bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and coordination properties of facilitated olefin transport membranes consisting of crosslinked poly(vinyl alcohol) and silver hexafluoroantimonate
Authors: Kim Jong Hak , Min Byoung Ryul , Won Jongok , Kim Chang Kon , Kang Yong Soo 
Published: January 2004

AbstractThe high selectivity of solid‐state crosslinked poly(vinyl alcohol) (CPVA) membranes containing silver hexafluoroantimonate (AgSbF6), with respect to olefin/paraffin mixtures, was previously reported. The structure and coordination properties of CPVA/AgSbF6 complexes were investigated in this study with wide‐angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), X‐ray photoelectron spectroscopy (XPS), and theoretical ab initio calculations, and they were compared with those of poly(vinyl alcohol) (PVA)/AgSbF6 complexes. Contrary to expectations, the measurements of the intersegmental d‐spacings and glass‐transition temperatures indicated that the chain mobility in the PVA/AgSbF6 membranes was lower than that in the CPVA/AgSbF6 membranes. The different extents of transient crosslinking in the two systems were attributed mostly to their different coordination structures; silver ions in PVA/AgSbF6 were coordinated with hydroxyl oxygens located near the polymer main chains, whereas those in CPVA/AgSbF6 were coordinated with aldehyde oxygens located far from the main chains. According to WAXS spectra, AgSbF6 was completely dissolved in both PVA and CPVA, and this disrupted the crystallinity of the polymers. However, our DSC study showed that the silver ions dissolved in both polymer matrices recrystallized into silver oxide at elevated temperatures. The binding energy of Ag3d5/2, as determined from XPS spectra, shifted to lower values with the addition of increasing amounts of the polymer matrix, indicating the increasing coordination of silver ions with polymer chains. The presence of various oxygen species with and without coordination to silver ions was confirmed from O1s XPS spectra of CPVA membranes containing silver ions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 621–628, 2004
Miscibility behavior and hydrogen bonding in blends of poly(vinyl phenyl ketone hydrogenated) and poly(2‐ethyl‐2‐oxazoline)
Authors: Maldonado‐Santoyo M. , Ortíz‐Estrada C. , Luna‐Bárcenas G. , Sanchez I. C. , Cesteros L. C. , Katime I. , Nuño‐Donlucas S. M. 
Published: January 2004

AbstractThe miscibility behavior of poly(2‐ethyl‐2‐oxazoline) (PEOx)/poly(vinyl phenyl ketone hydrogenated) (PVPhKH) blends was studied for the entire range of compositions. Differential scanning calorimetry and thermomechanical analysis measurements showed that all the PEOx/PVPhKH blends studied had a single glass‐transition temperature (Tg). The natural tendency of PVPhKH to self‐associate through hydrogen bonding was modified by the presence of PEOx. Partial IR spectra of these blends suggested that amide groups in PEOx and hydroxyl groups in PVPhKH interacted through hydrogen bonding. This physical interaction had a positive influence on the phase behavior of PEOx/PVPhKH blends. The Kwei equation for Tg as a function of the blend composition was satisfactorily used to describe the experimental data. Pure‐component pressure–volume–temperature data were also reported for both PEOx and PVPhKH. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 636–645, 2004
Completely biodegradable composites of poly(propylene carbonate) and short, lignocellulose fiber Hildegardia populifolia
Authors: Li X. H. , Meng Y. Z. , Wang S. J. , Rajulu A. Varada , Tjong S. C. 
Published: January 2004

AbstractThe composites of biodegradable poly(propylene carbonate) (PPC) reinforced with short Hildegardia populifolia natural fiber were prepared by melt mixing followed by compression molding. The mechanical properties, thermal properties, and morphologies of the composites were studied via static and dynamic mechanical measurements, thermogravimetric analysis, and scanning electron microscopy (SEM) techniques, respectively. Static tensile tests showed that the stiffness and tensile strength of the composites increased with an increasing fiber content. However, the elongation at break and the energy to break decreased dramatically with the addition of short fiber. The relationship between the experimental results and the compatibility or interaction between the PPC matrix and fiber was correlated. SEM observations indicated good interfacial contact between the short fiber and PPC matrix. Thermogravimetric analysis revealed that the introduction of short Hildegardia populifolia fiber led to a slightly improved thermooxidative stability of PPC. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 666–675, 2004
Thermal, crystallization, mechanical, and rheological characteristics of poly(trimethylene terephthalate)/poly(ethylene terephthalate) blends
Authors: Supaphol Pitt , Dangseeyun Nujalee , Thanomkiat Pakin , Nithitanakul Manit 
Published: January 2004

