The introduction of Grationality at a 2025 sectional meeting of the Mathematical Association of America installed a handle on a concept akin to rationality of numbers, but in a geometric context. A nice $n$-gon was defined to be a regular $n$-gon with side lengths that are natural numbers, and a number $n$ was defined to be grational if and only if there exists a nice $n$-gon such that its area equals the sum of areas of $n$ congruent nice $n$-gons. This paper shows several examples of grational and non-grational numbers, followed by theorems about how the grationality of a number relates to its divisibility. Proofs of these theorems do not use high-powered tools, but rely on geometric constructions, proportional reasoning, tiling, dissection, the Carpets Theorem, and proof by descent. In keeping with this simplicity, a.k.a. "doing math with a spoon," images are heavily leveraged. The benefits of choosing simplistic tools are discussed.
IntroductionStanding milkvetch (Astragalus adsurgens) is widely distributed in the wild in Eurasia and North America and has been bred for cultivated forage in China. Yellow stunt and root rot disease caused by Alternaria gansuense is the primary disease of standing milkvetch. A. gansuense promotes the production of swainsonine in the plant. This study aimed to determine the safety of standing milkvetch that is infected with A. gansuense as forage for animals.MethodsTwo-week-old specific pathogen-free (SPF) male white mice were fed a commercial mouse feed (CMF), healthy plant feed (HPF) and diseased plant feed (DPF) for 3 or 6 weeks. We observed histological changes in the liver and kidney tissues of the mice and measured their daily feed intake, daily water intake, body weight, feed utilization, organ coefficients, and activities of serum enzymes.ResultsThe results showed that the daily feed intake of the mice that were fed DPF and HPF was significantly higher (p < 0.05) than those fed CMF at 3 and 6 weeks. The highest increase was observed in the daily water intake of the mice fed HPF (p < 0.05) followed by DPF and CMF. However, the mice fed DPF gained the least weight (p < 0.05). There was a significantly higher percentage of liver weight to body weight of the mice fed DPF (p < 0.05) than those fed HPF for 3 weeks and those fed CMF for 3 and 6 weeks. There were significantly higher levels of concentrations of alanine aminotransferase in the mice fed DPF and HPF than those fed CMF for 3 weeks (p < 0.05) and 6 weeks (p < 0.01). However, there was no significant difference in the mice fed HPF than those fed DPF. There were significantly higher of lactate dehydrogenase concentration (p < 0.001), while the blood urea nitrogen was lower in the mice fed DPF than those fed HPF and CMF at 3 weeks. There was a significantly higher percentage of numbers of lymphocytes in the blood of the mice fed DPF (p < 0.05) than those fed HPF, but the percentages of monocytes and eosinophils were significantly lower. Comparatively, there were more apparent pathological changes in the liver and kidney tissues of the mice fed with DPF than in those fed with HPF.DiscussionThese findings indicate that standing milkvetch was toxic to white mice, and infection with A. gansuense increased its toxicity. Therefore, we conclude that standing milkvetch plants infected by A. gansuense must never be used as animal feed under any circumstances. Additionally, the amount of healthy standing milkvetch fed to animals should be appropriate, avoiding long-term or excessive feeding.
It has long been established that, if a panel dataset suffers from attrition, auxiliary (refreshment) sampling restores full identification under additional assumptions that still allow for nontrivial attrition mechanisms. Such identification results rely on implausible assumptions about the attrition process or lead to theoretically and computationally challenging estimation procedures. We propose an alternative identifying assumption that, despite its nonparametric nature, suggests a simple estimation algorithm based on a transformation of the empirical cumulative distribution function of the data. This estimation procedure requires neither tuning parameters nor optimization in the first step, i.e., it has a closed form. We prove that our estimator is consistent and asymptotically normal and demonstrate its good performance in simulations. We provide an empirical illustration with income data from the Understanding America Study.
Nana Mgbechikwere Nwachukwu, Jennafer Shae Roberts, Laura N Montoya
To harness the true potential of Artificial Intelligence (AI) for societal betterment, we need to move away from prioritising corporate interests which exploit Global South workers in the digital age. The unpaid labour and societal harms which are generated by Digital Value Networks (DVNs) disproportionately affect workers in Africa, Latin America, and India and need to be regulated. In this research, we discuss unethical practices to automate Human Intelligence Tasks (HITs) through gig work platforms and the capitalisation of data collection utilising influencers in social media. These are important areas of study in worker and user data practices, where ethical AI could be impactful. We provide suggestions for a path forward focused on responsible AI development.
The output of solar power generation is significantly dependent on the available solar radiation. Thus, with the proliferation of PV generation in the modern power grid, forecasting of solar irradiance is vital for proper operation of the grid. To achieve an improved accuracy in prediction performance, this paper discusses a Bayesian treatment of probabilistic forecasting. The approach is demonstrated using publicly available data obtained from the Florida Automated Weather Network (FAWN). The algorithm is developed in Python and the results are compared with point forecasts, other probabilistic methods and actual field results obtained for the period.
