bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Crystal Structure of Bis(methyltriethylammonium) Hexabromotellurate(IV)‐tris{dibromodiselenate(I)}, [NMeEt3]2n[TeBr6(Se2Br2)3]n, Containing a Chain‐Polymeric Mixed‐valence Bromotellurate(IV)‐Selenate(I) Anion
Authors: Janickis Vitalijus , Herberhold Max , Necas Marek , Milius Wolfgang
Published: June 2004

Red crystals of [NMeEt3]2n[TeBr6(Se2Br2)3]n (1) were isolated when selenium and bromine (1:1) were allowed to react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriethylammonium bromide (1:2). The salt 1 crystallizes in the monoclinic space group C2/c with the cell dimensions a = 27.676(6) Å, b = 9.665(2) Å, c = 18.796(4) Å and ß = 124.96(3)° (120 K). The [TeBr6(Se2Br2)3]2— anions contain nearly regular octahedral [TeBr6]2— ions which are incorporated into a polymeric chain by bonding contacts between 3 facial bromo ligands and 3 Se2Br2 molecules, one of which is situated on the twofold symmetry axis. The distances between the μBr ligands and the SeI atoms of the Se2Br2 molecules are observed in the range 3.308(2) — 3.408(2) Å and can tentatively be interpreted as donor‐acceptor bonds with μBr as donors and Se2Br2 as acceptors. The TeIV—Br distances are in the range 2.669(1) — 2.687(1) Å. The bond lengths in the connecting Se2Br2 molecules are: SeI—SeI = 2.267(2) and 2.281(2) Å, SeI—Br = 2.340(1), 2.353(1) and 2.337(1) Å.
Alkali Metal Compounds of Hydroquinone: Synthesis and Crystal Structure
Authors: Couhorn U. , Dronskowski R.
Published: June 2004

A number of novel routes to the alkali metal compounds of hydroquinone M2[p‐C6H4O2] (M = Li, Na, K, Rb, Cs) and M[p‐C6H4O(OH)] (M = K, Rb, Cs) have been synthetically explored. The selective synthesis of the alkali 4‐hydroxyphenolates and 1, 4‐phenylenediolates is based on optimized reaction conditions (solvents, temperatures).

All compounds were structurally characterized by means of powder X‐ray diffraction using Rietveld profile refinement including C—C and C—O bond distance restraints. The atomic arrangement of M2[p‐C6H4O2](M = Na, K) (tetragonal, space group: P42/ncm) is characterized by infinite pillars of [M2[3]O2[3]]‐units along the c axis connected by [p‐C6H4O2]2—‐anions with stacking direction along c. The coordinatively unsaturated alkali metals, surrounded by three oxygen atoms, exhibit symmetrical (K) as well as asymmetrical (Na) interactions with the phenylene rings. M[p‐C6H4O(OH] (M = K, Rb) (tetragonal, space group: P4/n) forms hydrogen‐bridged linear chains of [p‐C6H4O(OH)]—‐anions along the c direction. The phenylene planes of neighboring chains have an almost orthogonal arrangement while the interchain planes are parallel. K and Rb are fourfold coordinated by two different oxygen coordination spheres.
Preparation, Thermal Behaviour and Crystal Structure of the Basic Mercury(II) Tetraoxotellurate(VI), Hg2TeO5, and Redetermination of the Crystal Structure of Mercury(II) Orthotellurate(VI), Hg3TeO6
Authors: Weil Matthias
Published: June 2004