AbstractBlends of poly(trimethylene terephthalate) (PTT) and poly(ethylene terephthalate) in the amorphous state were miscible in all of the blend compositions studied, as evidenced by a single, composition‐dependent glass‐transition temperature observed for each blend composition. The variation in the glass‐transition temperature with the blend composition was well predicted by the Gordon–Taylor equation, with the fitting parameter being 0.91. The cold‐crystallization (peak) temperature decreased with an increasing PTT content, whereas the melt‐crystallization (peak) temperature decreased with an increasing amount of the minor component. The subsequent melting behavior after both cold and melt crystallizations exhibited melting point depression behavior in which the observed melting temperatures decreased with an increasing amount of the minor component of the blends. During crystallization, the pure components crystallized simultaneously just to form their own crystals. The blend having 50 wt % of PTT showed the lowest apparent degree of crystallinity and the lowest tensile‐strength values. The steady shear viscosity values for the pure components and the blends decreased slightly with an increasing shear rate (within the shear rate range of 0.25–25 s−1); those of the blends were lower than those of the pure components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 676–686, 2004
Oniom (MP2:PM3) study of C60–water complex
Authors: Fomina Lioudmila , Reyes Abraham , Guadarrama Patricia , Fomine Serguei 
Published: January 2004

AbstractThe ONIOM (MP2:PM3) model in combination with local implementation of MP2 single‐point energy evaluation was used to model the C60–water complex. In agreement with experimental data, stabilization of the complex can be described in terms of interaction between the lone electron pair of water oxygen and π*‐orbitals of fullerene with electron correlation being the most important contribution to the complex stabilization. It was found that for qualitatively correct description of C60–water complex geometry it is essential to have at least 12 carbon atoms of C60 molecule and water molecule in high MP2 ONIOM layer and use a basis set of at least 6‐31+G(d,p) quality. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Localized molecular orbitals for excited states of polyenals, polyendials, and polyenones
Authors: Pitarch‐Ruiz J. , Evangelisti S. , Maynau D. 
Published: January 2004

AbstractThe work is focused on the generation of localized molecular orbitals for excited states. A recently developed a priori method based in a CAS‐SCF–type algorithm is applied. The method generates directly localized orbitals and can be applied to multireference wavefunctions. A detailed description of the performance of the method as well as the locality of the MOs for the example of the singlet n→π* (CO) excited state is given. It is in general possible to obtain local orbitals for the doubly occupied and virtual valence orbitals. The partial delocalization of the π* (CO) orbital is discussed, as is the effect of the use of different CAS spaces. The systems under study are polyenals, polyendials, and polyenones where the π* (CO) orbital interacts with the rest of the π system. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Isolation of Amylose from Starch Solutions by Phase Separation
Authors: Kim Sanghoon , Willett Julious L. 
Published: January 2004

AbstractConventionally, fractionation of the two components of starches, amylopectin and amylose had been achieved by aqueous dispersion or aqueous leaching of granules, and selective retrogradation or alcohol precipitation of amylose. Recently, we found that starch solutions show the same phase behavior as the pseudo‐binary system polystyrene/poly(butadiene) in dioctylphthalate solution. By choosing proper temperature, concentration, and solvent medium, vertical phase separation could be induced in starch solutions. In this article, we show that construction of the phase dia‐gram of the two components of starch solutions provides us with a new simple method for isolating amylose from starch solutions.
Solid State NMR and X‐ray Studies on Amylose Complexes with Small Organic Molecules
Authors: Kawada Jumpei , Marchessault Robert H. 
Published: January 2004

AbstractCrystalline complexes of amylose with lauric acid, n‐butanol, n‐pentanol, dimethyl sulfoxide and thymol were examined by 13C CP/MAS NMR and X‐ray diffraction methods. The complexes displayed the single helix V‐amylose structure and were heat stable at least up to 90 °C. In addition, the X‐ray diffraction pattern of the amylose‐n‐butanol complex was similar to that of the amylose‐n‐pentanol complex which is interpreted to mean that the guest agents are not present in crystallographic register. It is suggested that the guests are in a matrix, of crystal surfaces, dislocations and chain folds, such that only the amylose chains contribute to the observed crystalline diffraction patterns. After humidification, the NMR spectra showed partial transformation to the double helix B‐polymorph for all complexes except that formed with lauric acid. The transformation is dependent on the alkyl chain length of guest agents. Once the double helix polymorph was formed, it was permanent unless the sample was redissolved.
NC12H8(NH)2[Gd(N3C12H8)4] und [Gd(N3C12H8)3(N3C12H9)]·PhCN: Ein Beitrag zur Reaktivität und Kristallchemie homoleptischer Selten‐Erd‐Pyridylbenzimidazolate
Authors: Müller‐Buschbaum Klaus , Quitmann Catharina C. 
Published: January 2004

