Decimation in Time and Space of Finite-Difference Time-Domain Schemes: Standard Isotropic Lossless Model

Finite-difference time-domain (FDTD) schemes permit changes in the grid density on selected regions of the wave propagation domain, which can reduce the computational load of the simulations. One possible alternative to varying the spatial density is to change the simulation temporal rate. This idea looks attractive when the wave signals exhibit pronounced bandwidth fluctuations across time. This is particularly true in sound synthesis, where a physically based acoustic resonator can be conveniently modeled using such schemes. To overcome the computational constraints that must be met by real-time distributed resonator models, this paper deals with the decimation in time and space of isotropic lossless finite-difference time-domain schemes holding conventional Nyquist-Shannon limits on the bandwidth of the wave signals. Formulas for the reconstruction of these signals at runtime over the interpolated grid are provided for both the 1D and 2D orthogonal case, depending on the ideal boundary conditions (either Neumann or Dirichlet) holding at each side of the grid in connection with the domain side lengths (either even or odd). Together, the boundaries and size determine the type of Discrete Cosine Transform used in the corresponding interpolation formula. Numerical artifacts arising as a consequence of decimating in space in 2D are discussed in terms of dispersion error and aliasing. Considerations concerning the temporal reconstruction of components lying at the decimated Nyquist frequency are addressed in the conclusion

Eliciting the Functional Taxonomy from protein annotations and taxa

The advances of omics technologies have triggered the production of an enormous volume of data coming from thousands of species. Meanwhile, joint international efforts like the Gene Ontology (GO) consortium have worked to provide functional information for a vast amount of proteins. With these data available, we have developed FunTaxIS, a tool that is the first attempt to infer functional taxonomy (i.e. how functions are distributed over taxa) combining functional and taxonomic information. FunTaxIS is able to define a taxon specific functional space by exploiting annotation frequencies in order to establish if a function can or cannot be used to annotate a certain species. The tool generates constraints between GO terms and taxa and then propagates these relations over the taxonomic tree and the GO graph. Since these constraints nearly cover the whole taxonomy, it is possible to obtain the mapping of a function over the taxonomy. FunTaxIS can be used to make functional comparative analyses among taxa, to detect improper associations between taxa and functions, and to discover how functional knowledge is either distributed or missing. A benchmark test set based on six different model species has been devised to get useful insights on the generated taxonomic rules

Tensions in the strategic integration of corporate sustainability through global standards:Evidence from Japan and South Korea

International audienceDespite the importance of the conflicting dimensions of corporate sustainability for business strategy, little is known about the tensions that derive from adopting global environmental and social standards in East Asia. Through 65 in-depth interviews conducted in Tokyo and Seoul, this article examines the tensions—and reactions to these tensions—of corporate sustainability managers tasked with the implementation of such standards in Japanese and South Korean multinational corporations. These represent key contexts of inquiry because of their normative tradition of corporate sustainability and geographical closeness. While elucidating that corporate sustainability managers in both countries encounter societal-commercial, traditional-modern, and individual-collective tensions, the article describes the ways they react differently to these tensions. This article contributes to the literature on corporate sustainability and tensions and the contextual literature on corporate sustainability in Japan and South Korea, ultimately offering takeaways for the strategic planning of multinational corporations

Classical surrogate simulation of quantum systems with LOWESA

We introduce LOWESA as a classical algorithm for faithfully simulating quantum systems via a classically constructed surrogate expectation landscape. After an initial overhead to build the surrogate landscape, one can rapidly study entire families of Hamiltonians, initial states and target observables. As a case study, we simulate the 127-qubit transverse-field Ising quantum system on a heavy-hexagon lattice with up to 20 Trotter steps which was recently presented in Nature 618, 500-505 (2023). Specifically, we approximately reconstruct (in minutes to hours on a laptop) the entire expectation landscape spanned by the heavy-hex Ising model. The expectation of a given observable can then be evaluated at different parameter values, i.e. with different onsite magnetic fields and coupling strengths, in fractions of a second on a laptop. This highlights that LOWESA can attain state-of-the-art performance in quantum simulation tasks, with the potential to become the algorithm of choice for scanning a wide range of systems quickly.Comment: 13 pages, 6 figure

