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The megalithic pillar sites found around Lake Turkana, Kenya, are monumental cemeteries built approximately 5000 years ago. Their construction coincides with the spread of pastoralism into the region during a period of profound climate change. Early work at the Jarigole pillar site suggested that these places were secondary burial grounds. Subsequent excavations at other pillar sites, however, have revealed planned mortuary cavities for predominantly primary burials, challenging the idea that all pillar sites belonged to a single 'Jarigole mortuary tradition'. Here, the authors report new findings from the Jarigole site that resolve long-standing questions about eastern Africa's earliest monuments and provide insight into the social lives, and deaths, of the region's first pastoralists. Keywords: Eastern Africa, megalithic architecture, funerary archaeology, mortuary practices, pastoralist society, Introduction The earliest evidence of monumentality in eastern Africa coincides with the initial spread of food production into sub-Saharan Africa during a period of profound climatic, economic and social change [...]

Common assumptions about the ephemeral archaeological signature of pastoralist settlements have limited the application of geophysical techniques in the investigation of past herding societies. Here, the authors present a geophysical survey of Luxmanda, Tanzania, the largest-known settlement documented for the Pastoral Neolithic era in eastern Africa (,c. 5000-1200 BP). The results demonstrate the value and potential of fluxgate gradiometry for the identification of magnetic anomalies relating to archaeological features, at a category of site where evidence for habitation was long thought to be undetectable. The study provides comparative data to enable archaeologists to identify loci for future investigations of mobile populations in eastern Africa and elsewhere. Keywords: Africa, Tanzania, geophysical survey, pastoralism, mobility, Introduction Archaeologists worldwide are now applying geochemical, biomolecular and ethnoarchaeological approaches to understand the long-term social and environmental histories of ancient pastoralism (Honeychurch & Makarewicz 2016). Common early assumptions held [...]

Using the Central Andean Chavín Phenomenon as a case study, this paper explores the middle ground between top-down (big data) and bottom-up (Bayesian modeling) approaches to archaeological radiocarbon data. Compiling radiocarbon dates associated with the Chavín Phenomenon addresses questions of chronology, demonstrating that the relevant phases at interacting sites are relatively brief and broadly contemporary. In addition, the definition of a discrete span of time associated with the Chavín Phenomenon makes it possible to explore the context for that period of heightened interaction. Juxtaposing that timespan with a compilation of Central Andean radiocarbon dates identifies contemporary non-participatory sites, enabling characterization of the sociopolitical milieu within which the Chavín Phenomenon emerged, flourished, and faded. The identification of that corpus of sites also highlights the importance of a shift in focus from identification of interaction to characterization of interaction. Bottom-up approaches to radiocarbon chronology will be a key element of that effort, while high-level summary of radiocarbon assemblages can identify where additional dating and Bayesian modeling can have the greatest interpretive impact. [ABSTRACT FROM AUTHOR]

Unique worldwide, nitrate/iodine deposits (NIDs) are located along a 700 km geological belt in the Atacama Desert, Chile. They serve as the primary source of mineral ores for the extraction of iodine, sodium, and potassium nitrates. NIDs have been relatively underexplored from a biological perspective. To address this, we collected sixteen soil samples from abandoned mines in Oficinas Pissis and Savona for chemical, mineralogical, and metagenomic analyses. The soils primarily consisted of halite and darapskite, with only one sample being predominantly composed of thenardite. Deliquescence and water activity measurements yielded values ranging from 0.02% to 0.40% and 0.47 to 0.62, respectively. To investigate the presence, identification, relative abundance, and diversity of microbial life in NID soils, we employed MiSeq high-throughput sequencing and bioinformatic tools. The dominant phyla observed were Firmicutes and Proteobacteria, with Actinobacteria and Cyanobacteria being predominant in two soil samples. Furthermore, we detected nitrate/perchlorate-reducing bacterial activity in enriched cultures from the soil samples. This study sheds light on the resilience of microbial life in the Atacama Desert NIDs, providing compelling evidence for its existence and offering insight into factors that could facilitate it within this unique environment. [ABSTRACT FROM AUTHOR]

