Dynamic Localization Conditions Research Articles

Modeling metabolic networks of individual bacterial agents in heterogeneous and dynamic soil habitats (IndiMeSH).

Natural soil is characterized as a complex habitat with patchy hydrated islands and spatially variable nutrients that is in a constant state of change due to wetting-drying dynamics. Soil microbial activity is often concentrated in sparsely distributed hotspots that contribute disproportionally to macroscopic biogeochemical nutrient cycling and greenhouse gas emissions. The mechanistic representation of such dynamic hotspots requires new modeling approaches capable of representing the interplay between dynamic local conditions and the versatile microbial metabolic adaptations. We have developed IndiMeSH (Individual-based Metabolic network model for Soil Habitats) as a spatially explicit model for the physical and chemical microenvironments of soil, combined with an individual-based representation of bacterial motility and growth using adaptive metabolic networks. The model uses angular pore networks and a physically based description of the aqueous phase as a backbone for nutrient diffusion and bacterial dispersal combined with dynamic flux balance analysis to calculate growth rates depending on local nutrient conditions. To maximize computational efficiency, reduced scale metabolic networks are used for the simulation scenarios and evaluated strategically to the genome scale model. IndiMeSH was compared to a well-established population-based spatiotemporal metabolic network model (COMETS) and to experimental data of bacterial spatial organization in pore networks mimicking soil aggregates. IndiMeSH was then used to strategically study dynamic response of a bacterial community to abrupt environmental perturbations and the influence of habitat geometry and hydration conditions. Results illustrate that IndiMeSH is capable of representing trophic interactions among bacterial species, predicting the spatial organization and segregation of bacterial populations due to oxygen and carbon gradients, and provides insights into dynamic community responses as a consequence of environmental changes. The modular design of IndiMeSH and its implementation are adaptable, allowing it to represent a wide variety of experimental and in silico microbial systems.

Second-order tunneling under the dynamic localization condition of two particles in driven one-dimensional lattices with an impurity

We investigate the effect of the interplay between the interatomic interaction and impurity on dynamic localization for two interacting bosons held in driven one-dimensional lattices with an impurity. We find that the interplay of the interatomic interaction and impurity can induce second-order tunneling under the dynamic localization condition. In the resonant regime, where the impurity potential is equal to a multiple of the driving frequency, two bosons form a stable bound pair and the dominant tunneling of the doublon in the paired state is a second-order process. In the non-resonant regime, the tunneling dynamics of the single boson in the unpaired state can also be a second-order process between the two nearest-neighbor sites of the impurity with the negligible impurity site population, and the other boson is localized in the initial site all the time. Our results provide a promising approach for controlling transport of realistic systems.

Household types as a tool to understand adaptive capacity: case studies from Cambodia, Lao PDR, Bangladesh and India

Supporting smallholder households to adapt to climate variability is a high priority for development agencies and national governments. Efforts to support climate adaptation in developing countries occur within highly dynamic contexts. Macro-level changes in national and regional economies manifest in dynamic local conditions, such as migration, changing household labour dynamics, market access and land-use options. Research aimed at developing adaptation options is often focused on particular activities or industries and struggles to take into account the broader, interrelated suite of household livelihood activities or the non-climate stressors driving change and adaptation. This paper explores the use of household types to (a) understand the diversity of household circumstances and (b) place agricultural adaptation options within the broader context of household livelihoods. Results from application in four countries are discussed, which highlight the utility of the method and identify broader level trends and drivers that are common challenges (experienced differently) across multiple contexts.

Growth Rate and Level Effects, the Stability of the Adjustment of Capacity to Demand and the Sraffian Supermultiplier

The paper presents a simple but complete formal version of the Sraffian supermultiplier model in which (i) growth is led by the autonomous components of demand that do not create capacity; (ii) private productive investment is an induced expenditure; and (iii) income distribution is exogenous. We show that the main results of the long-period and fully adjusted versions of the model in terms of growth rate and level effects are quite similar and therefore that such results in no way require the full adjustment of capacity to demand. We then analyze a simple set of sufficient dynamic local stability conditions that allow the long-period positions to gravitate towards the fully adjusted position in which capacity is adjusted to demand and that also provide the upper limit to demand-led growth paths. Finally, we show how some critics of the model have misinterpreted it as being supply-led and how this has led to a further confusion between the analysis of the tendency towards a constant value of the capacity-saving-determined warranted rate of growth and the proper stability analysis of the opposite process of adjusting capacity to demand (which tends to adjust the warranted rate endogenously to the growth rate of autonomous demand).

