82 research outputs found

    Speciation, Luminescence, and Alkaline Fluorescence Quenching of 4-(2-methylbutyl)aminodipicolinic acid (H2MEBADPA)

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    4-(2-Methylbutyl)aminodipicolinic acid (H2MEBADPA) has been synthesized and fully characterized in terms of aqueous phase protonation constants (pKa\u27s) and photophysical measurements. The pKa\u27s were determined by spectrophotometric titrations, utilizing a fully sealed titration system. Photophysical measurements consisted of room temperature fluorescence and frozen solution phosphorescence as well as quantum yield determinations at various pH, which showed that only fully deprotonated MEBADPA2– is appreciably emissive. The fluorescence of MEBADPA2– has been determined to be quenched by hydroxide and methoxide anions, most likely through base-catalyzed excited-state tautomerism or proton transfer. This quenching phenomenon has been quantitatively explored through steady-state and time-resolved fluorescence measurements. Utilizing the determined pKas and quenching constants, the fluorescent intensity of MEBADPA2– has been successfully modeled as a function of pH

    Scaling the state: Egypt in the third millennium BC

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    Discussions of the early Egyptian state suffer from a weak consideration of scale. Egyptian archaeologists derive their arguments primarily from evidence of court cemeteries, elite tombs, and monuments of royal display. The material informs the analysis of kingship, early writing, and administration but it remains obscure how the core of the early Pharaonic state was embedded in the territory it claimed to administer. This paper suggests that the relationship between centre and hinterland is key for scaling the Egyptian state of the Old Kingdom (ca. 2,700-2,200 BC). Initially, central administration imagines Egypt using models at variance with provincial practice. The end of the Old Kingdom demarcates not the collapse, but the beginning of a large-scale state characterized by the coalescence of central and local models

    Geophysical methods in the archaeological study of ancient Egyptian cities

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    Podczas ostatnich dwóch dekad nastąpił gwałtowny postęp w poznawaniu zespołów miejskich starożytnego Egiptu. Stało się to możliwe dzięki zastosowaniu metody magnetycznej, pozwalającej rekonstruować plany miast na obszarach o powierzchni dziesiątek hektarów – niemożliwych do przebadania przy użyciu konwencjonalnych metod wykopaliskowych. Metoda jest szczególnie efektywna w przypadku badań zabudowy w delcie Nilu, a także w dolinie Nilu i na jej na obrzeżach, czyli tam, gdzie podstawowym materiałem budowlanym była suszona w słońcu cegła, wytwarzana z mułu nilowego – surowca o dużej zawartości tlenków żelaza, a zatem łatwego do rejestracji przy użyciu metody magnetycznej. W korzystnych warunkach prospekcja magnetyczna daje na tyle dokładny obraz niewidocznej na powierzchni zabudowy, iż na podstawie cech typowych dla danych okresów rozwoju architektury egipskiej można wstępnie określać datę powstania budynków. Pomiary pozwalają także na rejestrowanie miejsc pochówków, struktur o charakterze produkcyjnym (np. piece do produkcji ceramiki). Obszary prowadzone na dużych przestrzeniach pozwalają na rekonstrukcję zmian w krajobrazie (np. poprzez odtworzenie sieci nieistniejących kanałów czy odnóg rzecznych). W pomiarach używane są dwa typy magnetometrów: gradientometry turboptrzepływowe mierzące wektor pionowy natężenia pola magnetycznego oraz magnetometry pompowane optycznie, mierzące całkowite natężenia pola. Gęstość próbkowania wynosi zwykle od 8 do 20 pomiarów na metr kwadratowy. Poza metodą magnetyczną, w badaniach znajduje także zastosowanie metoda elektrooporowa, głównie w wersji profilowań. Jest ona przydatna w badaniach zabudowy z epoki rzymskiej, gdy podstawowym materiałem budowlanym była cegła palona. Gęstość próbkowania wynosi 1 lub 2 pomiary na metr kwadratowy. W artykule przedstawione są wyniki badań autora na stanowiskach z epok począwszy od Średniego Państwa (1 poł. II tysiąclecia przed Chr.) do schyłku pierwszego tysiąclecia po Chr.Huge progress has been made over the last two decades in research on ancient Egyptian cities, mainly by means of the magnetic method, which has enabled city plans to be reconstructed over dozens of hectares – something conventional excavation methods do not allow. The method is particularly effective in the case of research in the valley and delta of the Nile, where the basic building material was sun-dried brick made of Nile mud, a material rich in iron oxides, easily registered using the magnetic method. Under the right circumstances, magnetic surveying provides an image of subterranean structures, sufficiently precise to date structures on the grounds of characteristics typical for Egyptian architecture of different periods. The readings can also register burials and industrial features (e.g. pottery-production furnaces). Surveys of larger areas support reconstructions of the paleo-landscape (e.g. by recreating canal networks and Nile branches). Measurements are taken using two kinds of instruments: fluxgate gradiometers (measuring the vertical component of the magnetic field) and optically pumped (measuring the total value of the magnetic field). The sampling grid is between 8 and 20 measurements per square meter. Surveying with the resistivity method (mainly profiling) has proved useful for examining sites from the Roman period, when fired brick was the basic material in use for building purposes. The sampling grid in this case is 1 or 2 measurements per square meter. The article presents the author’s research on sites from the Middle Kingdom (the first half of the 2nd millennium BC) to the end of the 1st millennium AD

    Kernel Topic Models

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    {Latent Dirichlet Allocation models discrete data as a mixture of discrete distributions, using Dirichlet beliefs over the mixture weights. We study a variation of this concept, in which the documents' mixture weight beliefs are replaced with squashed Gaussian distributions. This allows documents to be associated with elements of a Hilbert space, admitting kernel topic models (KTM), modelling temporal, spatial, hierarchical, social and other structure between documents. The main challenge is efficient approximate inference on the latent Gaussian. We present an approximate algorithm cast around a Laplace approximation in a transformed basis. The KTM can also be interpreted as a type of Gaussian process latent variable model, or as a topic model conditional on document features, uncovering links between earlier work in these areas.

    Magnetic Gradient and Electrical Resistivity Tomography Surveys in Meroe, the Capital City of the Kush Kingdom, Sudan

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    One of the most important archaeological sites in Sudan is Meroe, capital city of the kingdom of Kush (800 bc to ad 400). The site is located in the Nile valley, about 200 km northeast of Khartoum. The most prominent feature among the ruins of Meroe is the Royal City: a stone-walled enclosure containing remains of palaces, governmental buildings and temples. The current study presents the results of integrated magnetic gradient and electrical resistivity tomography surveys in unexplored and partly explored areas in the central part of the site and in the southern part of the Royal City. The main enclosure wall, remains of sandstone and red-brick buildings, and a number of small archaeological structures have been traced on magnetic maps. The extent of buildings, identified by magnetic survey, has been complemented by information on the depth of structures provided by electrical resistivity tomography. The geophysical results have been partly verified through excavation
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