Featured Application: Navigation of autonomous agents without a source of complete and global knowledge of the environment, such as Global Positioning Systems. When autonomous agents are deployed in an unknown environment, obstacle-avoiding movement and navigation are required basic skills, all the more so when agents are limited by partial-observability constraints. This paper addresses the problem of autonomous agent navigation under partial-observability constraints by using a novel approach: Artificial Potential Fields (APF) assisted by heuristics. The well-known problem of local minima is addressed by providing the agents with the ability to make individual choices that can be exploited in a swarm. We propose a new potential function, which provides precise control of the potential field's reach and intensity, and the use of auxiliary heuristics provides temporary target points while the agent explores, in search of the position of the real intended target. Artificial Potential Fields, together with auxiliary search heuristics, are integrated into a novel navigation model for autonomous agents who have limited or no knowledge of their environment. Experimental results are shown in 2D scenarios that pose challenging situations with multiple obstacles, local minima conditions and partial-observability constraints, clearly showing that an agent driven using the proposed model is capable of completing the navigation task, even under the partial-observability constraints. [ABSTRACT FROM AUTHOR]

This paper is based on a multiple case study of schools which have been identified as improving their performance for about a decade. We proposed different criteria by which to characterize and study these improvement processes and, by applying them to our sample, we elaborated a typology of school improvement trajectories: we identified 4 different trajectories of school improvement. We called the first type "restricted improvement" because at its center is the management of processes that mainly target academic achievement tests; the second is "incipient improvement," which is based on changes that restructure the school processes; the third identified trajectory are cases where school improvement is "moving toward institutionalization," while the last are those cases where improvement has been already "institutionalized" and the schools have achieved high levels of educational effectiveness. We identified challenges that schools face at different stages of school improvement and discussed some related policy issues.

Con el objetivo de analizar la relación entre turismo culinario y patrimonio histórico se desarrolló un estudio de caso con enfoque cualitativo, que aborda el análisis de una comunidad productora de una sal milenaria en el centro de México. Las categorías de análisis fueron los actores sociales, el producto alimentario y el territorio. Los resultados muestran que la actividad turística presenta efectos ambivalentes hacia la reproducción social de un bien patrimonial alimentario con fuertes vínculos históricos. Se concluye que es necesaria una revisión de los retos y oportunidades que enfrenta el campo mexicano frente a la inserción del turismo rural como una estrategia de desarrollo.

Introduction: Current guidelines recommend that patients with cerebral venous thrombosis (CVT) should be treated with vitamin K antagonists (VKAs) for 3-12 months. Direct oral anticoagulants (DOACs), however, are increasingly used in clinical practice. An exploratory randomized controlled trial including 120 patients with CVT suggested that the efficacy and safety profile of dabigatran (a DOAC) is similar to VKAs for the treatment of CVT, but large-scale prospective studies from a real-world setting are lacking. Methods: DOAC-CVT is an international, prospective, observational cohort study comparing DOACs to VKAs for the prevention of recurrent venous thrombotic events after acute CVT. Patients are eligible if they are 18 years or older, have a radiologically confirmed CVT, and have started oral anticoagulant treatment (DOAC or VKA) within 30 days of CVT diagnosis. Patients with an absolute contra-indication for DOACs, such as pregnancy or severe renal insufficiency, are excluded from the study. We aim to recruit at least 500 patients within a three-year recruitment period. The primary endpoint is a composite of recurrent venous thrombosis and major bleeding at 6 months of follow-up. We will calculate an adjusted odds ratio for the primary endpoint using propensity score inverse probability treatment weighting. Discussion: DOAC-CVT will provide real-world data on the comparative efficacy and safety of DOACs versus VKAs for the treatment of CVT. [ABSTRACT FROM AUTHOR]