AbstractFarblose, transparente Kristalle von NC12H8(NH)2[Gd(N3C12H8)4] konnten in solvensfreier Synthese durch Reaktion von Gd‐Metall mit einer 2‐(2‐Pyridyl)‐Benzimidazol‐Schmelze, sowie transparente, zartgelbe Kristalle der Verbindung [Gd(N3C12H8)3(N3C12H9)]·PhCN aus der thermalen Weiterreaktion von NC12H8(NH)2[Gd(N3C12H8)4] mit Benzonitril erhalten werden. Beide Verbindungen zeigen homoleptische, reine N‐Koordinationen nur der Pyridylbenzimidazolat‐Liganden um Gadolinium; die PhCN Moleküle koordinieren nicht. Während NC12H8(NH)2[Gd(N3C12H8)4] jedoch salzartig und aus (NC12H8(NH)2)+‐ und [Gd(N3C12H8)4]—‐Ionen aufgebaut ist, zeigt [Gd(N3C12H8)3(N3C12H9)]·PhCN einen molekularen Aufbau aus ungeladenen [Gd(N3C12H8)3(N3C12H9)]‐Einheiten.
Zur Kristallchemie der Oxoplatinate
Authors: Müller‐Buschbaum Hanskarl 
Published: January 2004

AbstractDie Kristallchemie der Oxoplatinate wird mit Blick auf die Koordination von Pt2+ und Pt4+ systematisiert. Allein Pt2+ zeigt im Festkörper eine charakteristische quadratisch planare Koordination, die es mit anderen Elementen, wie Cu2+, Pd2+, Ni2+, teilt. Relativ oft treten gemischte Valenzen (Pt2+/Pt4+) in planarer Sauerstoffkoordination auf. Außerordentlich selten ist dagegen eine hantelförmige O—Pt2+—O‐Koordination. Die Kristallchemie von Pt4+ ähnelt zahllosen oktaedrisch koordinierten Metallionen, und spielt am Aufbau der kristallinen Oxoplatinate nur gelegentlich eine erkennbare Rolle. Es gibt erstaunliche Verwandtschaften der Polyederverknüpfungsmuster bei grundsätzlich verschiedenen Zusammensetzungen, wie an den Beispielen BaLn2PtO5, Ba3Cu2Ln2PtO10, Ba5Ln8Zn4O21, Ba13Ln8Zn4Pt4O37 und Ba17Ln16Zn8Pt4O57 erläutert wird. Ferner wird gezeigt, daß Ba4Sm4Zn3PtO15 mit Ba6Nd2Al4O15 und Ba4NaCu0, 5Pt1, 5O8 mit Ba15Pt6O27 isotyp ist. An Oxoplatinaten mit Elementen, die sterisch wirksame Elektronenpaare enthalten, werden einseitig offene Polyeder beobachtet. Die Positionen der stereochemisch aktiven Elektronenpaare werden mit Berechnungen der Coulomb‐Terme der Gitterenergie ermittelt.
Neue Heteropolyanionen des Wolframs mit Vanadium(IV) als Heteroatom
Authors: Drewes D. , Limanski E. M. , Piepenbrink M. , Krebs B. 
Published: January 2004