Contesting corporate responsibility in the Bangladesh garment industry: the local factory owner perspective

In the developing economy of Bangladesh, local factory owners in the garment industry have felt great pressure to improve factory safety, but the costs for those improvements are not shared by the global apparel firms that wield immense influence over them. Consequently, we examine whether multi-stakeholder initiatives (MSIs), as vehicles of corporate social responsibility (CSR), offer platforms for democratic oversight or merely serve as new arenas to exercise corporate power. Given their role in connecting global and local contexts and their history of safety incidents, local factory owners possess a unique perspective on the impact and contested nature of CSR in global supply chains. This article presents a qualitative study of MSIs in the Bangladesh garment industry, particularly after the Rana Plaza collapse. Through interviews with local factory owners and executive managers, we explore the reasons behind their opposition to CSR as exercised by global apparel firms, and the contestation of those practices by their local business association. Our findings lead us to conclude that garment industry MSIs are unlikely to be effective without labor procurement practices that harmonize global and local interests to mitigate the competitive pressures on local factory owners.The authors received no financial support for the research, authorship, and/or publication of this article

Connecting the Hamiltonian structure to the QAOA energy and Fourier landscape structure

In this paper, we aim to expand the understanding of the relationship between the composition of the Hamiltonian in the Quantum Approximate Optimization Algorithm (QAOA) and the corresponding cost landscape characteristics. QAOA is a prominent example of a Variational Quantum Algorithm (VQA), which is most commonly used for combinatorial optimization. The success of QAOA heavily relies on parameter optimization, which is a great challenge, especially on scarce noisy quantum hardware. Thus understanding the cost function landscape can aid in designing better optimization heuristics and therefore potentially provide eventual value. We consider the case of 1-layer QAOA for Hamiltonians with up to 5-local terms and up to 20 qubits. In addition to visualizing the cost landscapes, we calculate their Fourier transform to study the relationship with the structure of the Hamiltonians from a complementary perspective. Furthermore, we introduce metrics to quantify the roughness of the landscape, which provide valuable insights into the nature of high-dimensional parametrized landscapes. While these techniques allow us to elucidate the role of Hamiltonian structure, order of the terms and their coefficients on the roughness of the optimization landscape, we also find that predicting the intricate landscapes of VQAs from first principles is very challenging and unlikely to be feasible in general

Different distribution patterns of hoverflies (Diptera: Syrphidae) and bees (Hymenoptera: Anthophila) along altitudinal gradients in Dolomiti Bellunesi National Park (Italy)

Hoverflies (Diptera: Syrphidae) and bees (Hymenoptera: Anthophila) are two key taxa for plant pollination. In the present research, the altitudinal distribution of these taxa was studied along two gradients (elevation range: 780–2130 m) in the Dolomiti Bellunesi National Park (Northeastern Italy). Pan traps were used as a sampling device to collect both hoverflies and bees. Other than altitude, the effect of landscape complexity and plant diversity were considered as potential predictors of hoverfly and bee richness and abundance along the two gradients. A total of 68 species of hoverflies and 67 of bees were collected during one sampling year, confirming the efficacy of pan traps as a sampling device to study these taxa. Altitude was the main variable affecting both hoverfly and bee distribution. The two taxa show different distribution patterns: hoverflies have a unimodal distribution (richness and abundance) with peak at middle altitude (1500 m), while bees have a monotonic decline (richness and abundance) with increasing altitude. Both hoverfly and bee populations change with the increasing altitude, but the change in hoverflies is more pronounced than in bees. Species turnover dominates the β-diversity both for hoverflies and bees; therefore, the hoverfly and bee communities at higher altitudes are not subsamples of species at lower altitude but are characterized by different species. This poses important conservation consequences. Some rare species, typical of an alpine habitat were recorded; the present research represents important baseline data to plan a monitoring scheme aimed at evaluating the effect of climate change on pollinators in these fragile habitat