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South American arid lands present unique constellations of climatic risk to their human inhabitants, due to volatile events that can create markedly different hydroclimate conditions over interannual–centennial scales. However, a main driver of such volatility – the El Niño/Southern Oscillation (ENSO) – occurs with semiregular periodicity. Paleoclimatic and archeological evidence indicate not only that the strength and periodicity of ENSO patterns have changed over the late-Holocene, but their impacts were likely recognized, adapted to, and perhaps capitalized upon by agriculturalists employing adaptive risk strategies. We examine relationships over the last 1.3 kyr between ENSO periodicity, ecological transitions, and archeological settlement in Peru's Chicama Valley through a coupled paleohydroclimate and agroecology model. We reconstruct periods when ENSO-like conditions dominated past hydroclimates and present a quantitative, spatially-explicit analysis of ecological productivity during modern ENSO-positive hydroclimate conditions. We show that archeological settlement patterns are sensitive to these transformations and reflect efforts to capitalize on expanded agroecological niches. Such expanded niches potentially offset the adverse impacts and risks associated with abrupt ENSO climate events. These results suggest archeological communities were aware of ENSO risk and managed productive strategies accordingly, highlighting the importance of a risk calculus that considers the net ecological effects of climate events. [ABSTRACT FROM AUTHOR]

This work presents a behavioral model for a microelectromechanical (MEM) relay for use in circuit simulation. Models require calibration, and other published relay models require over a dozen parameters for calibration, many of which are difficult to extract or are only available after finite element analysis. This model improves on prior work by taking advantage of model normalization, which often results in models that require fewer parameters than un-normalized models. This model only needs three parameters extracted from experiment and one dimension known from device fabrication to represent its non-contact behavior, and two additional extracted parameters to represent its behavior when in contact. The extracted parameters–quality factor, resonant frequency, and the pull-in voltage–can be found using laser Doppler vibrometry. The device dimension is the actuation gap size, which comes from process data. To demonstrate this extraction process, a series of velocity step responses were excited in MEM relays, the measured velocity responses were used to calibrate the model, and then then simulations of the model (implemented in Verilog-A) were compared against the measured data. The error in the simulated oscillation frequency and peak velocity, two values selected as figures of merit, is less than 10% across many operating voltages. [ABSTRACT FROM AUTHOR]

Iron-limited cyanobacterial cells are generally considered to acquire extracellular iron through a siderophore-dependent system, although evidence has started to accumulate that other, as yet poorly characterized, iron acquisition systems may also play a role. Iron-limited cells of the cyanobacterium Anabaena flos-aquae (Lyng.) Breb. are well known to produce the relatively low Fe(III) affinity dihydroxamate siderophore schizokinen. In this set of experiments we show that iron-limited A. flos-aquae cells (i) acquired iron at substantial rates in the absence of the schizokinen and (ii) acquired iron from a bacterial siderophore (the trihydroxamate molecule desferrioxamine B (DFB)), and also a synthetic chelator (N, N-bis(2-(bis(carboxymethyl)amino)ethyl)glycine (DTPA)), with substantially higher affinities for Fe(III) than schizokinen, indicating that a schizokinen-independent iron acquisition pathway was operating. We suggest that there exists a siderophoreindependent iron acquisition system that is able to acquire Fe(III) from high stability Fe(III)-chelates, which are not accessible to iron-limited cells via the schizokinen-based system. As well, we present two possible models for iron acquisition by iron-limited A. flos-aquae cells. Both of these models suggest that there are two major routes for Fe(III) entry into the periplasm of iron-limited cells: (1) the well-characterized siderophore (schizokinen) dependent process and (2) a siderophore-independent process that is able to access Fe(III) sources not biologically available to the schizokinen system. Key words: Anabaena, cyanobacteria, iron limitation, iron uptake, outer membrane, schizokinen, siderophores, siderophoreindependent. On considere generalement que les cellules cyanobacteriennes limitees par le fer acquierent du fer extracellulaire par un systeme dependant de siderophores, bien que la preuve commence a s'accumuler a l'effet que d'autres systemes d'acquisition du fer encore peu documentes puissent egalement jouer un role. On sait tres bien que les cellules de la cyanobacterie Anabaena flos-aquae (Lyng.) Breb. limitees par le fer, produisent la schizochinene sous forme de siderophore a dihydroxamate a relativement faible affinite pour le Fe(III). Dans cet ensemble d'experiences, les auteurs montrent que les cellules de l'A. flos-aquae limitees par le fer (i) acquierent du fer a des taux substantiels en absence de la schizochinene, et (ii) acquierent du fer a partir d' un siderophore bacterien (la molecule trihydroxamate desferrioxamine B (DFB), et aussi d' un chelateur synthetique (N,N-bis(2-(bis(carboxymethyl)amino)ethyl) glycine (DTPA)), ayant une affinite substantielle plus forte pour le Fe(III) que pour la schizokinene, indiquant qu' un sentier d' acquisition du fer independante de la schizochinene est intervenu. Les auteurs suggerent qu'il existe un systeme d'acquisition du fer independant, capable d'acquerir le Fe(III) a partir de chelates de Fe(III) a haute stabilite N'etant pas accessible aux cellules via le systeme base sur la schizochinene. De plus, les auteurs presentent deux modeles possibles pour l'acquisition du fer par les cellules de l'A. flos-aquae. Les deux modeles suggerent qu'il y aurait deux routes principales pour permettre l'entree du Fe(III) dans le periplasme des cellules limitees par le fer : (1) le processus bien caracterise du processus dependant d'un siderophore (Schizokinene) et (2) un processus independant du siderophore capable d'acceder a des sources de Fe(III) non biologiquement accessibles au systeme impliquant la schizokinene. Mots-cles : Anabaena, cyanobacterie, limitation par le fer, absorption du fer, membrane externe, schizokinene, siderophore, independant de siderophores. [Traduit par la Redaction], Introduction Iron is an essential element for almost all organisms and photosynthetic organisms have an especially high iron requirement, mainly owing to the high iron content of the photosynthetic apparatus. [...]