In 21st century America, to many observers, the idea that 10's of millions of Americans could lose power and heat for multiple days in the middle of a record cold snap, was unthinkable. It came as an even greater surprise that it would be Texas - arguably one of the world's energy capitals - that failed to provide sufficient power to its residents. This paper explores the events that led to the outage, the experiences of those who lived through it, and the situation in Texas one to two months after the event. We have taken an ethnographic approach to capture both the empirical aspects of the situation, and the more interpretive descriptions of the accounts and thoughts of the participants. We believe this ethnography of events in Texas can serve as foundational evidence and therefore can be generalized to a wide variety of situations and methodologies.
Magnus Danel Hammer, Christopher C. Finlay, Nils Olsen
We use 20 years of magnetic field measurements from the Oersted, CHAMP and Swarm satellite missions, supplemented by calibrated platform magnetometer data from the CryoSat2 satellite, to study time variations of the Earth's core field at satellite altitude and at the core-mantle boundary (CMB). From the satellite data we derive composite time series of the core field secular variation (SV) with 4month cadence, at 300 globally distributed Geomagnetic Virtual Observatories (GVO). GVO radial SV series display regional fluctuations with 5-10 years duration and amplitudes reaching 20 nT/yr, most notably at low latitudes over Indonesia (2014), over South America and the South Atlantic (2007, 2011 and 2014), and over the central Pacific (2017). Applying the Subtractive Optimally Localized Averages (SOLA) method, we map the SV at the CMB as a collection of locally averaged SV estimates. We demonstrate that using 2-year windows of CryoSat2 data, it is possible to reliably estimate the SV and its time derivative, the secular acceleration (SA), at the CMB, with a spatial resolution, corresponding to spherical harmonic degree 10. Along the CMB geographic equator, we find strong SA features under Indonesia from 2011-2014, under central America from 2015 to 2019, and sequences of SA with alternating sign under the Atlantic during 2004-2019. We find that data from CryoSat2 make a valuable contribution to the emerging picture of sub-decadal core field variations. Using 1 year windows of data from the Swarm satellites, it is possible to study SA changes at low latitudes on timescales down to 1 year, with spatial resolution corresponding to spherical harmonic degree 10. We find strong positive and negative SA features appearing side-by-side in the Pacific in 2017, and thereafter drift westward.
Sara Zahedian, Kaveh Farokhi Sadabadi, Amir Nohekhan
This paper introduces a visual-based localization method for autonomous vehicles (AVs) that operate in the absence of any complicated hardware system but a single camera. Visual localization refers to techniques that aim to find the location of an object based on visual information of its surrounding area. The problem of localization has been of interest for many years. However, visual localization is a relatively new subject in the literature of transportation. Moreover, the inevitable application of this type of localization in the context of autonomous vehicles demands special attention from the transportation community to this problem. This study proposes a two-step localization method that requires a database of geotagged images and a camera mounted on a vehicle that can take pictures while the car is moving. The first step which is image retrieval uses SIFT local feature descriptor to find an initial location for the vehicle using image matching. The next step is to utilize the Kalman filter to estimate a more accurate location for the vehicle as it is moving. All stages of the introduced method are implemented as a complete system using different Python libraries. The proposed system is tested on the KITTI dataset and has shown an average accuracy of 2 meters in finding the final location of the vehicle.
In this study, we propose a time-dependent Susceptible-Exposed-Infected-Recovered (SEIR) model for the analysis of the SARS-CoV-2 epidemic outbreak in three different countries, the United States of America, Italy and Iceland using public data inherent the numbers of the epidemic wave. Since several types and grades of actions were adopted by the governments, including travel restrictions, social distancing, or limitation of movement, we want to investigate how these measures can affect the epidemic curve of the infectious population. The parameters of interest for the SEIR model were estimated employing a composite likelihood approach. Moreover, standard errors have been corrected for temporal dependence. The adoption of restrictive measures results in flatten epidemic curves, and the future evolution indicated a decrease in the number of cases.
Ana Maria Marques, Ana Carolina do Nascimento Albuquerque
Este artigo parte do diagnóstico de invisibilidade das mulheres nos livros didáticos de História e aborda a importância de considerar a interseccionalidade de raça e classe nas análises de gênero. Analisa a trajetória de pesquisas sobre livros didáticos, os avanços identificados por meio do PNLD 2018, as indicações do Guia dos Livros Didáticos e duas coleções didáticas: História, Sociedade & Cidadania e História das cavernas ao terceiro milênio. Apesar do crescimento dos estudos de gênero, a pesquisa aponta para uma ausência de mulheres e ainda mais do protagonismo delas.
Latin America. Spanish America, Social sciences (General)
Memory making in schools evidences complex elaborations produced by their agents, as well as an equally heavy link with the contexts in which it is developed. Grasping this complexity is a challenge for those who study this subject. Through the analysis ofcompositionswritten by two groups of students in a public and a private high school from the city center of La Plata, I propose a survey on the mediations between youth people and recent past, and on their social representations. The definition of categories and the qualitative as well as quantitative study of their links in the interpretative and justifying dimensions show us,on the one hand, the persistence of school culture and a nationalistic and formally liberal frame of reference. On the other hand, identifications, appropriations, certain political attitudes and inventiveties with social memories are witnessed. Finally, a contrast between public and private schools is also attested.Thus, I explore memory making on the grounds in which it is elaborated and not only in relation to the values researchers have for the sake of democratization, which in turn constitute a necessary but not a sufficient condition.
Theory and practice of education, History (General)