Comment on 'Helmholtz theorem and the v-gauge in the problem of superluminal and instantaneous signals in classical electrodynamics,' by Chubykalo et al [Found. of Phys. Lett, 19, 37-46 (2006)]

Fundamental errors in the Chubykalo et al paper [Found. of Phys. Lett, 19, 37-46 (2006)] are highlighted. Contrary to their claim that "... the irrotational component of the electric field has a physical meaning and can propagate exclusively instantaneously," it is shown that this instantaneous component is physically irrelevant because it is always canceled by a term contained into the solenoidal component. This result follows directly from the solution of the wave equation that satisfies the solenoidal component. Therefore the subsequent inference of these authors that there are two mechanisms of transmission of energy and momentum in classical electrodynamics, one retarded and the other one instantaneous, has no basis. The example given by these authors in which the full electric field of an oscillating charge equals its instantaneous irrotational component on the axis of oscillations is proved to be false.Comment: An alternative discussion can be found in the paper: Jose A. Heras, "How potentials in different gauges yield the same retarded electric and magnetic fields," Am. J. Phys. 75, 176-183 (2007

Comment on 'A generalized Helmholtz theorem for time-varying vector fields by A. M. Davis, [Am. J. Phys. 74, 72-76 (2006)]'

In a recent paper Davis formulated a generalized Helmholtz theorem for a time-varying vector field in terms of the Lorenz gauge retarded potentials. The purposes of this comment are to point out that Davis's generalization of the theorem is a version of the extension of the Helmholtz theorem formulated some years ago by McQuistan and also by Jefimenko and more recently by the present author and to show that Davis's expression for the time-dependent vector field is also valid for potentials in gauges other than the Lorenz gau

Can Maxwell's equations be obtained from the continuity equation?

We formulate an existence theorem that states that given localized scalar and vector time-dependent sources satisfying the continuity equation, there exist two retarded fields that satisfy a set of four field equations. If the theorem is applied to the usual electromagnetic charge and current densities, the retarded fields are identified with the electric and magnetic fields and the associated field equations with Maxwell's equations. This application of the theorem suggests that charge conservation can be considered to be the fundamental assumption underlying Maxwell's equations.Comment: 14 pages. See the comment: "O. D. Jefimenko, Causal equations for electric and magnetic fields and Maxwell's equations: comment on a paper by Heras [Am. J. Phys. 76, 101 (2008)].

Accelerated Extinction Profiles for Anomaly Detection in Fluvial Ecosystems

New multispectral sensors, which are capable of capturing high resolution images through low altitude drone flights, offer access to a wealth of information about the Earth's surface at a significantly lower cost than other imaging devices. The process of identifying unexpected patterns within an image that do not conform to the expected behavior is known as anomaly detection (AD). When applied to fluvial ecosystem monitoring, this involves detecting the existence of small constructions or roads that allow automatic alarms to be produced for the people in charge of monitoring the ecosystem. The extraction of spatial information is a critical step in AD, since it determines the final quality of the AD and it is a computationally expensive processing. In this work, Extinction Profiles (EP) are selected to perform a multilevel implicit segmentation of the image, thus extracting the spatial information of relevance. A computationally efficient implementation of the EP-based spatial extraction of information for multidimensional images is proposed in this paper, as it is a basic step in the detection of anomalies in natural ecosystems. The proposed method takes advantage of heterogeneous computing to perform the task in a reduced execution time.This work was supported in part by grants PID2019--104834GB--I00, PID2022-141623NB-I00, and TED2021--130367B--I00 funded by MCIN/AEI/10.13039/501100011033 and by European Union NextGenerationEU/PRTR. It was also supported by Xunta de Galicia - Consellería de Cultura, Educación, Formación Profesional e Universidades [Centro de investigación de Galicia accreditation 2019-2022 ED431G-2019/04 and Reference Competitive Group accreditation, ED431C-2022/16], by Junta de Castilla y León [Project VA226P20 (PROPHET--II)], and by European Regional Development Fund (ERDF)

Hipster: Integrating Theory Exploration in a Proof Assistant

This paper describes Hipster, a system integrating theory exploration with the proof assistant Isabelle/HOL. Theory exploration is a technique for automatically discovering new interesting lemmas in a given theory development. Hipster can be used in two main modes. The first is exploratory mode, used for automatically generating basic lemmas about a given set of datatypes and functions in a new theory development. The second is proof mode, used in a particular proof attempt, trying to discover the missing lemmas which would allow the current goal to be proved. Hipster's proof mode complements and boosts existing proof automation techniques that rely on automatically selecting existing lemmas, by inventing new lemmas that need induction to be proved. We show example uses of both modes

Ingested insecticide to control Aedes aegypti: developing a novel dried attractive toxic sugar bait device for intra-domiciliary control

