12,472 research outputs found

    Primitive abundant and weird numbers with many prime factors

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    We give an algorithm to enumerate all primitive abundant numbers (briefly, PANs) with a fixed Ω\Omega (the number of prime factors counted with their multiplicity), and explicitly find all PANs up to Ω=6\Omega=6, count all PANs and square-free PANs up to Ω=7\Omega=7 and count all odd PANs and odd square-free PANs up to Ω=8\Omega=8. We find primitive weird numbers (briefly, PWNs) with up to 16 prime factors, improving the previous results of [Amato-Hasler-Melfi-Parton] where PWNs with up to 6 prime factors have been given. The largest PWN we find has 14712 digits: as far as we know, this is the largest example existing, the previous one being 5328 digits long [Melfi]. We find hundreds of PWNs with exactly one square odd prime factor: as far as we know, only five were known before. We find all PWNs with at least one odd prime factor with multiplicity greater than one and Ω=7\Omega = 7 and prove that there are none with Ω<7\Omega < 7. Regarding PWNs with a cubic (or higher) odd prime factor, we prove that there are none with Ω≤7\Omega\le 7, and we did not find any with larger Ω\Omega. Finally, we find several PWNs with 2 square odd prime factors, and one with 3 square odd prime factors. These are the first such examples.Comment: New section on open problems. A mistake in table 2 corrected (# odd PAN with Omega=8). New PWN in table 5, last line, 2 squared prime factors, Omega=15. Updated bibliograph

    Methodological and terminological issues in animal-assisted interventions: An umbrella review of systematic reviews

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    Recently, animal-assisted interventions (AAIs), which are defined as psychological, educational, and rehabilitation support activities, have become widespread in different contexts. For many years, they have been a subject of interest in the international scientific community and are at the center of an important discussion regarding their effectiveness and the most appropriate practices for their realization. We carried out an umbrella review (UR) of systematic reviews (SRs), created for the purpose of exploring the literature and aimed at deepening the terminological and methodological aspects of AAIs. It is created by exploring the online databases PubMed, Google Scholar, and Cochrane Library. The SRs present in the high-impact indexed search engines Web of Sciences and Scopus are selected. After screening, we selected 15 SRs that met the inclusion criteria. All papers complained of the poor quality of AAIs; some considered articles containing interventions that did not always correspond to the terminology they have explored and whose operating practices were not always comparable. This stresses the need for the development and consequent diffusion of not only operational protocols, but also research protocols which provide for the homogeneous use of universally recognized terminologies, thus facilitating the study, deepening, and comparison between the numerous experiences described

    Teaching Preeminence in Renaissance Florence: Leonardo Bruni’s Translation and Dedication of Pseudo-Aristotle’s Economics

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    Renaissance scholars consider Leonardo Bruni’s translation of the Pseudo-Aristotelian Economics, a work dedicated to Cosimo de’ Medici in 1420, the beginning of the Italian humanists’ interaction with newly readable Greek sources. The text was among the first Greek documents Westerners embraced and translated into Latin or the vernacular of the Quattrocento. Thus, it played a significant role in the revival of the ancient Greek language amongst humanists, which was largely lost since the fall of the Roman Empire. However, this paper argues that Bruni’s translation of the Pseudo-Aristotelian Economics also represents the utilization of an important Roman source: Seneca the Younger. Seneca was among the most well known Roman authors in the Renaissance. Nevertheless, his usage and influence in Florence, especially in Leonardo Bruni’s vast repertoire, has gone unnoticed. Historians have overlooked this because of a tendency to emphasize the significance of his study of the novel Greek documents. Still, when translating the Economics, this humanist appears to have taken the opportunity to disseminate Senecan ideals, particularly the correlations between wealth, magnanimity, and societal and gubernatorial preeminence. This paper also argues that the presence of Senecan rhetoric in the translation, coupled with its dedication to Cosimo de’ Medici, represents Leonardo Bruni’s political posturing. Seneca first used these philosophies now present in Bruni’s translation to promote the preeminence of the Roman princeps, a term that Romans used to identify the Emperor, or first citizen, and to justify the his position in the Roman republic. This rhetoric seems to have served a similar purpose in Renaissance Florence. It served to teach Florentine citizens and politicians how the possession of wealth could bring about and enhance ancient ideals of leadership. It simultaneously advertised its dedicatee’s ability to embody these ideals, and thus, promoted the fruition of a Medici regime

    Global and regional importance of the direct dust-climate feedback.

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    Feedbacks between the global dust cycle and the climate system might have amplified past climate changes. Yet, it remains unclear what role the dust-climate feedback will play in future anthropogenic climate change. Here, we estimate the direct dust-climate feedback, arising from changes in the dust direct radiative effect (DRE), using a simple theoretical framework that combines constraints on the dust DRE with a series of climate model results. We find that the direct dust-climate feedback is likely in the range of -0.04 to +0.02 Wm -2 K-1, such that it could account for a substantial fraction of the total aerosol feedbacks in the climate system. On a regional scale, the direct dust-climate feedback is enhanced by approximately an order of magnitude close to major source regions. This suggests that it could play an important role in shaping the future climates of Northern Africa, the Sahel, the Mediterranean region, the Middle East, and Central Asia

    The epidermal ‘excretory’ syncytial plates in species of Temnocephala (Platyhelminthes, Temnocephalida): Proposal of a new methodology