Single crystals of Hg2TeO5 were obtained as dark‐red parallelepipeds by reacting stoichiometric amounts of Hg(NO3)2 · H2O and H6TeO6 under hydrothermal conditions (250 °C, 10d). The crystal structure (space group Pna21, Z = 4, a = 7.3462(16), b = 5.8635(12), c = 9.969(2)Å, 1261 structure factors, 50 parameters, R[F2 > 2σ(F2)] = 0.0295) is characterized by corner‐sharing [TeO6] octahedra forming isolated chains [TeO4/1O2/2] which extend parallel to [100]. The two crystallographically independent Hg atoms are located in‐between the chains and interconnect the chains via common oxygen atoms. Amber coloured single crystals of Hg3TeO6 were prepared by heating a mixture of Hg, HgO and TeO3 together with small amounts of HgCl2 as mineralizer in an evacuated and sealed silica glass tube (520 °C). The previously reported crystal structure has been re‐investigated by means of single crystal X‐ray data which reveal a symmetry reduction from Ia3¯d to Ia3¯ (Z = 16, a = 13.3808(6) Å, 609 structure factors, 33 parameters, R[F2 > 2σ(F2)] = 0.0221). The crystal structure is made up of a body‐centred packing of [TeO6] octahedra with the Hg atoms situated in the interstices of this arrangement. Upon heating, both title compounds decompose in a one‐step mechanism under formation of TeO2 and loss of the appropriate amounts of elementary mercury and oxygen.
Polysulfonylamine. CLXII [1] Kristallstrukturen von Metall‐di(methansulfonyl)amiden. 11 [2] Das dreidimensionale Koordinationspolymer K[(CH3SO2)2N] II: Eine chirale Struktur mit vier unabhängigen Formeleinheiten, Pseudozentrosymmetrie der Kristallpackung und Konformationsisomorphie des Anions
Authors: Moers Oliver , Blaschette Armand , Jones Peter G.
Published: June 2004

Von Kalium‐dimesylamid, K[(CH3SO2)2N] (KA), wurden bei Raumtemperatur aus unterschiedlichen Medien zwei monokline Modifikationen isoliert und bei —100 °C durch Einkristall‐Röntgenbeugung charakterisiert. In der zuvor veröffentlichten zentrosymmetrischen Struktur von KA I (P21/c, Z′ = 1) liegt das Anion in einer extrem seltenen Konformation der Punktgruppe C1 vor, während die chirale Struktur von KA II (P21, Z′ = 4) drei unabhängige Anionen mit normaler C2‐Symmetrie und ein weiteres mit erheblicher C1‐Verformung aufweist. Außerdem stehen im Kristall von KA II die Ionen paarweise über ein Pseudoinversionszentrum miteinander in Beziehung, so daß der Packung die Pseudosymmetrie P21/c mit Z′ = 2 zukommt. Beide Modifikationen bilden dreidimensionale Koordinationspolymere, in welchen jedes der fünf unabhängigen Anionen alle Sauerstoffatome und das Stickstoffatom in κ1‐ oder μ2‐Bindungen zu fünf oder sechs Kationen einbringt und hierbei ein jeweils anderes Konnektivitätsmuster aufbaut. Die Koordinationspolyeder der Kationen beruhen in KA I auf einer (O6N)‐Umgebung, die einem verzerrten Oktaeder mit einer zweifach besetzten Ecke nahekommt, in KA II auf zwei (O7)‐Sphären in Form von einfach überdachten verzerrten Oktaedern und zwei (O4N2)‐Sphären mit trigonal‐prismatischer Geometrie. Demnach weist die aus vier unabhängigen Formeleinheiten bestehende Struktur von KA II sowohl Konformations‐ als auch Koordinationsisomorphie auf, während das Strukturpaar KA I/KA II einen Fall von gleichzeitig auftretender Konformations‐ und Koordinationsdimorphie darstellt. In beiden Strukturen existieren schwache Wasserstoffbrücken des Typs C—H···O.
A System for Tracking Down Hydrogen Positions in Crystal Structures
Authors: Hirsch Tomas K.
Published: June 2004

Hydrogen conformations in [Ta6Br12(H2O)6]X2 · trans — [Ta6Br12(OH)4(H2O)2] · 18H2O (X = Cl or Br), [Ta6Br12(H2O)6]8 · (ZnBr4)8 · 96H2O, Na6[RuO2{TeO4(OH)2}2] · 16H2O, and Na5[Ag{TeO4(OH)2}2] · 16H2O were modeled from a set of simple rules. The systems are quite complex, but subsequent energy optimizations show that it is possible to make quite good predictions of where the hydrogen atoms are situated.
New Mixed Ligand Copper(II) Complexes: Syntheses and Crystal Structures of Cu(Imid)2(H2O)L with Imid = Imidazole, L = Succinic and Fumaric Anions
Authors: Zheng Yue‐Qing , Lin Jian‐Li , Ying Er‐Bo
Published: June 2004

