JURNAL AGROTEKNOLOGI
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Pigeons retain partial memories of homing paths years after learning them individually, collectively or culturally
No full textMemory of past experience is central to many animal decisions, but how long specific memories can
influence behaviour is poorly understood. Few studies have reported memories retrieved after
several years in non-human animals, especially for spatial tasks, and whether the social context
during learning could affect long-term memory retention. We investigated homing pigeons’ spatial
memory by GPS-recording their homing paths from a site 9 km from their loft. We compared solo
flights of naïve pigeons with those of pigeons that had last homed from this site 3 to 4 years earlier,
having learnt a homing route either alone (“individual learning”), together with a naïve partner
(“collective learning”) or within cultural transmission chains (“cultural learning”). We used as a
control a second release site unfamiliar to all pigeons. Pigeons from all learning treatments
outperformed naïve birds at the familiar (but not the unfamiliar) site, but the idiosyncratic routes
they formerly used several years before were now partially forgotten. Our results show that nonhuman animals can use their memory to solve a spatial task years after they last performed it,
irrespective of the social context during learning. They also suggest that without reinforcement,
landmarks and culturally acquired “route traditions” are gradually forgotten
Young children share more under time pressure than after a delay
No full textAdults under time pressure share with others generously, but with more time they act more selfishly. In the current study, we investigated whether young children already operate in this same way, and, if so, whether this changes over the preschool and early school age years. We tested 144 children in three age groups (3-, 5-, and 7-year olds) in a one-shot dictator game: Children were given nine stickers and had the possibility to share stickers with another child who was absent. Children in the Time Pressure condition were instructed to share quickly, whereas children in the Delay condition were instructed to take time and consider their decision carefully. Across ages, children in the Time Pressure condition shared significantly more stickers than children in the Delay condition. Moreover, the longer children waited, the less they shared. Thus, children, like adults, are more prosocial when acting spontaneously than after considering their decision more carefully
Clocks, viruses, and immunity: lessons for the COVID-19 Pandemic
No full textCircadian rhythms are evolutionarily conserved anticipatory systems that allow the host to prepare and respond to threats in its environment. This article summarizes a European Biological Rhythms Society (EBRS) workshop held in July 2020 to review current knowledge of the interplay between the circadian clock and viral infections to inform therapeutic strategies against SARS-CoV-2 and COVID-19. A large body of work supports the role of the circadian clock in regulating various aspects of viral replication, host responses, and associated pathogenesis. We review the evidence describing the multifaceted role of the circadian clock, spanning host susceptibility, antiviral mechanisms, and host resilience. Finally, we define the most pressing research questions and how our knowledge of chronobiology can inform key translational research priorities
Online k-means clustering
No full textWe study the problem of learning a clustering of an online set of points. The specific formulation we use is the k-means objective: At each time step the algorithm has to maintain a set of k candidate centers and the loss incurred by the algorithm is the squared distance between the new point and the closest center. The goal is to minimize regret with respect to the best solution to the k-means objective in hindsight. We show that provided the data lies in a bounded region, learning is possible, namely an implementation of the Multiplicative Weights Update Algorithm (MWUA) using a discretized grid achieves a regret bound of O~(T−−√) in expectation. We also present an online-to-offline reduction that shows that an efficient no-regret online algorithm (despite being allowed to choose a different set of candidate centres at each round) implies an offline efficient algorithm for the k-means problem, which is known to be NP-hard. In light of this hardness, we consider the slightly weaker requirement of comparing regret with respect to (1+ϵ)OPT and present a no-regret algorithm with runtime O(Tpoly(log(T),k,d,1/ϵ)O(kd)). Our algorithm is based on maintaining a set of points of bounded size which is a coreset that helps identifying the \emph{relevant} regions of the space for running an adaptive, more efficient, variant of the MWUA. We show that simpler online algorithms, such as \emph{Follow The Leader} (FTL), fail to produce sublinear regret in the worst case. We also report preliminary experiments with synthetic and real-world data. Our theoretical results answer an open question of Dasgupta (2008)