AbstractDie Synthesen zweier neuer Heteropolyanionen mit Vanadium als Heteroatom werden vorgestellt. Sie wurden vollständig durch Röntgenstrukturanalysen sowie IR‐ und Ramanspektroskopie charakterisiert. Die Verbindung ((CH3)4N)6Na4[(VO(H2O)2)2(WO2)2(BiW9O33)2]·18H2O (1) kristallisiert im triklinen Kristallsystem (P1¯) mit a = 13, 299(3)Å, b = 13, 554(3)Å, c = 18, 620(4)Å und α = 90, 22(3)°, β = 91, 99(3)°, γ = 119, 16(3)°. Na5, 4K6, 6[(VO)3(AsW9O33)2]·29H2O (2) kristallisiert in der hexagonalen Raumgruppe P63/mmc mit den Zellkonstanten a = 15, 124(3)Å und c = 24, 209(5)Å.Das Polyanion in 1 ist isostrukturell zu Anionen des sogenannten M2X2W20‐Typs mit anderen Heteroatomen. Sie sind aus zwei β‐B‐[XW9O33]‐Fragmenten aufgebaut, die sich von Defektstrukturen des Keggin‐Anions ableiten lassen. Diese Untereinheiten sind über zwei WO2‐Gruppen zwei weitere M(H2O)3‐Gruppen (M = Übergangsmetall)verknüpft und bilden so den M2X2W20‐Typ aus. Das Anion in 2 ist ein neuer Vertreter des M3X2W18‐Typs, in dem zwei α‐B‐[XW9O33]‐Einheiten über einen Ring aus drei Übergangsmetallatomen verknüft sind.
The Nature of the Colour Centres in ‘Maya Blue’ — the Incorporation of Organic Pigment Molecules into the Palygorskite Lattice
Authors: Reinen D. , Köhl P. , Müller C. 
Published: January 2004

AbstractIt is shown by optical spectroscopy that indigo molecules, most likely incorporated into the channels of the palygorskite host structure, are the solely colour centres in the ancient Maya Blue pigment — in use during the Maya cultural period in Yucatan and Guatemala. This study also shows that the blue colour of solid indigo shifts toward turquoise and greenish hues when fastened to the host; it is suggested that the corresponding spectral modifications originate from the energy when single indigo molecules undergo hydrogen bonding with the hydroxy‐groups in the channels (or in the open channels on the surface). Indeed artefacts from the Maya culture exhibit rather greenish than pure blue colours.Similarly a tetrachloro‐derivative of thioindigo forms hydrogen bonds with palygorskite, as evidenced by an again distinct colour change from red‐violet to blueish‐violet. Bulkier pigment molecules bearing hydroxy‐groups, such as anthrachinon derivatives, seem to directly react with the host surface, but without producing very significant colour shifts.
[Mn(H2O)2]4[HNC5H4(COO)]2[C6H2(COO)4]2·4H2O — Ein dreidimensionales Koordinationspolymer mit Gastwassermolekülen in kanalartigen Hohlräumen
Authors: Köferstein Roberto , Robl Christian 
Published: January 2004

AbstractEinkristalle von [Mn(H2O)2]4[HNC5H4(COO)]2[C6H2(COO)4]2·4H2O wurden in wässeriger Lösung bei 55 °C erhalten. Raumgruppe P1¯ (Nr. 2), a = 999.7(2), b = 1314.4(2), c = 1645.8(2) pm, α = 101.096(8)°, β = 92.796(14)°, γ = 96.03(2)°, V = 2.1053(5) nm3, Z = 2. Die vier kristallographisch unabhängigen Mn2+ sind verzerrt oktaedrisch von zwei Wassermolekülen, drei Sauerstoffatomen der Pyromellitatanionen und einem Sauerstoffatom aus dem Isonicotinsäuremolekül umgeben (Mn—O 208.6(2) — 227.3(3) pm). Aus der Verbindung von Mn2+ mit [C6H2(COO)4]4— resultiert ein dreidimensionales Koordinationspolymer mit zwei unterschiedlichen kanalartigen Hohlräumen, die sich entlang [110] erstrecken und einerseits von Wassermolekülen sowie andererseits durch Isonicotinsäuremoleküle ausgefüllt werden. Bei der thermogravimetrischen Untersuchung an Luft erfolgte die Kristallwasserabgabe in zweiStufen zwischen 97 und 200 °C. Das Anhydrid war zwischen 200 und 340 °C stabil. Die weitere Zersetzung führte zu Mn3O4.
Präparation und Charakterisierung von PbBr2·C4H10O3 (Diethylenglykol)
Authors: Oldag Thorsten , Keller Hans‐Lothar 
Published: January 2004