Reactions of freshly prepared Cu(OH)2—2x(CO3)x · yH2O and imidazole (Imid) with succinic acid and fumaric acid, respectively, in CH3OH/H2O yields Cu(Imid)2(H2O)L with L = (C4H4O4)2— (1) and (C4H2O4)2— (2). Both isostructural complexes consist of 1D [Cu(Imid)2(H2O)L2/2] polymeric chains, in which the T‐shaped [Cu(Imid)2(H2O)]2+ moieties are bridged by bis‐monodentate dicarboxylato ligands. Through the interchain hydrogen bonds between the coordinating H2O molecule and the non‐coordinating carboxylate O atom, the polymeric chains are assembled into 2D layers, which are further assembled via interlayer N—H···O hydrogen bonds between imidazole N atom and the coordinating carboxylato O atom. Thermal analyses of 1 under N2 stream showed that dehydration is immediately followed by decomposition of the anhydrous “Cu(Imid)2(C4H4O4)” intermediate into imidazole and “Cu(C4H4O4)”. Upon further heating, sublimation of imidazole is followed by dissociation of the resulting “Cu(C4H4O4)” into CO, CO2, C2H4 in gaseous phase and solid CuO as residue. Crystal data: (1) C2/c (no. 15), a = 13.712(2), b = 5.589(1), c = 17.517(2)Å, β = 105.76(1)°, U = 1292.0(3)Å3, Z = 4; (2) C2/c (no. 15), a = 13.758(2), b = 5.501(1), c = 17.464(2)Å, β = 106.05(2)°, U = 1270.2(3)Å3, Z = 4.
Ligand Substitution Reactions on Aquapentachloro‐ and Hexachloroplatinic Acid — Synthesis and Characterization of Tetrachloroplatinum(IV) Complexes with Heterocyclic N, N Donors
Authors: Gaballa Akmal , Wagner Christoph , Schmidt Harry , Steinborn Dirk
Published: June 2004

Reactions of aquapentachloroplatinic acid, (H3O)[PtCl5(H2O)]·2(18C6)·6H2O (1) (18C6 = 18‐crown‐6), and H2[PtCl6]·6H2O (2) with heterocyclic N, N donors (2, 2′‐bipyridine, bpy; 4, 4′‐di‐tert‐butyl‐2, 2′‐bipyridine, tBu2bpy; 1, 10‐phenanthroline, phen; 4, 7‐diphenyl‐1, 10‐phenanthroline, Ph2phen; 2, 2′‐bipyrimidine, bpym) afforded with ligand substitution platinum(IV) complexes [PtCl4(N∩N)] (N∩N = bpy, 3a; tBu2bpy, 3b; Ph2phen, 5; bpym, 7) and/or with protonation of N, N donor yielding (R2phenH)2[PtCl6] (R = H, 4a; Ph, 4b) and (bpymH)+ (8). With UV irradiation Ph2phen and bpym reacted with reduction yielding platinum(II) complexes [PtCl2(N∩N)] (N∩N = Ph2phen, 6; bpym, 9). Identities of all complexes were established by microanalysis as well as by NMR (1H, 13C, 195Pt) and IR spectroscopic investigations. Molecular structures of [PtCl4(bpym)]·MeOH (7) and [PtCl2(Ph2phen)] (6) were determined by X‐ray diffraction analyses. Differences in reactivity of bpy/bpym and phen ligands are discussed in terms of calculated structures of complexes [PtCl5(N∩N)]— with monodentately bound N, N ligands (N∩N = bpy, 10a; phen, 10b; bpym, 10c).
Trans‐bis(saccharinato)cadmium(II) Complexes with 2‐Pyridylethanol: Synthesis, Crystal Structures, Spectral and Thermal Characterization of [Cd(sac)2(pyet)2] and [Cd(sac)2(H2O)(dmso)(pyet)]
Authors: Yilmaz Veysel T. , Hamamci Sevim , Thöne Carsten
Published: June 2004

