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  • 1
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    Institut de recherches et d’études sur les mondes arabes et musulmans
    Publication Date: 2022-01-31
    Description: Cet ouvrage regroupe les communications au séminaire ""Villes et Migrations"" qui s'est tenu à l'I.R.Ε.M.A.M. en janvier 1988, dans le cadre de son programme de recherches sur les Migrations Internationales. L'opportunité de pouvoir proposer des interventions homogènes quant à l'espace étudié ainsi que le souci de mieux appréhender une certaine actualité régionale nous a conduit à centrer ce séminaire sur Marseille et sa région mais en enrichissant les analyses proposées de quelques exemples pr...
    Keywords: Tunis ; immigration ; mobilité ; Algérie ; Marseille ; villes ; migration
    Language: French
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  • 2
    Publication Date: 2024-04-01
    Description: Depuis quelques décennies, les pays du Sud assistent à la fuite de leurs « cerveaux » vers les pays du Nord, un phénomène préjudiciable à la formation de leurs cadres et de leurs élites scientifiques nationales, inquiétant pour leur développement. Cependant, on observe depuis quelques années un processus qui pourrait compenser pour partie cette fuite de matière grise. En effet, par des apports informels, les communautés expatriées aident, conseillent et informent les institutions et les chercheurs de leurs pays d'origine. Quelle est l'ampleur du phénomène ? Quelles formes principales revêt-il ? Quelle est son efficacité ? Les responsables des pays d'origine et des pays d'accueil doivent-ils soutenir ce type d'initiatives informelles ? Si oui, par quels moyens et que peut-on en attendre ?
    Keywords: H1-99 ; innovation ; Inde ; politique de la recherche ; coopération technique ; étudiant ; États-Unis ; Afrique du Sud ; migration internationale ; enseignement supérieur ; niveau d’instruction ; diaspora scientifique ; coopération scientifique ; monde ; Chine ; France ; Afrique ; tiers monde ; thema EDItEUR::N History and Archaeology::NH History
    Language: French
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  • 3
    Publication Date: 2024-04-01
    Description: Energieszenarien sind ein wesentliches Mittel zur Entscheidungsunterstützung in Politik und Wirtschaft. Für Infrastrukturentscheidungen im Energiebereich sind lange Zeiträume geltend. Daher ist eine sorgfältige Analyse möglicher ""Energiezukünfte"" von hoher Bedeutung. In diesem Band finden sich sowohl Beiträge von Wissenschaftlern als auch von Akteuren aus der Praxis, die sich mit Methodologie, Konstruktion und Bewertung von Energieszenarien in Gesellschaft, Politik und Wirtschaft beschäftigen.
    Keywords: H1-99 ; Zukunft ; Szenarien ; Energie ; Szenarienmethodik ; Energiemodelle ; thema EDItEUR::N History and Archaeology::NH History
    Language: German
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  • 4
    Publication Date: 2024-04-01
    Description: The book compiles a portion of the contributions presented during the symposium “Urbanisation, commerce, subsistence and production during the third millennium BC on the Iranian Plateau”, which took place at the Maison de l’Orient et de la Méditerranée in Lyon, the 29-30 of April, 2014. The twenty papers assembled provide an overview of the recent archaeological research on this region of the Middle East during the Bronze Age. The socio-economic transformation from rural villages to towns and nations has prompted many questions into this evolution of urbanisation. What was the impact of interactions between cultures in the Iranian Plateau and the surrounding regions (Mesopotamia, the South Caucasus, Central Asia, Indus Valley)? What was the overall context during the Bronze Age on the Iranian Plateau? What was the extent and means of the expansion of the Kuro-Araxe culture? How did the Elamite Kingdom become established? What new knowledge has been contributed by the recent excavations and studies undertaken in the east of Iran? What was the influence of the Indus Valley culture, known as an epicentre of urbanisation in South Asia? What are the unique characteristics of the ancient cultures in Iran? While the urbanisation of early Mesopotamia has been the subject of much debate for several decades, this topic has only recently been raised in respect to the Iranian Plateau. This volume is the product of an international community from Iranian, European, and American institutions, consisting of recognised specialists in the archaeology of the Iranian Bronze Age. It provides an overview of the latest research, including abundant results from current on-going excavations. The current state of archaeological research in Iran, comprising many dynamic questions and perspectives, is presented here in the form of original contributions on the first emergence of towns in the Near and Middle East.