The noisy silence of Gukurahundi: truth, recognition and belonging
No full textA period of terrible state repression known as ‘Gukurahundi’ indelibly marked the foundational years of the Zimbabwean nation. The perpetrators of that period still hold power. It has never been subject to an official truth-telling process, nor have the responsible actors been held accountable. Instead, irreconcilable narratives about this past have interacted and, for those subjected to violence, proliferated, producing what I call a ‘noisy silence’ at the edges of the nation. This noise rumbles on because of a perpetual failure of public recognition of the violent past, but it does so in highly varied ways and to distinct purposes. I seek to trace the history of this noisy silence from its start in the irreconcilable narratives of the 1980s, themselves powerfully rooted in earlier liberation struggle ideas and relationships, through subsequent decades. Noisy silence sat in between an official, justificatory account of Gukurahundi on the one hand and the fearful, silenced memories of individuals on the other. It occupied a productive middle ground where collective, creative efforts delineated and demanded new political possibilities and terms of belonging through truth-telling, re-imagined and mourned nations and cross-generational attempts to heal and hold perpetrators to account
From rebel to humanitarian: Military savoire faire and humanitarian practice in eastern DR Congo
No full textThis article explores the experience of ex-rebels who have become humanitarians in the eastern Democratic Republic of the Congo. It describes how rebel-cum-humanitarians navigate a turbulent political environment, integrating the knowledge they acquired through military experience into a career in the humanitarian sector. ‘Distinction’ between combatants and humanitarians remains central to the humanitarian imaginary. However, rebel and humanitarian spheres are interlinked by individuals who do not just broker relationships between the two, but also move between them. They walk a tightrope: their rebel past is seen as a threat to performing a ‘neutral’ humanitarian identity, but at the same time, it constitutes a resource in brokering access with armed groups. Despite a focus on performing principles, humanitarian agencies in practice draw on their employees’ savoir faire which is sometimes gained through rebel experience — the very identity deemed antithetical to a humanitarian status
DatalogMTL with negation under stable models semantics
No full textWe introduce negation under stable models semantics in DatalogMTL—a temporal extension of Datalog with metric operators. As a result, we obtain a rule language which combines the power of answer set programming with the temporal dimension provided by metric operators. We show that, in this setting, reasoning becomes undecidable over the rationals and decidable in EXPSPACE in data complexity over the integers. We also show that, if we restrict our attention to forward-propagating programs (where rules propagate information in a single temporal direction), reasoning over integers becomes PSPACE-complete in data complexity and hence no harder than over positive programs; however, reasoning over the rationals in this fragment remains undecidable
Immunogenicity and safety of a 3-antigen hepatitis B vaccine vs a single-antigen hepatitis B vaccine: A phase 3 randomized clinical trial
No full textImportance There is a need for improved immunogenicity of hepatitis B virus (HBV) vaccines among young adults with risk of infection.
Objectives To demonstrate manufacturing equivalence of a 3-antigen (3A) HBV vaccine, evaluate noninferiority of seroprotection rate (SPR) of 3A-HBV vs single-antigen (1A) HBV after 2 and 3 vaccine doses, and compare safety and reactogenicity between 3A-HBV and 1A-HBV vaccines.
Design, Setting, and Participants This phase 3, double-blinded, randomized clinical trial included healthy adults aged 18 to 45 years randomized to 1 of three 3A-HBV groups or 1 control group receiving 1A-HBV. The trial was conducted at 37 community clinics and academic hospitals in Canada, Europe, the United Kingdom, and the United States between December 2017 and October 2019. Participants were followed up for 48 weeks after the first vaccination.
Interventions Intramuscular administration of 3A-HBV (10 μg) or 1A-HBV (20 μg) on days 0, 28, and 168.
Main Outcomes and Measures Geometric mean concentration (GMC) of serum hepatitis B surface antibodies (anti-HBs) and proportion of participants achieving seroprotection.