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    The epidermis of temnocephalids is formed by a mosaic of syncytial plates as revealed by electron microscopy and/or 5% silver nitrate impregnation. The variable form and size have been observed but the value of the epidermal ‘excretory’ syncytial plates (EPs) in the identification of Temnocephala species never were proper discuss. Ten species of Temnocephala were studied using images taken with a scanning electron microscope (SEM), describing a morphometry method to allow the comparison, thus, evaluating the EPs as a specific character in the identification of species of Temnocephala. The measurements (length of the anterior and posterior portions of the plate relative to the excretory pore, width of the internal and external limits, length of the portion exceeding the tentacles, total width, and total length) were obtained using AxioVision® Zeiss LWE 4.7.2 (AVZ) software. The EPs of the species tested were different revealing unique characteristics thus allowing their use as specific characters within Temnocephala. There was a pattern for each host group (Mollusca, Crustacea, Insecta, and Chelonia); the exceptions were the crustacean species and one insect species. The intra-specific variation study in Temnocephala trapeziformis demonstrated that this character varied minimally within the species. The SEM images and the AVZ software measurements were positive for the characterization of species of Temnocephala. The cirrus remained the most important specific character within Temnocephala. The traditional morphometric method was sufficient to demonstrate several specific EP characteristics, but new EPs should always be clearly described and illustrated following the now proposed methodology for Temnocephala species identification.(As placas epidérmicas sinciciais ‘excretoras’ em espécies de Temnocephala (Platyhelminthes, Temnocephalida): Proposta de uma nova metodologia.) A epiderme dos representantes da ordem Temnocephalida é formada por um mosaico de placas epidérmicas sinciciais evidenciado através da microscopia eletrônica e da impregnação com nitrato de prata 5%. A variação de forma e tamanho do par de sincícios pós-tentaculares, ou ‘placas excretoras’ (PEs), entre as espécies já foram observados, mas o valor das PEs na identificação de espécies de Temnocephala nunca foi adequadamente discutido. Dez espécies de Temnocephala foram analisadas através de imagens obtidas em microscopia eletrônica de varredura (MEV), descrevendo um método morfométrico que permite a comparação, e avaliação, das PEs como carácter específico. As medidas (comprimento da porção anterior e posterior, largura do limite interno e externo, comprimento da porção da placa acima do limite dos tentáculos, comprimento e largura totais) foram obtidas no programa AxioVision Zeiss LE 4.7.2 (AVZ). As PEs das espécies estudadas diferiram entre si e possuem características únicas que fazem delas bons caracteres diagnósticos específicos. Possuem um padrão por grupo hospedeiro; as exceções são as espécies epibiontes em crustáceos e uma espécie epibionte em insetos. O estudo da variação intraespecífica de Temnocephala trapeziformis mostrou que este caráter tem pouca variação dentro de uma mesma espécie. A visualização das PEs em MEV e as medidas obtidas através do programa AVZ produziram bons resultados na caracterização das espécies. O estudo morfométrico tradicional foi suficiente para evidenciar as características específicas das PEs. Estas devem ser claramente descritas e ilustradas, seguindo a metodologia agora proposta, para permitir a utilização deste caráter diagnóstico na identificação das espécies de Temnocephala

    Facilitating the exploitation of ERTS-1 imagery using snow enhancement techniques

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    The author has identified the following significant results. The applications of ERTS-1 imagery for geological fracture mapping regardless of season has been repeatedly confirmed. The enhancement provided by a differential cover of snow increases the number and length of fracture-lineaments which can be detected with ERTS-1 data and accelerates the fracture mapping process for a variety of practical applications. The geological mapping benefits of the program will be realized in geographic areas where data are most needed - complex glaciated terrain and areas of deep residual soils. ERTS-1 derived fracture-lineament maps which provide detail well in excess of existing geological maps are not available in the Massachusetts-Connecticut area. The large quantity of new data provided by ERTS-1 may accelerate and improve field mapping now in progress in the area. Numerous other user groups have requested data on the techniques. This represents a major change in operating philosophy for groups who to data judged that snow obscured geological detail

    Edible insects and global food security

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    Starting in 2008 and lasting up until 2011, the crisis in agricultural and, in particular, cereal prices triggered a period of riots that spread from the Mediterranean basin to the rest of the world, reaching from Asia to Central America and the African continent. [...]

    Application of EREP imagery to fracture-related mine safety hazards and environmental problems in mining

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    The author has identified the following significant results. All Skylab 2 imagery received to date has been analyzed manually and data related to fracture analysis and mined land inventories has been summarized on map-overlays. A comparison of the relative utility of the Skylab image products for fracture detection, soil tone/vegetation contrast mapping, and mined land mapping has been completed. Numerous fracture traces were detected on both color and black and white transparencies. Unique fracture trace data which will contribute to the investigator's mining hazards analysis were noted on the EREP imagery; these data could not be detected on ERTS-1 imagery or high altitude aircraft color infrared photography. Stream segments controlled by fractures or joint systems could be identified in more detail than with ERTS-1 imagery of comparable scale. ERTS-1 mine hazards products will be modified to demonstrate the value of this additional data. Skylab images were used successfully to update a mined land map of Indiana made in 1972. Changes in mined area as small as two acres can be identified. As the Energy Crisis increases the demand for coal, such demonstrations of the application of Skylab data to coal resources will take on new importance

    Fracture mapping and strip mine inventory in the Midwest by using ERTS-1 imagery

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    Analysis of the ERTS-1 imagery and high-altitude infrared photography indicates that useful fracture data can be obtained in Indiana and Illinois despite a glacial till cover. ERTS MSS bands 5 and 7 have proven most useful for fracture mapping in coal-bearing rocks in this region. Preliminary results suggest a reasonable correlation between image-detected fractures and mine roof-fall accidents. Information related to surface mined land, such as disturbed area, water bodies, and kind of reclamation, has been derived from the analysis of ERTS imagery
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