Two trans saccharinate (sac) complexes of cadmium(II) with 2‐pyridylethanol (pyet) were synthesized and characterized by elemental analyses, FT—IR spectroscopy, thermal analysis and single crystal X‐ray diffractometry. The [Cd(sac)2(pyet)2] (1) and [Cd(sac)2(H2O)(dmso)(pyet)] (2) complexes crystallize in the monoclinic (P21/c) and orthorhombic [P212121] crystal systems, respectively. The sac ligands in both complexes are N‐coordinated and located in trans positions, while the pyet molecules act as a bidentate N‐ and O‐donor ligand forming two six‐membered chelate rings. Thermal decomposition of the complexes in air results in elimination of aqua, dmso and pyet ligands, respectively, forming cadmium saccharinate as a stable intermediate, which also decomposes at higher temperatures to give cadmium oxide.
Sclerosing Rhabdomyosarcoma in Childhood: Case Report and Review of the Literature
Authors: Vadgama Bhumita , Sebire Neil James , Malone Marian , Ramsay Alan Drummond
Published: June 2004

Rhabdomyosarcoma is the most common soft tissue malignancy in children but is rare in adults. The latest World Health Organization classification of soft tissue tumors recognizes embryonal, alveolar, and pleomorphic rhabdomyosarcomas. More recently, a sclerosing variant of rhabdomyosarcoma has been recognized and reported in seven adult patients. We describe a pediatric case of sclerosing rhabdomyosarcoma presenting as a sacral mass in a 3-year-old girl. Morphologically, the tumor showed a prominent sclerosing hyaline matrix and demonstrated pseudovascular and microalveolar architectural foci. Focal positivity was seen with desmin, smooth muscle actin, and myogenin. MyoD1 showed uniform diffuse nuclear staining. Fusion transcripts were not demonstrated by reverse transcriptase-polymerase chain reaction analysis. The histology, immunohistochemistry, and molecular genetics matched those reported in the seven adult cases of sclerosing rhabdomyosarcoma. This is the first case report, to our knowledge, of this rare tumor arising in the pediatric age group, and we compare the features with those reported in adult sclerosing rhabdomyosarcoma.
Schlussfolgerndes Denken - SDV
Authors: Spiel Christiane , Glück Judith , Gößler Heimo
Published: June 2004

Zusammenfassung. Der vorliegende Beitrag beschreibt theoretische Grundlagen, Entwicklung und erste Ergebnisse zum “Leistungsprofiltest Schlussfolgerndes Denken - Verbal (SDV)“. Piagets Entwicklungstheorie bildete den konzeptuellen Rahmen für die Entwicklung des SDV. Nach Befunden aus der Performanz-Kompetenz-Forschung wird der Übergang vom konkret-operatorischen zum formal-operatorischen Denken durch Moderatorvariablen beeinflusst und erfolgt in kleineren Schritten als von Piaget angenommen. Hypothesen zu Übergangsstadien werden in der Arbeit abgeleitet. Das Untersuchungsmaterial des SDV besteht aus konditionalen Syllogismen, die theoriegeleitet systematisch variiert wurden. Die Prüfung der theoretischen Annahmen erfolgte an einer Stichprobe von 418 Gymnasialschülerinnen und -schülern der 7. bis 12. Schulstufe. Die Anwendung von Mixed-Rasch Models (MRMs) auf den Datensatz ergab, dass eine 3-Klassen-Lösung, welche die formulierten Hypothesen bestätigt, die Daten am besten repräsentiert. Die drei Klassen können nach dem Leistungsprofil als konkret-operatorisches Stadium, Übergangsstadium 1 und Übergangsstadium 2 bezeichnet werden. Die durchgeführten Analysen bestätigen die theoretische Einbettung und Absicherung des SDV.
Innovationsklima - Konstruktion und erste psychometrische Überprüfung eines Messinstrumentes
Authors: Kauffeld Simone , Jonas Eva , Grote Sven , Frey Dieter , Frieling Ekkehart
Published: June 2004