Evaluating the noise resilience of variational quantum algorithms

We simulate the effects of different types of noise in state preparation circuits of variational quantum algorithms. We first use a variational quantum eigensolver to find the ground state of a Hamiltonian in presence of noise, and adopt two quality measures in addition to the energy, namely fidelity and concurrence. We then extend the task to the one of constructing, with a layered quantum circuit ansatz, a set of general random target states. We determine the optimal circuit depth for different types and levels of noise, and observe that the variational algorithms mitigate the effects of noise by adapting the optimised parameters. We find that the inclusion of redundant parameterised gates makes the quantum circuits more resilient to noise. For such overparameterised circuits different sets of parameters can result in the same final state in the noiseless case, which we denote as parameter degeneracy. Numerically, we show that this degeneracy can be lifted in the presence of noise, with some states being significantly more resilient to noise than others. We also show that the average deviation from the target state is linear in the noise level, as long as this is small compared to a circuit-dependent threshold. In this region the deviation is well described by a stochastic model. Above the threshold, the optimisation can converge to states with largely different physical properties from the true target state, so that for practical applications it is critical to ensure that noise levels are below this threshold.Comment: 22 pages, 13 figure

Optimizing parametrized quantum circuits via noise-induced breaking of symmetries

Very little is known about the cost landscape for parametrized Quantum Circuits (PQCs). Nevertheless, PQCs are employed in Quantum Neural Networks and Variational Quantum Algorithms, which may allow for near-term quantum advantage. Such applications require good optimizers to train PQCs. Recent works have focused on quantum-aware optimizers specifically tailored for PQCs. However, ignorance of the cost landscape could hinder progress towards such optimizers. In this work, we analytically prove two results for PQCs: (1) We find an exponentially large symmetry in PQCs, yielding an exponentially large degeneracy of the minima in the cost landscape. (2) We show that noise (specifically non-unital noise) can break these symmetries and lift the degeneracy of minima, making many of them local minima instead of global minima. Based on these results, we introduce an optimization method called Symmetry-based Minima Hopping (SYMH), which exploits the underlying symmetries in PQCs to hop between local minima in the cost landscape. The versatility of SYMH allows it to be combined with local optimizers (e.g., gradient descent) with minimal overhead. Our numerical simulations show that SYMH improves the overall optimizer performance.Comment: 11 + 5 pages, 10 figure

New Eriophyoid mites (Acari Eriophyoidea) from Italy. II

Three new eriophyoid species, collected in Veneto (Northern Italy), are described and illustrated also using scanning electron microscopy. Aceria biradiatus n. sp. was found vagrant on Corylus avellana L. (Fam. Corylaceae). Cecidophyes campestris n. sp. was collected on Acer campestre L. and A. pseudoplatanus L. (Fam. Aceraceae); it was associated to a hypertrichosis on the leaves of A. campestre at the level of the nervature ramifications. Diptacus corni n. sp. was vagrant on Cornus sanguinea L. (Fam. Corneaceae). Key words: hedges, phytophagous, alternative prey.ACARI ERIOFIOIDEI (ACARI ERIOPHYOIDEA) NUOVI PER L’ITALIA. II Tre nuove specie di eriofioidei, raccolte in Veneto, sono descritte e illustrate anche mediante l’utilizzazione del microscopio elettronico a scansione. Aceria biradiatus sp. n. è stato raccolto vagante su foglie di Corylus avellana L. (Fam. Corylaceae). Cecidophyes campestris sp. n. è stato rinvenuto su Acer campestre L. e A. pseudoplatanus L. (Aceraceae); le foglie infestate di acero campestre presentavano una leggera ipertricosi presso la biforcazione delle nervature. Diptacus corni sp. n. è stato osservato vagante su Cornus sanguinea L. (Fam. Corneaceae). Parole chiave: siepi, fitofagi, prede alternative.