Découverte d’un écrit mathématique du Maghreb médiéval : le commentaire d’al-ˁUqbānī (m. 811/1408

Ibn al-Yāsamīn’s poem in algebra (d. 601/1204) is considered one of the most widely spread mathematical texts in the Maghreb at the end of the Middle Ages. It has been the subject of thirteen comments among which we find that of Abū ˁUṯmān Saˁīd b. Muḥammad al-ˁUqbānī (d. 811/1408). The latter was considered lost by specialists in the history of Arabic mathematics. But after investigations in private libraries, we found a copy of this commentary in a collection of astronomy and mathematics preserved in the Zaouia al-ˁUṯmaniyya of Tolga in Algeria. As it has been written by several scholars, this didactic text testifies to the diffusion of comments and abstracts in the teaching of mathematics in the Muslim West.El poema de Ibn al-Yāsamīn sobre el álgebra (m. 601/1204) se considera como uno de los textos matemáticos más difundidos en el Magreb a finales de la Edad Media. Fue objeto de trece comentarios entre los cuales encontramos el de Abū ˁUṯmān Saˁīd b. Muḥammad al-ˁUqbānī (m. 811/1408). Este último fue considerado perdido por los especialistas en la historia de las matemáticas árabes. Pero después de investigaciones en las bibliotecas privadas, encontramos una copia de este comentario en una colección de astronomía y matemáticas conservada en la zagüía al-ˁUṯmāniyya de Tolga en Argelia. Como ha sido escrito por varios especialistas, este texto didáctico testimonia la difusión de comentarios y resúmenes en la enseñanza de las matemáticas en el Occidente islámico

Découverte d’un écrit mathématique du Maghreb médiéval : le commentaire d’al-ˁUqbānī (m. 811/1408)

El poema de Ibn al-Yāsamīn sobre el álgebra (m. 601/1204) se considera como uno de los textos matemáticos más difundidos en el Magreb a finales de la Edad Media. Fue objeto de trece comentarios entre los cuales encontramos el de Abū ˁUṯmān Saˁīd b. Muḥammad al-ˁUqbānī (m. 811/1408). Este último fue considerado perdido por los especialistas en la historia de las matemáticas árabes. Pero después de investigaciones en las bibliotecas privadas, encontramos una copia de este comentario en una colección de astronomía y matemáticas conservada en la zagüía al-ˁUṯmāniyya de Tolga en Argelia. Como ha sido escrito por varios especialistas, este texto didáctico testimonia la difusión de comentarios y resúmenes en la enseñanza de las matemáticas en el Occidente islámico.Ibn al-Yāsamīn’s poem in algebra (d. 601/1204) is considered one of the most widely spread mathematical texts in the Maghreb at the end of the Middle Ages. It has been the subject of thirteen comments among which we find that of Abū ˁUṯmān Saˁīd b. Muḥammad al-ˁUqbānī (d. 811/1408). The latter was considered lost by specialists in the history of Arabic mathematics. But after investigations in private libraries, we found a copy of this commentary in a collection of astronomy and mathematics preserved in the Zaouia al-ˁUṯmaniyya of Tolga in Algeria. As it has been written by several scholars, this didactic text testifies to the diffusion of comments and abstracts in the teaching of mathematics in the Muslim West

Inter- and intramolecular Diels-Alder/retro-Diels-Alder reactions of 4-silylated oxazoles

4-Silylated oxazoles have been shown to undergo inter- and intramolecular Diels-Alder/retro-Diels-Alder reactions with electron-poor alkynes to generate polysubstituted furans. The ease of synthesis of the requisite oxazoles by the rhodium-catalysed condensation of nitriles with silylated diazoacetate greatly increases the scope of this reaction

AlGaAs inverted strip buried heterostructure lasers

Inverted strip buried heterostructure lasers have been fabricated. These lasers have threshold currents and quantum efficiencies that are comparable to those of conventional buried heterostructure lasers. The optical mode is confined by a weakly guiding strip loaded waveguide which makes possible operation in the fundamental transverse mode for larger stripe widths than is possible for conventional buried heterostructure lasers. Scattering of the laser light by irregularities in the sidewalls of the waveguide, which can be a serious problem in conventional buried heterostructure lasers, is also greatly reduced in these lasers

A versatile standard for bathochromic fluorescence based on intramolecular FRET.

A perylene and a terrylene tetracarboxylic bisimide dyad was prepared in which an efficient energy transfer from the former to the latter is observed. The absorption spectrum of this compound covers a broad range. Bathochromic fluorescence with a high quantum yield was obtained independent of excitation wavelengths (λ < 655 nm). The dyad can be recommended for the use of calibrating fluorescence spectrometers, as well as a fluorescence standard in the bathochromic region

A numerical solution for two-dimensional Fredholm integral equations of the second kind with kernels of the logarithmic potential form

Two dimensional Fredholm integral equations with logarithmic potential kernels are numerically solved. The explicit consequence of these solutions to their true solutions is demonstrated. The results are based on a previous work in which numerical solutions were obtained for Fredholm integral equations of the second kind with continuous kernels

The Phase-Contrast Imaging Instrument at the Matter in Extreme Conditions Endstation at LCLS

We describe the Phase-Contrast Imaging instrument at the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Light Source. The instrument can image phenomena with a spatial resolution of a few hundreds of nanometers and at the same time reveal the atomic structure through X-ray diffraction, with a temporal resolution better than 100 femtosecond. It was specifically designed for studies relevant to High-Energy-Density Science and can monitor, e.g., shock fronts, phase transitions, or void collapses. This versatile instrument was commissioned last year and is now available to the MEC user community

Trophic status and phytoplankton in Lake Bidighinzu

From March 1988 to April 1989 a survey was carried out on the phytoplankton of Lake Bidighinzu, a hypertrophic reservoir in Northern Sardinia. The purpose of this work was to assess the general limnological conditions of the reservoir after a diversion of the urban and industrial wastes. The dynamics of chlorophyll a, and the structure and composition of the phytoplankton density and of its biomass in the study period were determined. Moreover the found trends for trasparency, temperature, conductivity, alkalinity, pH, dissolved oxygen, reactive and total phosphorus, nitrate, nitrite, ammonium nitrogen, and reactive silica are reported. The effect of water aeration on the dynamics of the other parameters is discussed