton et al. (2010a, 2010b) and whereby allelic lineages are distributed in a two-dimensional spatial continuum and move within this continuum based on extinction and coalescent events. Though theoretically rigorous, this model, which we here refer to as the continuum model, has not yet been implemented for demographic inference. To this end, here we introduce and demonstrate a statistical pipeline that couples the coalescent simulator of Kelleher et al. (2014) that simulates genealogies under the continuum model, with an approximate Bayesian computation (ABC) framework for parameter estimation of neighborhood size (that is, the number of locally breeding individuals) and dispersal ability (that is, the distance an offspring can travel within a generation). Using empirically informed simulations and simulation-based ABC cross-validation, we first show that neighborhood size can be accurately estimated. We then apply our pipeline to the South African endemic shrub species Berkheya cuneata to use the resulting estimates of dispersal ability and neighborhood size to infer the average population density of the species. More generally, we show that spatially explicit coalescent models can be successfully integrated into model-based demographic inference.

Nonlinear Dynamics Analysis of a Continuum Rotor through Generalized Harmonic Balance Method

The dynamics of a continuum rotor system excited by nonlinear oilfilm force and electromagnetic force is investigated through the Generalized Harmonic Balance Method. The governing differential equation of the continuum rotor system is reduced through the Galerkin’s approximation method. Firstly, the motion in Y-direction is considered as the response of a planar continuum rotor. The analytical periodic motion is obtained and the bifurcation and stability is determined. Secondly, the dynamical model of a spatial continuum rotor is studied. The stability and bifurcation of the analytical periodic motion is obtained and compared to numerical results to show the accuracy of the Generalized Harmonic Balance Method.

The Sun as a planet-host star: proxies fromSDOimages for HARPS radial-velocity variations

The Sun is the only star whose surface can be directly resolved at high resolution, and therefore constitutes an excellent test case to explore the physical origin of stellar radial-velocity (RV) variability. We present HARPS observations of sunlight scattered off the bright asteroid 4/Vesta, from which we deduced the Sun's activity-driven RV variations. In parallel, the HMI instrument onboard the Solar Dynamics Observatory provided us with simultaneous high spatial resolution magnetograms, Dopplergrams, and continuum images of the Sun in the Fe I 6173A line. We determine the RV modulation arising from the suppression of granular blueshift in magnetised regions and the flux imbalance induced by dark spots and bright faculae. The rms velocity amplitudes of these contributions are 2.40 m/s and 0.41 m/s, respectively, which confirms that the inhibition of convection is the dominant source of activity-induced RV variations at play, in accordance with previous studies. We find the Doppler imbalances of spot and plage regions to be only weakly anticorrelated. Lightcurves can thus only give incomplete predictions of convective blueshift suppression. We must instead seek proxies that track the plage coverage on the visible stellar hemisphere directly. The chromospheric flux index R'_HK derived from the HARPS spectra performs poorly in this respect, possibly because of the differences in limb brightening/darkening in the chromosphere and photosphere. We also find that the activity-driven RV variations of the Sun are strongly correlated with its full-disc magnetic flux density, which may become a useful proxy for activity-related RV noise.

A Mathematical Model for the Proliferation, Accumulation and Spread of Pathogenic Proteins Along Neuronal Pathways with Locally Anomalous Trapping

There is growing evidence that many neurodegenerative disease processes involve the proliferation, accumulation and spread of pathogenic proteins. The transport of proteins in the brain is typically hindered on small scales by micro-domain traps and binding sites but it may be enhanced on larger scales by neuronal pathways identified as white matter transport networks. We have introduced a mathematical network model to simulate a pathogenic protein neurodegenerative disease in the brain taking into account the anomalous transport. The proliferation and accumulation of pathogenic proteins is modelled using a set of reaction kinetics equations on the nodes of a network. Transport of the proteins on the network is modelled as a continuous time random walk with power law distributed waiting times on the nodes. This power law waiting time distribution is shown to be consistent with anomalously slowed diffusion on local scales but transport is enhanced on larger scales by the jumps between nodes. The model reveals that the disease spreads as a propagating front throughout the brain. The anomalous behaviour leads to a lessor variation in the concentration of pathogenic proteins. The enhanced transport on the network ensures that the approach to equilibrium is dominated by the short time behaviour of the waiting time density, hence the effects of subdiffusion are not as pronounced as in a spatial continuum.