    Keywords: H1-99 ; Iron Age ; Near East ; Central Asia ; iconography ; Middle East ; Mesopotamia ; Elam ; archaeology ; Kura-Araxes ; Bronze Age ; geoarchaeology ; bioarchaeology ; thema EDItEUR::N History and Archaeology::NH History
    Language: English
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 513-516 
    ISSN: 0044-2313
    Keywords: Synthesis ; Crystal Structure ; Lanthanides ; Ternary Lithium Nitrates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structure of the First Anhydrous Ternary Lithium Nitrates of the Lanthanides, Li2[M(NO3)5] (M = La, Pr—Eu).Single crystals of the ternary lithium nitrates of the lanthanides, Li2[M(NO3)5] (M = La, Pr—Eu), are obtained by dissolving the respective anhydrous nitrate, previously obtained by dehydration of M(NO3)3 · 6 H2O at 180°C under vacuum, in a melt of LiNO3. In the crystal structure of Li2[Pr(NO3)5] (orthorhombic, Pnnm, Z = 4, a = 899.6(2), b = 1 052.7(2), c = 1 178.6(2)pm; R = 0.072, Rw = 0.034) there are two crystallographically different Pr3+ ions, each surrounded by six bidentate nitrate ligands. One nitrate group is bridging between Pr1 and Pr2 resulting in a winded chain, ∞1[(O2/2NO2/1)Pr1(NO3)4(O2/2NO2/1)Pr2(O2/2NO2/1)(NO3)4]5-, running along [010]. The chains are packed hexagonally and held together by lithium ions. The coordination polyhydron of Li+ may be described as a bicapped trigonal prism.
    Notes: Einkristalle der ternären Nitrate der Lanthanide vom Typ Li2[M(NO3)5] (M = La, Pr—Eu) erhält man durch Auflösen der zuvor bei 180°C unter Vakuum entwässerten Hydrate M(NO3)3 · 6 H2O in einer Lithiumnitrat-Schmelze. Die Röntgenstrukturanalyse am Beispiel von Li2[Pr(NO3)5] (orthorhombisch, Pnnm, Z = 4; a = 899,6(2); b = 1 052,7(2); c = 1 178,6(2)pm; R = 0,072; Rw = 0,034) zeigt, daß zwei kristallographisch verschiedene Pr3+ vorliegen, die von jeweils sechs zweizähnigen Nitratliganden umgeben sind. Eine Nitratgruppe verbrückt zwischen Pr1 und Pr2, so daß sich eine gewundene Kette gemäß ∞1[(O2/2NO2/1)Pr1(NO3)4(O2/2NO2/1)Pr2(O2/2NO2/1)(NO3)4]5- ergibt, die längs [010] verläuft. Die Kettenstränge sind gemäß einer hexagonalen Stabpackung angeordnet und werden durch Li+-Ionen zusammengehalten. Die Koordination um Li+ kann als zweifach bekapptes trigonales Prisma beschrieben werden.
    Additional Material: 4 Ill.
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  • 6
    ISSN: 0044-2313
    Keywords: Rare Earth Elements ; Halides ; Clusters ; Cesium Scandium Chloride Carbide ; Cesium Praseodymium Iodide Dicarbide ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cs4[Sc6C]Cl13 and Cs4[Pr6(C2)]I13  -  Two Examples for the Missing Link in the Connectivity of [M6Z]X12iX6a Building UnitsCs4[Sc6C]Cl13 (tetragonal, I41/amd, a = 1 540.5(4), c = 1 017.9(7) pm, c/a = 0.661, Z = 4, R = 0.038, Rw = 0.026) and Cs4[Pr6(C2)]I13 (a = 1 804.9(3), c = 1 259.5(3) pm, c/a = 0.698, R = 0.106, Rw = 0.068) are obtained as green-black and blue-black single crystals with brass-like metallic lustre through metallothermic reduction of ScCl3 and PrI3, respectively, with cesium in the presence of carbon in sealed tantalum containers. The, overall, isotypic compounds contain isolated [Sc6C] and [Pr6(C2)] clusters, respectively, that are surrounded by 18 halide (X) ligands (12 Xi and 6 Xa; X = Cl or I). The connection is carried out via the motif [M6Z]X8iX4/21-aX4/2a-1X2/2a-a (M = Sc and Pr; Z = C and C2, respectively) and is thereby the missing link of the motifs of connection for the composition Ax[M6Z]X13. Analogous interconnection of [TiO6] octahedra is found in the anatase-type of structure of TiO2.