AbstractStructural Chemistry of PbBr2·C4H10O3 (Diethyleneglycol)Crystals of PbBr2·C4H10O3 have been synthesized and structurally characterized by single‐crystal X‐ray diffraction. PbBr2·C4H10O3 crystallizes monoclinic in space group P21/n (No. 14) with a = 9.370(1)Å, b = 10.045(1)Å, c = 21.090(1)Å, β = 98.98(1)° and Z = 8.The compound contains compact Pb—Br groups, which build colums parallel to [0 1 0] direction by Hydrogen Bonding.
Raman Investigation of the Low Temperature Phase Transitions in Monoclinic TlReO4
Authors: de Waal Danita , Kiefer Wolfgang 
Published: January 2004

AbstractThe Raman spectrum of monoclinic TlReO4 is presented together with a factor group analysis and assignment of the bands. The phase transitions of monoclinic TlReO4 is investigated below room temperature, and two phase transitions were identified between room temperature and 90 K. The room temperature monoclinic phase was converted to the orthorhombic phase at 170 K upon cooling, and to the tetragonal phase at 150 K. Upon heating back to room temperature the tetragonal phase persisted until the orthorhombic phase could be identified at 210 K and 220 K. From 230 K to room temperature the monoclinic phase could again be observed.
Structure and Bonding of the Mixed‐Valent Platinum Trihalides, PtCl3 and PtBr3
Authors: von Schnering Hans Georg , Chang Jen‐Hui , Freiberg Maria , Peters Karl , Peters Eva‐Maria , Ormeci Alim , Schröder Liane , Thiele Gerhard , Röhr Caroline 
Published: January 2004

AbstractThe isotypical crystal structures of the mixed valent trihalides PtCl3 and PtBr3 were redetermined by single crystal methods (space group R3¯; trigonal setting; PtCl3: a = 21.213Å, c = 8.600Å, c/a = 0.4054; Z = 36; 1719 hkl; R = 0.035; PtBr3: a = 22.318Å, c = 9.034Å; c/a = 0.4048; Z = 36; 1606 hkl; R = 0.027). A cubic closest packing of X— anions forms the basis of an optimized arrangement of cuboctahedrally [Pt6X12] cluster molecules with PtII and enantiomers of helical chains of edge‐condensed [PtX2X4/2] octahedra with PtIV in cis‐Δ‐ and cis‐Λ‐configuration, respectively. The bond lengths vary with the function of the X— ligands (d¯(PtII—X) = 2.315 and 2.445Å; d¯(PtII—PtII) = 3.336 and 3.492Å; d(PtIV—X) = 2.286 — 2.417Å and 2.437 — 2.563Å). The PtII atoms are shifted outwards the X12 cuboctahedra by 0.045Å and 0.024Å, respectively. The symmetry governed Periodic Nodal Surface, PNS, perfectly separates the regions of different valencies. Quantum chemical calculations exclude the possible additional interactions between PtII and one of the exo‐ligands of PtIV.
Synthese und Kristallstruktur der Monoammoniakate von Lithiumhalogeniden: LiBr·NH3 und LiI·NH3
Authors: Jacobs Herbert , Friedriszik Martin 
Published: January 2004

AbstractFür röntgenographische Strukturbestimmungen geeignete Kristalle von LiBr·NH3 und von LiI·NH3 wurden durch Umsetzung von Li mit NH4Br bzw. LiH mit NH4I bei 523 K bzw. 423 K in Autoklaven erhalten. An Kristallen ermittelte Zellparameter sind:LiBr·NH3: P21/n, a = 7, 077(2)Å, b = 7, 026(2)Å, c = 7, 490(2)Å β = 114, 84(3)°, Z = 4LiI·NH3: P21, a = 4, 493(1)Å, b = 6, 077(1)Å, c = 7, 512(2)Å β = 107, 15(3)°, Z = 2Die Ammoniakate sind unterschiedlich aufgebaut. Beide enthalten Schichten verknüpfter Tetraeder Li(NH3)X3/3 mit X = Br, I. Beim Bromid treten Tetraederdoppeleinheiten mit einer Br‐Br Kantenverknüpfung auf, während beim Iodid alle Tetraeder ausschließlich über Iodatome zu gewellten Schichten eckenverknüpft sind. IR‐ und Raman‐spektroskopische Messungen zeigen, dass schwache H‐Brücken N‐H···X vorliegen und dass die NH3‐Liganden bei Raumtemperatur lagefixiert sind.
Alkalimetallbismutide ABi und ABi2 (A = K, Rb, Cs) — Synthesen, Kristallstrukturen, Eigenschaften
Authors: Emmerling Franziska , Längin Nina , Petri Denis , Kroeker Martin , Röhr Caroline 
Published: January 2004