ゴム皮膚層に3本のワイヤ駆動機構を内蔵する空間型連続体マニピュレータ

ゴム皮膚層に3本のワイヤ駆動機構を内蔵する空間型連続体マニピュレータ

Spatial Congruity Effects Reveal Metaphorical Thinking, not Polarity Correspondence

Spatial congruity effects have often been interpreted as evidence for metaphorical thinking, but an alternative account based on polarity correspondence (a.k.a. markedness) has challenged this view. Here we compared metaphor- and polarity-correspondence-based explanations for spatial congruity effects, using musical pitch as a testbed. In one experiment, English speakers classified high- and low-frequency pitches as “high” and “low,” or as “front” and “back,” to determine whether space-pitch congruity effects could be elicited by any marked spatial continuum. Although both pairs of terms describe bipolar spatial continuums, we found congruity effects only for high/low judgments, indicating that markedness is not sufficient to produce space-pitch congruity effects. A second experiment confirmed that there were no space-pitch congruity effects for another pair of terms that have clear markedness (big/small), but which do not denote spatial height. By contrast, this experiment showed congruity effects for words that cued an appropriate vertical spatial schema (tall/short), even though these words are not used conventionally in English to describe pitches, ruling out explanations for the observed pattern of results based on verbal polysemy. Together, results suggest that space-pitch congruity effects reveal metaphorical uses of spatial schemas, not polarity correspondence effects.

Urban Political Ecology

As urban environments transform across the globe, debates over urban nature and its future forms have introduced important critical questions. How, for instance, do we study emergent, dynamic configurations of nature and culture in cities? How do we conceptualize the city as a field site when urbanization encompasses the full spatial continuum from city to countryside? How do we understand the place of history in an environmental era often categorized as unprecedented? This article traces political ecology from its noncity origins to its present engagements with urban life and forms. It argues that ethnographic work both enriches and complicates recent debates about the urban past, present, and future, and it calls for more vigorous and refined anthropological engagement with the biophysical sciences, the theoretical and methodological challenges of scale, and the work of historical contextualization in the history-evasive era now widely known as the Anthropocene.

Topology optimization of spatial continuum structures made of nonhomogeneous material of cubic symmetry

Topology optimization of spatial continuum structures made of nonhomogeneous material of cubic symmetry

Duration and numerical estimation in right brain-damaged patients with and without neglect: Lack of support for a mental time line

Previous studies have shown that left neglect patients are impaired when they have to orient their attention leftward relative to a standard in numerical comparison tasks. This finding has been accounted for by the idea that numerical magnitudes are represented along a spatial continuum oriented from left to right with small magnitudes on the left and large magnitudes on the right. Similarly, it has been proposed that duration could be represented along a mental time line that shares the properties of the number continuum. By comparing directly duration and numerosity processing, this study investigates whether or not the performance of neglect patients supports the hypothesis of a mental time line. Twenty-two right brain-damaged patients (11 with and 11 without left neglect), as well as 11 age-matched healthy controls, had to judge whether a single dot presented visually lasted shorter or longer than 500ms and whether a sequence of flashed dots was smaller or larger than 5. Digit spans were also assessed to measure verbal working memory capacities. In duration comparison, no spatial-duration bias was found in neglect patients. Moreover, a significant correlation between verbal working memory and duration performance was observed in right brain-damaged patients, irrespective of the presence or absence of neglect. In numerical comparison, only neglect patients showed an enhanced distance effect for numerical magnitude smaller than the standard. These results do not support the hypothesis of the existence of a mental continuum oriented from left to right for duration. We discuss an alternative account to explain the duration impairment observed in right brain-damaged patients.

Two steps to space for numbers.

Two steps to space for numbers.

Particle partition entanglement of bosonic Luttinger liquids

We consider the R\'{e}nyi entanglement entropy of bosonic Luttinger liquids under a particle bipartition and demonstrate that the leading order finite-size scaling is logarithmic in the system size with a prefactor equal to the inverse Luttinger parameter. While higher order corrections involve a microscopic length scale, the leading order scaling depends only on this sole dimensionless parameter which characterizes the low energy quantum hydrodynamics. This result contrasts the leading entanglement entropy scaling under a spatial bipartition, for which the coefficient is universal and independent of the Luttinger parameter. Using quantum Monte Carlo calculations, we explicitly confirm the scaling predictions of Luttinger liquid theory for the Lieb-Liniger model of $\delta$-function interacting bosons in the one dimensional spatial continuum.

Modeling focal epileptic activity in the Wilson-cowan model with depolarization block.

Measurements of neuronal signals during human seizure activity and evoked epileptic activity in experimental models suggest that, in these pathological states, the individual nerve cells experience an activity driven depolarization block, i.e. they saturate. We examined the effect of such a saturation in the Wilson–Cowan formalism by adapting the nonlinear activation function; we substituted the commonly applied sigmoid for a Gaussian function. We discuss experimental recordings during a seizure that support this substitution. Next we perform a bifurcation analysis on the Wilson–Cowan model with a Gaussian activation function. The main effect is an additional stable equilibrium with high excitatory and low inhibitory activity. Analysis of coupled local networks then shows that such high activity can stay localized or spread. Specifically, in a spatial continuum we show a wavefront with inhibition leading followed by excitatory activity. We relate our model simulations to observations of spreading activity during seizures.Electronic Supplementary MaterialThe online version of this article (doi:10.1186/s13408-015-0019-4) contains supplementary material 1.