    Notes: Cs4[Sc6C]Cl13 (tetragonal, I41/amd; a = 1 540,5(4); c = 1 017,9(7) pm; c/a = 0,661; Z = 4; R = 0,038; Rw = 0,026 und Cs4[Pr6(C2)]I13 (a = 1 804,9(3); c = 1 259,5(3) pm; c/a = 0,698; R = 0,106; Rw = 0,068) werden bei der metallothermischen Reduktion von ScCl3 bzw. PrI3 mit Caesium in Gegenwart von Kohlenstoff in verschweißten Tantalampullen in Form von grünschwarzen bzw. blauschwarzen, messingglänzenden Einkristallen erhalten. Die weitgehend isotypen Kristallstrukturen enthalten isolierte [Sc6C]- bzw. [Pr6(C2)]-Cluster, die von 18 Halogenid-Ionen (X-, 12 Xi und 6 Xa; X = Cl bzw. I) umgeben sind. Die Verknüpfung erfolgt gemäß dem Motiv [M6Z]X8iX4/21-aX4/2a-1X2/2a-a (M = Sc bzw. Pr; Z = C bzw. C2) und stellt damit ein noch unbekanntes Verknüpfungsmuster für Verbindungen der Zusammensetzung Ax[M6Z]X13 dar, das jenem der [TiO6]-Oktaeder in der Anatas-Struktur von TiO2 entspricht.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1527-1531 
    ISSN: 0044-2313
    Keywords: Terbium Cluster ; [Tb10(C2)2] ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cs3[Tb10(C2)2]Cl21, A New Formula and Structure Type with Isolated Dimeric ClustersCs3[Tb10(C2)2]Cl21 is obtained via the metallothermic reduction of TbCl3 with caesium in the presence of graphite as black single crystals. The crystal structure (monoclinic, C2/c, Z = 4; a = 2318.72(13); b = 1245.8(9); c = 1502.0(13) pm; β = 98.13(6)°; R = 0.089; Rw = 0.049) contains dimeric clusters that are built from two octahedra connected via one common edge and filled with C2 units. These isolated [Tb10(C2)2] clusters are surrounded by 26 chloride ligands which are then connected via i - a and a - a bridges in a way that voids for Cs+ of coordination number 10 are formed.
    Notes: Cs3[Tb10(C2)2]Cl21 entsteht bei der metallothermischen Reduktion von TbCl3 mit Caesium in Gegenwart von Graphit in Form schwarzer Einkristalle. Die Kristallstruktur (monoklin, C2/c, z = 4; a = 2318,72(13); b = 1245,8(9); c = 1502,0(13) pm; β = 98,13(6)°; R = 0,089; Rw = 0,049) enthält dimere Cluster, die aus zwei über eine gemeinsame Kante verknüpften und durch zwei C2-Hanteln aufgefüllten Oktaedern gebildet werden. Die isolierten [Tb10(C2)2]-Cluster sind von insgesamt 26 Cl- umgeben und durch i - a- bzw. a - a-Brücken so miteinander verknüpft, daß für die Cs+ Lücken der Koordinationszahl 10 verbleiben.
    Additional Material: 3 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1393-1398 
    ISSN: 0044-2313
    Keywords: Rare Earth Fluorides ; Crystal Structure ; Ammonium Fluorides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Crystal Structure of NH4DyF4. Further Fluorides NH4MF4 (M = La—Tb)
    Notes: Die Fluoride NH4MF4 (M = La—Dy) entstehen bei der Umsetzung der Metalle M mit N2H6F2 bei Temperaturen zwischen 80 und 350°C in verschweißten Monelampullen. Es werden in Abhängigkeit vom Selten-Erd-Element und von der Reaktionstemperatur drei Strukturen beobachtet: Die Kristallstruktur der Form I wurde anhand von Einkristallen von NH4DyF4 aufgeklärt [orthorhombisch, Pbcm (Nr. 57), Z = 4; a = 852,10(7) pm, b = 722,54(8) pm, c = 626,28(12) pm]; die bei niedrigen Temperaturen hergestellten Fluoride NH4MF4 (M = Ce—Tb) sind isotyp. Bei höheren Temperaturen treten die Formen II [für M = La—Nd; orthorhombisch (?), Z = 8] bzw. III [M = Eu—Tb, geordnete Überstruktur zum CaF2-Typ, analog TlGdF4, tetragonal, P4/m (?), Z = 16] auf.The fluorides NH4MF4 (M = La—Dy) are obtained through the reaction of the metals M with N2H6F2 at temperatures between 80 and 350°C in sealed Monel ampoules. Dependent upon the rare-earth element M and the reaction temperature three crystal structures are observed: The crystal structure of modification I was determined from single crystal data of NH4DyF4 [orthorhombic, Pbcm (no. 57), Z = 4; a = 852.10(7) pm, b = 722.54(8) pm, c = 626.28(12) pm]; the fluorides NH4MF4 (M = Ce—Tb) obtained at fairly low temperatures are isotypic. At higher temperatures the modifications II [for M = La—Nd; orthorhombic (?), Z = 8] and III [M = Eu—Tb, ordered superstructure of the CaF2 type, analogous to TlGdF4, tetragonal, P4/m (?), Z = 16] are observed.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 200-204 
    ISSN: 0044-2313
    Keywords: Alkaline Earth ; Praseodym ; Iron Oxide ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Ba6Pr2Fe4O15, Ba5SrPr2Fe4O15 and Ba5CaPr2Fe4O15Ba6Pr2Fe4O15 (I), Ba5SrPr2Fe4O15 (II), and Ba5CaPr2Fe4O15 (III) have been prepared by high temperature CO2-LASER techniques. (I)-(III) crystallize isotypic to the Ba6Ln2Al4O15 type, space group C6v4-P63mc, (I): a = 11.808(2), c = 6.894(5), Z = 2. Typical features of the crystal structure are face shared MO6 octahedra (M = Ba or Ba/Sr, Ba/Ca) and a statistical distribution of Ba and Pr in a ratio of 1 : 2 within double capped trigonal prisms of oxygen. Fe shows tetrahedral as well as octahedral coordination by oxygen. Calculation of coulomb terms of lattice energy indicate the stabilization of Pr3+ beside Fe3+ by the Ba6Ln2Al4O15 type.