Low-frequency anomalies in dynamic localization

Quantum mechanical spreading of a particle hopping on tight binding lattices can be suppressed by the application of an external ac force, leading to periodic wave packet reconstruction. Such a phenomenon, referred to as dynamic localization (DL), occurs for certain ‘magic’ values of the ratio Γ = F0/ω between the amplitude F0 and frequency ω of the ac force. It is generally believed that in the low-frequency limit (ω → 0) DL can be achieved for an infinitesimally small value of the force F0, i.e. at finite values of Γ. Such normal behavior is found in homogeneous lattices as well as in inhomogeneous lattices of the Glauber–Fock (GF) type. Here we introduce a tight-binding lattice model with inhomogeneous hopping rates, referred to as a pseudo-GF lattice, which shows DL but fails to reproduce the normal low-frequency behavior of homogeneous and GF lattices. In pseudo-GF lattices, DL can be exactly realized; however, at the DL condition the force amplitude F0 remains finite as ω → 0. Such an anomalous behavior is explained in terms of a symmetry-breaking transition of an associated two-level non-Hermitian Hamiltonian that effectively describes the dynamics of the Hermitian lattice model.

Deriving currents on the one-dimensional lattice in the regime of dynamic localization

In this paper one deals with a transparent derivation of dynamic localization conditions for the electron on the 1D lattice proceeding irrespective of the concrete form of the periodic modulation of the time dependent electric field. This amounts to account for periodic zero minima generated in the time dependence of the mean square displacement (MSD). Related DL conditions have also been established by looking for the extremal points of the MSD. Interestingly enough, the conditions established in this manner are similar to the ones written down before for pure ac fields but exhibiting a rather unusual modulation. Related time dependent currents can be readily established, now by resorting to discrete derivatives. Our typical example is the dc-ac electric field. We found that in the regime of dynamic localization the MSD and the current get characterized by the same period, i.e by the period of the time dependent modulation. Moreover, the current crosses the time axis just in the maxima-locations of the MSD.

The influence of time-dependent electric and magnetic fields on the dynamic localization of lattice electrons

In this paper we deal with the derivation of dynamic localization conditions for electrons on the one-dimensional (1D) lattice under the influence of ac electric and magnetic fields of the same frequency. We resort, for convenience, to a tight-binding single-band Hamiltonian. Our emphasis is on a more fundamental theoretical understanding by investigating interplays between such fields and the nearest-neighbor hopping interactions characterizing the Hamiltonian. In general, such conditions get expressed in terms of infinite sums of binary products of Bessel functions of the first kind. These sums are hardly tractable, but we found that selecting in a suitable manner the phases of time-dependent modulations leads to controllable frequency-mixing effects providing appreciable simplifications. Such mixings concern competitions between the number of flux quanta and the quotients of field amplitudes and field frequencies. More exactly, tuning one of the mixed frequencies to zero opens the way to establishing the simplified dynamic localization conditions. By resorting again to the zeros of the Bessel function of zeroth order. This results in quickly tractable relationships between the amplitudes of electric and magnetic fields, the field frequency, and the zeros referred to just above. Pure field limits and superpositions between uniform electric and time-dependent magnetic fields are also discussed. Comments concerning the role of disorder and of the Coulomb interaction are also made.

On the dynamic localization conditions for dc–ac electric fields proceeding beyond thenearest-neighbour description

Dynamic localization conditions proceeding beyond the nearest-neighbour description havebeen established by applying the quasi-energy description. The general energydispersion laws one deals with concern a periodic but commensurable dc–ac field likeE0+E1f(t), forwhich f(t) = f(t+T) and ωB = Pω/Q. Here and ω = 2π/T stand for the Bloch and ac field frequencies, respectively, whileP and Q are mutually prime integers. A reasonable centre of band generalization of such conditionshas been proposed.

TIME DISCRETIZATION APPROACH TO DYNAMIC LOCALIZATION CONDITIONS

An alternative wavefunction to the description of the dynamic localization of a charged particle moving on a one-dimensional lattice under the influence of a periodic time dependent electric field is written down. For this purpose the method of characteristics such as applied by Dunlap and Kenkre [Phys. Rev. B34, 3625 (1986)] has been modified by using a different integration variable. Handling this wavefunction one is faced with the selection of admissible time values. This results in a conditionally exactly solvable problem, now by accounting specifically for the implementation of a time discretization working in conjunction with a related dynamic localization condition. In addition, one resorts to the strong field limit, which amounts to replace, to leading order, the large order zeros of the Bessel function J0(z), used before in connection with the cosinusoidal modulation, by integral multiples of π. Here z stands for the ratio between the field amplitude and the frequency. The modulation function of the electric field vanishes on the nodal points of the time grid, which stands for an effective field-free behavior. This opens the way to propose quickly tractable dynamic localization conditions for arbitrary periodic modulations. We have also found that the present time discretization approach produces the minimization of the mean square displacement characterizing the usual exact wavefunction. Other realizations and comparisons have also been presented.

Dynamic Localization Condition of Two Electrons in a Strongdc–ac Biased Quantum Dot Molecule

We present a perturbation investigation of dynamic localizationcondition of two electrons in a strong dc–ac biased quantum dotmolecule. By reducing the system to an Hubbard-type effective two-sitemodel and by applying Floquet theory, we find that the dynamicallocalization phenomenon occurs under certain values of the largestrength of the dc and ac field. This demonstrates the possibility ofusing appropriate dc–ac fields to manipulate dynamical localized statesin mesoscopic devices, which is an essential component of practicalschemes for quantum information processing. Our conclusion isinstructive to the field of quantum function devices.