Zusammenfassung. Der Fragebogen zum Innovationsklima (INNO) wurde entwickelt, um das Klima für Innovationen in Organisationen messbar zu machen. Der Fragebogen besteht aus insgesamt 21 Items, die in weniger als 10 Minuten beantwortet werden können. Mit Hilfe von Faktorenanalysen (N = 372 Mitarbeiter) wurde die Struktur des INNO auf vier Faktoren festgelegt: (1) Aktivierende Führung, (2) Kontinuierliche Reflexion, (3) Konsequente Implementation und (4) Professionelle Dokumentation. Im Hinblick auf Kriteriumsvariablen der (1) Produkt- und (2) Prozessinnovationen, (3) Unternehmensentwicklung, (4) der Anzahl der Verbesserungsvorschläge, (5) der Bewertung von Optimierungssitzungen durch die Teilnehmer, (6) der Güte der in der Gruppendiskussion erarbeiteten Lösungen und (7) des wahrgenommenen Vorgesetztenverhaltens besitzt der INNO eine befriedigende Kriteriumsvalidität. Im Sinne der diskriminanten Validität präsentieren sich die INNO-Faktoren unkorreliert mit (berufsbezogenen) Persönlichkeitsmerkmalen. Zusammenfassend ermöglicht der INNO, der hinsichtlich zentraler Gütekriterien überprüft wurde, die standardisierte und ökonomische Erfassung des Innovationsklimas.
Sea surface height determination in the Arctic Ocean from ERS altimetry
Authors: Peacock Neil R. , Laxon Seymour W.
Published: June 2004

Accurate sea surface height measurements have been extracted from ERS altimeter data in sea ice–covered regions for the first time. The data have been used to construct a mean sea surface of the Arctic Ocean between the latitudes of 60°N and 81.5°N based on 4 years of ERS‐2 data. An RMS value for the crossover differences of mean sea surface profiles of 4.2 cm was observed in the ice‐covered Canada Basin, compared with 3.8 cm in the ice‐free Greenland‐Iceland‐Norwegian Seas. Comparisons are made with an existing global mean sea surface (OSUMSS95), highlighting significant differences between the two surfaces in permanently ice‐covered seas. In addition, we present the first altimeter‐derived sea surface height variability map of the Arctic Ocean. Comparisons with a high‐resolution coupled ocean–sea ice general circulation model reveal a good qualitative agreement in the spatial distribution of variability. Quantitatively, we found that the observed variability was on average a factor of 3–4 greater than model predictions.
Influence of rain on air‐sea gas exchange: Lessons from a model ocean
Authors: Ho David T. , Zappa Christopher J. , McGillis Wade R. , Bliven Larry F. , Ward Brian , Dacey John W. H. , Schlosser Peter , Hendricks Melissa B.
Published: June 2004

Rain has been shown to significantly enhance the rate of air‐water gas exchange in fresh water environments, and the mechanism behind this enhancement has been studied in laboratory experiments. In the ocean, the effects of rain are complicated by the potential influence of density stratification at the water surface. Since it is difficult to perform controlled rain‐induced gas exchange experiments in the open ocean, an SF6 evasion experiment was conducted in the artificial ocean at Biosphere 2. The measurements show a rapid depletion of SF6 in the surface layer due to rain enhancement of air‐sea gas exchange, and the gas transfer velocity was similar to that predicted from the relationship established from freshwater laboratory experiments. However, because vertical mixing is reduced by stratification, the overall gas flux is lower than that found during freshwater experiments. Physical measurements of various properties of the ocean during the rain events further elucidate the mechanisms behind the observed response. The findings suggest that short, intense rain events accelerate gas exchange in oceanic environments.
Impacts of biomass burning in Southeast Asia on ozone and reactive nitrogen over the western Pacific in spring
Authors: Kondo Y. , Morino Y. , Takegawa N. , Koike M. , Kita K. , Miyazaki Y. , Sachse G. W. , Vay S. A. , Avery M. A. , Flocke F. , Weinheimer A. J. , Eisele F. L. , Zondlo M. A. , Weber R. J. , Singh H. B. , Chen G. , Crawford J. , Blake D. R. , Fuelberg H. E. , Clarke A. D. , Talbot R. W. , Sandholm S. T. , Browell E. V. , Streets D. G. , Liley B.
Published: June 2004