© 2020 The Author(s). Background: Illnesses transmitted by Aedes aegypti (Linnaeus, 1762) such as dengue, chikungunya and Zika comprise a considerable global burden; mosquito control is the primary public health tool to reduce disease transmission. Current interventions are inadequate and insecticide resistance threatens the effectiveness of these options. Dried attractive bait stations (DABS) are a novel mechanism to deliver insecticide to Ae. aegypti. The DABS are a high-contrast 28 inch2 surface coated with dried sugar-boric acid solution. Aedes aegypti are attracted to DABS by visual cues only, and the dried sugar solution elicits an ingestion response from Ae. aegypti landing on the surface. The study presents the development of the DABS and tests of their impact on Ae. aegypti mortality in the laboratory and a series of semi-field trials. Methods: We conducted multiple series of laboratory and semi-field trials to assess the survivability of Ae. aegypti mosquitoes exposed to the DABS. In the laboratory experiments, we assessed the lethality, the killing mechanism, and the shelf life of the device through controlled experiments. In the semi-field trials, we released laboratory-reared female Ae. aegypti into experimental houses typical of peri-urban tropical communities in South America in three trial series with six replicates each. Laboratory experiments were conducted in Quito, Ecuador, and semi-field experiments were conducted in Machala, Ecuador, an area with abundant wild populations of Ae. aegypti and endemic arboviral transmission. Results: In the laboratory, complete lethality was observed after 48 hours regardless of physiological status of the mosquito. The killing mechanism was determined to be through ingestion, as the boric acid disrupted the gut of the mosquito. In experimental houses, total mosquito mortality was greater in the treatment house for all series of experiments (P \u3c 0.0001). Conclusions: The DABS devices were effective at killing female Ae. aegypti under a variety of laboratory and semi-field conditions. DABS are a promising intervention for interdomiciliary control of Ae. aegypti and arboviral disease prevention.[Figure not available: see fulltext.

Rethinking preventive conservation: recent examples

The past few decades have seen an increasing awareness of the potential socioeconomical and environmental impact of investment in Cultural Heritage (CH). Preserving CH is not only an obligation to sustain and transmit it to the future generation but is also a driver of sustainable growth. Here, recently concluded projects are taken in consideration for a reflective thinking on preventive conservation, as the only viable strategy towards a sustainable and cost-effective management of CH, to face unprecedented challenges posed by increasing natural and man-made threats. Here, the main open issues for a widespread implementation of preventive conservation are identified, moreover, standardised, integrated good practices, validated over significant case studies, are presented within a multi-level replicable framework.This work was financed by ERDF funds through the V Interreg Sudoe program within the framework of the project “HeritageCare - Monitoring and preventive conservation of historic and cultural heritage” (Ref. SOE1/P5/P0258). The Heritage Within research project was co-funded by the Creative Europe Programme of the European Union, under the Cross-sectorial subprogramme, Bridging culture and audiovisual content through digital action (Project 614719-CREA-1-2019-1-PT-CROSS-SECT-INNOVLAB). Moreover, this work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020

Seismic behaviour assessment of vernacular isolated buildings

This paper presents the numerical seismic analysis of isolated vernacular buildings characteristic of the Alentejo region, which is considered a medium seismic hazard region in Portugal.A representative isolated building was selected from a database, and a geometric model was defined for the numerical pushover analysis. Subsequently, a parametric analysis was carried out to assess the influence of distinct parameters on the seismic behaviour of such buildings.(undefined

Seismic vulnerability of vernacular buildings in urban centres: the case of Vila Real de Santo António

Following detailed studies of Portuguese vernacular building typologies, this paper deals with buildings located in historical urban centres. An analysis of the history of the urban centre and, in particular, of some vernacular buildings is enhanced. Additionally, a discussion on the influence of changes of the geometry, and on added built volumes to original buildings in the seismic vulnerability of the buildings is also provided.(undefined

Relational job crafting: Exploring the role of employee motives with a weekly diary study

© The Author(s) 2018. In this weekly diary study, we integrated research on job crafting to explore the associations between expansion and contraction oriented relational job crafting, work engagement and manager-rated employee behaviours (work performance and voice). Furthermore, we investigated cross-level moderations of prosocial and impression management motives on our proposed associations. We tested our hypotheses with matched data collected over seven weeks in Istanbul, Turkey. The results from multilevel analyses revealed that (a) expansion oriented relational job crafting is positively related with work performance and voice via work engagement, while (b) contraction oriented relational job crafting is negatively related with work performance and voice via work engagement, all measured at the week level. Furthermore, impression management motives of employees moderated the association between expansion oriented relational job crafting and work engagement in that this positive association is stronger for employees low on impression management motives. Our results contribute to job crafting research in two ways. First, it focuses on relational job crafting and discusses how and why the two opposite types of relational job crafting (expansion versus contraction oriented) impact on work engagement and employees’ key outcomes in the way they do. This addresses the question ‘is there a dark side to job crafting?’ Second, it focuses on the importance of context and integrates two motives relevant to understand how relational job crafting unfolds, thereby taking a step to address questions for whom (i.e. what kinds of employees), relational job crafting is more effective and translates into enhanced (vs deteriorated) work outcomes. Moreover, our use of a weekly within-person design adds to a recently growing research stream emphasizing the dynamic nature of job crafting