    Notes: Ba6Pr2Fe4O15 (I), Ba5SrPr2Fe4O15 (II) und Ba5CaPr2Fe4O15 (III) wurden mit Hochtemperatur-CO2-LASER-Technik dargestellt. (I)-(III) kristallisieren mit hexagonaler Symmetrie, Raumgruppe C6V4-P63mc, (I): a = 11.808(2), c = 7,036(4) Å; (II): a = 11.689(2), c = 6.954(2) Å; (III): a = 11.602(6), c = 6.894(5) Å, Z = 2. Charakteristische Eigenschaften dieser Kristallstruktur sind flächenverknüpfte MO6-Oktaeder (M = Ba oder Ba/Sr, Ba/Ca) und eine statistische Verteilung von Ba und Pr im Verhältnis 1 : 2 in einem zweifach überkappten trigonalen Sauerstoffprisma. Fe zeigt sowohl tetraedrische als auch oktaedrische Sauerstoffkoordination. Berechnungen der Coulomb-Terme zur Gitterenergie deuten an, daß durch den Ba6Ln2A4O15-Typ Pr3+ neben Fe3+ stabilisiert wird.
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 791-795 
    ISSN: 0044-2313
    Keywords: Lithium Niobium Chloride ; Niobium Cluster ; Synthesis ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zweidimensionale Netzwerke in der Struktur von Li2[Nb6Cl16]Li2[Nb6Cl16] wurde aus Nb-Pulver, NbCl5 und LiCl in Quarzglasampullen bei 700°C hergestellt. Die anhand von Einkristall-Röntgendaten verfeinerte Kristallstruktur ist orthorhombisch, Raumgruppe Cmca (Nr. 64), mit Z = 4 und Gitterkonstanten von a = 1274.7(1) pm, b = 1318.5(1) pm, c = 1341.1(2) pm. Die Verfeinerung aller Atompositionen ergab R1 = 0.031 (basierend auf F-Werten) und wR2 = 0.081 (basierend auf F2-Werten). Die Struktur enthält Schichten aus [Nb6Cl12i]2+ mit äußeren Cla-a-Liganden, die vier Ecken jedes oktaedrischen Niobclusters in Schichten verknüpfen, plus zwei terminale Cla-Liganden an jedem Niobcluster, entsprechend [Nb6Cl12iCl4/2a-aCl2a]2-. Das gleiche Verknüpfungsmuster liegt in binären Mo6X12-Halogeniden vor, die jedoch acht innere Halogenliganden besitzen (Mo6Cl8i). Gewinkelte Nb-Cla-a-Nb Brücken (159°) zwischen benachbarten Niobclustern korrespondieren mit Verdrehungen der [Nb6Cl16]2--Einheiten innerhalb der Schichten, wodurch zwei Li+ verzerrt trigonal-bipyramidale Lücken besetzen.
    Notes: Li2[Nb6Cl16] has been synthesized from the reaction of Nb powder, NbCl5 and LiCl in sealed silica tubes at 700°C. The structure, as determined by single-crystal X-ray diffraction, is orthorhombic, space group Cmca (no. 64) with Z = 4 and has lattice parameters a = 1274.7(1) pm, b = 1318.5(1) pm, c = 1341.1(2) pm. The refinement of all atomic positions yielded Rl = 0.031 (based on F values) and wR2 = 0.081 (based on F2 values). The structure contains layers formed by [Nb6Cl2i]2+ with outer Cla-a ligands that bridge four vertices of each octahedral niobium cluster into sheets, plus two terminal Cla ligands of each cluster, to be described as [Nb6Cl12iCl4/2a-aCl2a]2-. The same connectivity pattern is present for binary Mo6X12 halides, containing eight inner halide ligands (Mo6Cl8i). Non-linear Nb-Cla-a-Nb bridges (159°) correspond with intra-layer rotations of [Nb6Cl16]2 units and thereby accommodate two Li+ in distorted trigonal - bipyramidal voids.
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