Aircraft measurements of ozone (O3) and its precursors (reactive nitrogen, CO, nonmethane hydrocarbons) were made over the western Pacific during the Transport and Chemical Evolution Over the Pacific (TRACE‐P) campaign, which was conducted during February–April 2001. Biomass burning activity was high over Southeast Asia (SEA) during this period (dry season), and convective activity over SEA frequently transported air from the boundary layer to the free troposphere, followed by eastward transport to the sampling region over the western Pacific south of 30°N. This data set allows for systematic investigations of the chemical and physical processes in the outflow from SEA. Methyl chloride (CH3Cl) and CO are chosen as primary and secondary tracers, respectively, to gauge the degree of the impact of emissions of trace species from biomass burning. Biomass burning is found to be a major source of reactive nitrogen (NOx, PAN, HNO3, and nitrate) and O3 in this region from correlations of these species with the tracers. Changes in the abundance of reactive nitrogen during upward transport are quantified from the altitude change of the slopes of the correlations of these species with CO. NOx decreased with altitude due to its oxidation to HNO3. On the other hand, PAN was conserved during transport from the lower to the middle troposphere, consistent with its low water solubility and chemical stability at low temperatures. Large losses of HNO3 and nitrate, which are highly water soluble, occurred in the free troposphere, most likely due to wet removal by precipitation. This has been shown to be the major pathway of NOy loss in the middle troposphere. Increases in the mixing ratios of O3 and its precursors due to biomass burning in SEA are estimated using the tracers. Enhancements of CO and total reactive nitrogen (NOy), which are directly emitted from biomass burning, were largest at 2–4 km. At this altitude the increases in NOy and O3 were 810 parts per trillion by volume (pptv) and 26 parts per billion by volume (ppbv) above their background values of 240 pptv and 31 ppbv, respectively. The slope of the O3‐CO correlation in biomass burning plumes was similar to those observed in fire plumes in northern Australia, Africa, and Canada. The O3 production efficiency (OPE) derived from the O3‐CO slope and NOx/CO emission ratio (ER) is shown to be positively correlated with the C2H4/NOx ER, indicating that the C2H4/NOx ER is a critical parameter in determining the OPE. Comparison of the net O3 flux across the western Pacific region and total O3 production due to biomass burning in SEA suggests that about 70% of O3 produced was transported to the western Pacific.
Mechanisms of convection‐induced modulation of passive tracer interhemispheric transport interannual variability
Authors: Lintner Benjamin R. , Gilliland Alice B. , Fung Inez Y.
Published: June 2004

Interannual variations of tropical convection impact atmospheric circulation and influence year‐to‐year variations of the transport of trace constituents in the troposphere. This study examines how two modes of convective variability, anomalous intensification and meridional displacement of centers of tropical convection, impact interhemispheric transport (IHT) interannual variability. Two modeling frameworks are employed, an atmospheric general circulation model (AGCM) and a chemical transport model (CTM) forced with a realistic, interannually varying circulation field, to investigate the zonally averaged and regional‐scale influences of the modes of convective variability on passive tracer IHT. Both convective modes are found to modulate IHT interannual variability. While convective displacement appears to be the more quantitatively significant mode within the AGCM framework, anomalous convective intensity and displacement are of equal importance in the CTM framework. The results suggest that the modeling of atmospheric tracer transport interannual variability requires accurate representation of multiple aspects of convective variability.
Biomass‐burning particle measurements: Characteristic composition and chemical processing
Authors: Hudson Paula K. , Murphy Daniel M. , Cziczo Daniel J. , Thomson David S. , de Gouw Joost A. , Warneke Carsten , Holloway John , Jost Hans‐Jürg , Hübler Gerd
Published: June 2004

The NOAA Lockheed Orion WP‐3D aircraft intercepted a forest fire plume over Utah on 19 May 2002 during the Intercontinental Transport and Chemical Transformation (ITCT) mission. Large enhancements in acetonitrile (CH3CN), carbon monoxide (CO) and particle number were measured during the fire plume interception. In the 100 s plume crossing, the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument acquired 202 positive mass spectra from ionizing single particles in the 0.2–5 μm size range. These particles contained carbon, potassium, organics, and ammonium ions. No pure soot particles were sampled directly from the plume. By characterizing these particle mass spectra, a qualitative biomass‐burning particle signature was developed that was then used to identify biomass‐burning particles throughout ITCT. The analysis was extended to identify biomass‐burning particles in four other missions, without the benefit of gas‐phase biomass‐burning tracers. During ITCT, approximately 33% of the particles sampled in the North American troposphere and 37% of the particles transported from Asia, not influenced by North American sources, were identified as biomass‐burning particles. During the WB‐57 Aerosol Mission (WAM), Atmospheric Chemistry of Combustion Emissions near the Tropopause (ACCENT) and ACCENT 2000 missions, 7% of stratospheric particles were identified as biomass‐burning particles. During the Cirrus Regional Study of Tropical Anvils and Cirrus Layers – Florida Area Cirrus Experiment (CRYSTAL‐FACE) this percentage increased to 52% because the regional stratosphere was strongly affected by an active fire season.
Design and realization of a discretely loaded resistive vee dipole for ground‐penetrating radars
Authors: Kim Kangwook , Scott Waymond R.
Published: June 2004