This article presents a new initiative in combating looting from the air, building on previous work in Iraq and Jordan. Looted sites in the Viru Valley, Peru, are visible as pit clusters on dated versions of Google Earth. Compare these with earlier air photographs and Gordon Willey's famous survey of the 1940s, and we have a dated chronicle of looting events. This makes it possible to demonstrate that modern looting is certainly taking place and linked to an upsurge in the antiquities trade. As well as being a new instrument for managing heritage, the author shows that the looting survey offers an important research dividend: the location of cemeteries not previously systematically documented, with potential for more thorough investigation even of already looted areas. Keywords: Peru, Viru, looting, aerial survey, Google Earth, Introduction Archaeologists, conservationists, and a variety of other stakeholders, now recognise the market-driven looting of archaeological sites as a global problem, but solutions remain elusive and even describing the problem [...]

Human beings are an active component of every terrestrial ecosystem on Earth. Although our local impact on the evolution of these ecosystems has been undeniable and extensively documented, it remains unclear precisely how our activities are altering them, in part because ecosystems are dynamic systems structured by complex, non-linear feedback processes and cascading effects. We argue that it is only by studying human–environment interactions over timescales that greatly exceed the lifespan of any individual human (i.e., the deep past or longue durée), we can hope to fully understand such processes and their implications. In this article, we identify some of the key challenges faced in integrating long-term datasets with those of other areas of sustainability science, and suggest some useful ways forward. Specifically, we (a) highlight the potential of the historical sciences for sustainability science, (b) stress the need to integrate theoretical frameworks wherein humans are seen as inherently entangled with the environment, and (c) propose formal computational modelling as the ideal platform to overcome the challenges of transdisciplinary work across large, and multiple, geographical and temporal scales. Our goal is to provide a manifesto for an integrated scientific approach to the study of socio-ecological systems over the long term. [ABSTRACT FROM AUTHOR]

This work discusses the electrical break down of tungsten oxide films that form on contacting surfaces of tungsten electrodes in micro-electro-mechanical (MEM) relays. Electrical tests were applied to the contacts of 27 devices to measure the voltage, current and charge required to break down the oxide films, and also to measure the change in current through the contacts as the film healed. The oxide breaks down when an average of 58 $\mu \text{C}$ of electronic charge passes through the oxide, which usually requires applying 1–2 V to drive 100 nA- $10~\mu \text{A}$ of current through the contact. The tungsten oxide heals quickly in laboratory ambient conditions: applying 0.5 V to a contact immediately after breaking down an oxide results in a contact current greater than $5~\mu \text{A}$ , but the same test only induces 1 nA of current 1–5 minutes later. The reduction in contact current with time follows a power law, which is characteristic of charge relaxation in oxides. Additionally, Holm’s experiment shows that current conduction through the contacts is dominated by tunneling through an oxide. These facts together suggest that the break down and healing are electrical processes related to trap accumulation and relaxation in the tungsten oxide. [2021-0161] [ABSTRACT FROM AUTHOR]