AbstractDie Zintlphasen ABi (A = K/Rb/Cs; monoklin, Raumgruppe P21/c, a = 1422.3(2)/1474.2(2)/1523.7(3), b = 724.8(1)/750.2(1)/773.7(1), c = 1342.0(2)/1392.1(2)/1439.9(2) pm und β = 113.030(3)/113.033(2)/112.722(3)°, Z = 16) kristallisieren im β‐CsSb Strukturtyp und enthalten Ketten zweibindiger Bi—‐Atome. Es handelt sich damit und nach den berechneten elektronischen Strukturen um Halbleiter mit kleinen Bandlücken von ca. 0.5 eV. Dagegen sind die Phasen ABi2 (A = K/Rb/Cs; kubisch, Raumgruppe Fd3¯m, a = 952.1(2)/962.4(8)/972.0(3) pm, Z = 8) Laves‐Phasen und zeigen entsprechend typische metallische elektronische Leitfähigkeiten und keine Bandlücken.
Synthese von dreidimensional geordneten Einlagerungsverbindungen des Hectorits
Authors: Breu Josef , Seidl Wolfgang , Senker Jürgen 
Published: January 2004

AbstractDurch die Einlagerung großer kationischer Abstandshalter wie 1, 4‐Dimethyl‐1, 4‐diazabicyclo[2.2.2]oktan (DDABCO2+) in synthetischen Cs‐Fluorohectorit wurde ein mikroporöses Material („pillared clay”︁) hergestellt. Dieser Kationenaustausch verläuft unter geeigneten Bedingungen vollständig und unter Phasenerhalt. Ausgehend von einem dreidimensional (3D) geordneten [1], ladungshomogenen [2] Cs‐Hectorit ist es so zum ersten Mal gelungen, eine einkristalline und 3D geordnete Einlagerungsverbindung eines Smectits zu synthetisieren und über Einkristallstrukturverfeinerung strukturell zu charakterisieren ([DDABCO0.25]zwi[Mg2.5Li0.5]okt[Si4]tetO10F2 , monoklin, C2/m, a = 5.2635(9) Å, b = 9.1278(14) Å, c = 13.984(3) Å, β = 96.89 (2)°, V = 667.0(2) Å3, Z = 2). Die organischen Zwischenschichtkationen überbrücken, ähnlich wie Cs+ in der Ausgangsverbindung, den Zwischenschichtraum in definierter Weise, indem sie auf beiden Seiten in die Vertiefungen der Silicatoberfläche greifen und die hexagonalen Kavitäten genau gegenüber anordnen. Die Zwischenschichtkationen sind dabei mit ihrer C3‐Achse in der Ebene der Zwischenschicht orientiert.
Synthesis and Crystal Structure of the Hydrogen Polyphosphide Bis(Tetraphenylphosphonium) hydrogenheptaphosphide‐ammonia(1/3) (PPh4)2HP7 · 3NH3
Authors: Aschenbrenner Jürgen C. , Korber Nikolaus 
Published: January 2004

Abstract(PPh4)2HP7 · 3NH3 was prepared by the reaction of K3P7 with a proton‐charged ion exchange resin in the presence of (PPh4)Br in liquid ammonia, and characterized by low temperature X‐ray structure analysis. The thermally very unstable compound contains the hydrogenheptaphosphide anion HP, the nortricyclane‐like cage of which is slightly distorted by the attachment of the hydrogen atom.
A disordered microstructure material model based on fractal geometry and fractional calculus
Authors: Carpinteri A. , Chiaia B. , Cornetti P. 
Published: January 2004

AbstractFractal patterns often arise in the failure process of materials with a disordered microstructure. It is shown that they are responsible of the size effects on the parameters characterizing the material behaviour in tensile tests (i.e. the strength, the fracture energy, and the critical displacement). Based on fractal geometry, a simple model of a generic disordered material is set. The physical quantities describing the stress‐strain state of such fractal medium are pointed out. They show anomalous (non integer) physical dimensions. In terms of these fractal quantities, it is possible to define a fractal cohesive law, i.e. a constitutive law describing the tensile failure of an heterogeneous material, which is scale invariant. Then we propose new mathematical operators from fractional calculus to handle the fractal quantities previously introduced. In this way, the static and kinematic (fractional) differential equations of the model are pointed out. These equations form the basis of the mechanics of fractal media. In this framework, the principle of virtual work is also obtained.