Results Of 2838 participants, 1638 (57.8%) were women, 2595 (91.5%) were White, and 161 (5.7%) were Black or African American. A total of 712 participants (25.1%) were randomized to the 1A-HBV group and 2126 (74.9%) to 3A-HBV. The mean (SD) age at informed consent was 33.5 (8.0) years. The study demonstrated 3A-HBV lot-to-lot consistency, as the 2-sided 95% CIs for each pairwise comparison for the anti-HBs GMC ratios were within 0.67 and 1.50 (eg, adjusted GMC ratio, lot A vs lot B: 0.82; 95% CI, 0.67-1.00; lot A vs lot C: 0.95; 95% CI, 0.78-1.15; lot B vs lot C: 1.16; 95% CI, 0.95-1.41). The SPR of the pooled 3A-HBV was noninferior to 1A-HBV and higher than 1A-HBV after 2 vaccinations at day 168 (90.4% [95% CI, 89.0%-91.8%] vs 51.6% [95% CI, 47.5%-55.6%]) and 3 vaccinations at day 196 (99.3% [95% CI, 98.7%-99.6%] vs 94.8% [95% CI, 92.7%-96.4%]). The mean GMC of anti-HBs with 3A-HBV was 7.9 times higher after 2 vaccinations at day 168 and 3.5 times higher after 3 vaccinations at day 196 compared with 1A-HBV (after 2 vaccinations, 3A-HBV: GMC, 118.7 mIU/mL; 95% CI, 108.0-129.0 mIU/mL; SE, 1.0 mIU/mL; 1A-HBV: GMC, 15.0 mIU/mL; 95% CI, 12.9-17.5 mIU/mL; SE, 1.0 mIU/mL; after 3 vaccinations, 3A-HBV: GMC, 5442.4 mIU/mL; 95% CI, 4967.0-5963.0 mIU/mL; SE, 1.0 mIU/mL; 1A-HBV: 1567.2 mIU/mL; 95% CI, 1338.0-1834.0 mIU/mL; SE, 1.0 mIU/mL). Rates of local and systemic reactogenicities were higher with 3A-HBV compared with 1A-HBV (local: 1805 of 2124 [85.0%] vs 469 of 712 [65.9%]; systemic: 1445 [68.0%] vs 428 [60.1%]). Vaccine discontinuation due to adverse events (AE) was uncommon, and serious AEs were infrequent, reported in 42 participants (2.0%) and 3 participants (0.4%) in the 3A-HBV and 1A-HBV groups, respectively.
Conclusions and Relevance In this study, consistently higher antibody concentrations and SPRs were found with 3A-HBV after 2 and 3 doses vs 1A-HBV in adults aged 18 to 45 years old. The safety and efficacy of 3A-HBV shows its usefulness for the prevention of hepatitis B in young healthy adults.
Trial Registration Clinicaltrials.gov Identifier: NCT03408730; EU Clinical Trials Number: 2017-001820-2
Regional variation in inequality of educational opportunity across Europe
No full textA large body of literature documents cross-national variation in the level of inequality of educational opportunity (IEO) among children from different social backgrounds. By contrast, relatively little attention has been given to the extent to which IEO varies within counties and across regions. On the basis of data from the European Social Survey, the authors map variation in IEO across regions in Europe and show that IEO varies substantially within counties. This visualization of the heterogeneity of IEO within European countries highlights the need for researchers and policy makers to extend the current focus on cross-national differences and to investigate and address IEO at the regional level. The visualization raises important questions with respect to the contours, causes, and consequences of cross-regional variation in IEO
Receding-horizon perceptive trajectory optimization for dynamic legged locomotion with learned initialization
No full textTo dynamically traverse challenging terrain, legged robots need to continually perceive and reason about upcoming features, adjust the locations and timings of future footfalls and leverage momentum strategically. We present a pipeline that enables flexibly-parametrized trajectories for perceptive and dynamic quadruped locomotion to be optimized in an online, receding-horizon manner. The initial guess passed to the optimizer affects the computation needed to achieve convergence and the quality of the solution. We consider two methods for generating good guesses. The first is a heuristic initializer which provides a simple guess and requires significant optimization but is nonetheless suitable for adaptation to upcoming terrain. We demonstrate experiments using the ANYmal C quadruped, with fully onboard sensing and computation, to cross obstacles at moderate speeds using this technique. Our second approach uses latent-mode trajectory regression (LMTR) to imitate expert data—while avoiding invalid interpolations between distinct behaviors—such that minimal optimization is needed. This enables high-speed motions that make more expansive use of the robot’s capabilities. We demonstrate it on flat ground with the real robot and provide numerical trials that progress toward deployment on terrain. These results illustrate a paradigm for advancing beyond short-horizon dynamic reactions, toward the type of intuitive and adaptive locomotion planning exhibited by animals and humans