Dynamic Localization Conditions of Bloch Electrons in Two-Mode ac Field

On the basis of analytical calculations for the dynamics of a Bloch electron in two-mode pure ac fields we find a localization condition of the Bloch electron on a localized state that either the ratio edE1/ω1 or edE2/ω2 of the ac fields is the root of the ordinary zero-order Bessel function J0 whenever the ratio of frequencies of two ac fields ω1/ω2 is not a rational number. The result is also extended to the multi-field case.

Domestic Architecture and Settlement Planning in Early and Middle Bronze Age Sicily: Thoughts on Innovation and Social Process

Significant advances in settlement archaeology in Bronze Age Sicily in recent years have provided greater opportunities to explore social dynamics in local communities. The full publication of several important residential and sacred sites, including La Muculufa, Monte Grande, Capo Graziano and I Faraglioni, Ustica enable close study of material assemblages within their architectural contexts. The relationship between social behavior and domestic architecture in Bronze Age Sicily is analyzed, focusing on the structuring of social interaction at multiple levels of social distance. Recent work has also demonstrated increasing contacts between Sicilian and east Mediterranean communities during the second millennium BC. Innovations, including widespread use of formally defined exterior household spaces, careful planning of shared public places, and imposing defensive structures, emerged in response to frame new kinds of interactions with outsiders and between community members. These new architectural forms developed unevenly, reflecting a variety of processes specific to local conditions. At Thapsos, new architectural forms appeared in the context of intensive contact with the Aegean world; at other sites such as I Faraglioni, Punta Milazzese and Mursia (Pantelleria) innovative architectural forms formalized traditional uses of domestic space in response to dynamic local conditions.

Dynamics of a superlattice with an impurity in a dc–ac electric field

Within a single-band tight-binding model, we investigate the dynamics of a one-dimensional semiconductor superlattice with an impurity driven by a dc–ac electric field. By numerically calculating the quasienergy spectrum and the probability propagators, we find that the dynamic localization condition is not destroyed by the impurity, but the local dynamics of the system is sensitively dependent on the relation of the impurity potential, the Bloch oscillation frequency and the ac field frequency. In appropriate circumstances, the dynamics of the system is dominated by resonant oscillations between the impurity and it nearest-neighbor sites. Such an effect might find important application for generating electromagnetic radiation and systematic study of localization phenomena.

Dynamics of a superlattice with an impurity in an ac electric field

Within a single-band tight-binding model, we investigate the dynamics of a one-dimensional semiconductor superlattice with an impurity under the action of an ac electric field. The long-time mean-square displacement is analytically obtained and the quasienergy spectrum is numerically calculated. We find that although the dynamic localization condition is not destroyed by the impurity, the quasienergy spectrum and corresponding local dynamics of the system are tuned dramatically by the ratio of the impurity potential to the ac field frequency. In particular, when the ratio becomes an integer, avoided crossing in the quasienergy spectrum occurs and the dynamics of the system is dominated by resonant oscillations between the impurity and its two nearest-neighbor sites. Such an effect is more favorable for experimental investigations of coherent oscillations of charged carriers.

Factors Influencing the Incorporation of Hazard Mitigation During Recovery from Disaster

This paper examines the factors promoting theadoption of mitigation measures during long-term recoveryfollowing Hurricane Hugo in the United States. Recovery fromdisaster offers opportunities for improving community resilienceto future disasters and for promoting sustainability. Variousdynamics during recovery, however, can interfere with mitigationof hazards. In this study the adoption of mitigation duringrecovery in three case communities after Hurricane Hugo isevaluated, with a focus on the influence of various regulations onhazard mitigation. There is a very strong connection betweendevelopment management and hazard mitigation; resourcemanagement also contributes to hazard mitigation. Conditionsthat influence advancement of hazard mitigation at thecommunity level include local leadership, a linkage betweenwell-established ways of doing things and new policies,adaptation to dynamic local conditions, monitoring andcompliance strategies tailored to suit local conditions, recognitionof local rights, and stakeholders' involvement in developingstrategies.

Motion of a Charged Particle in an Arbitrary Time-Dependent Electric Field with Alternating Intersite Interactions

The motion of a charged particle on a linear chain under the action of an electric field with alternating intersite interactions is investigated. Exact solutions for the Wannier state amplitudes, the propagators and the mean square displacement are obtained for the general case of an arbitrary time-dependent electric field, of which a electric field is only a special one. The dynamic localization condition is given for this special case. This condition would make the observation of dynamic localization effect possible.

Dynamic localization conditions of a charged particle in a dcac electric field

The motion of a charged particle on a discrete lattice under the action of a dcac electric field is investigated. The dynamic localization conditions for both the case of nearest-neighbor intersite interactions and long-range intersite interactions are obtained. The possibilities of observation of the dynamic localization effect are also discussed.