A discretely loaded resistive vee dipole (RVD) is designed and realized for use in ground‐penetrating radar (GPR) applications. The RVD is a good antenna for GPR applications because it can radiate a temporally short pulse into a small spot on the ground, and its low radar cross section mostly eliminates the multiple reflections between the surface of the ground and the antenna. The antenna presented in this paper is printed on a circuit board and is discretely loaded with off‐the‐shelf surface‐mount chip resistors. The resulting structure is easy and inexpensive to manufacture and is mechanically stable. The realized antenna is measured in terms of the radiated field and the reflected voltage in the feeding transmission line. The results are compared with those of the antenna with the same resistive loading without substrate. The effects of the transmission line impedance on the performance of the antenna are also presented.
Repeated foreshock sequences in the thrust faulting environment of eastern Taiwan
Authors: Lin Cheng‐Horng
Published: June 2004

Foreshock sequences have repeatedly been observed in the thrust faulting system of the Chengkung area in eastern Taiwan. Examinations of earthquakes since 1992 in this area show all six of the larger earthquakes (ML ≧ 5) had foreshocks at a distance of only a few kilometres within just a few days before the main shocks. The largest earthquake (ML = 6.5) on December 10, 2003 was preceded by two significant foreshocks about four days and 6 minutes respectively prior to the main shock. This earthquake sequence shows the tectonic boundary can most probably be described as a variable‐dip reverse fault. The second largest earthquake occurred on May 28, 1992 (ML = 5.4) was similar with two clear foreshocks. Repeated foreshock sequences in this reverse‐faulting environment are primarily associated with a higher degree of small‐scale heterogeneity in the crust and might very well be considered as potential predictors of large earthquakes in the future.
Effects of the density perturbation in scattering
Authors: Hong Tae‐Kyung , Kennett B. L. N. , Wu Ru‐Shan
Published: June 2004

The influence of density variation on scattering is investigated in terms of attenuation, coda level, and apparent frequency shift. The influence of density variations is to produce more scattered energy than for velocity perturbations alone with a consequently higher coda level. The temporal decay of the coda is reduced, so that high perturbations in density are associated with a long duration of coda. These effects are particularly important for media with small‐scale heterogeneity. Thus inversions for heterogeneity parameters, based on the character of precursors and coda of seismic phases penetrating deep into the Earth, need to take into account the nature of the density variations as well as wave speed variations.
Experimental study of a free and forced swirling jet
Authors: Gallaire F. , Rott S. , Chomaz J.-M.
Published: June 2004

The present study concerns the response of a swirling jet to various azimuthal modes and frequencies forced at the nozzle exit. The different unforced dynamical states are first described as a function of the swirl setting, determined from measured velocity fields in the longitudinal plane using particle image velocimetry. A second experimental technique, based on laser induced fluorescence, is described, which is more suited to the description of the low-amplitude response of the jet to the forcing. It is shown that the receptivity of the jet is very poor when the forcing is set to the naturally prevailing azimuthal mode (m=2) and frequency. In contrast, a strong response is observed for both co-rotating and counter-rotating forced azimuthal modes (m=±2, m=±3) for frequencies about one order of magnitude larger than the frequency prevailing in the absence of forcing. Finally, the present actuator is seen to be ineffective in preventing the appearance of vortex breakdown itself.
Three-dimensional flows in slowly varying planar geometries
Authors: Lauga Eric , Stroock Abraham D. , Stone Howard A.
Published: June 2004

We consider laminar flow in channels constrained geometrically to remain between two parallel planes; this geometry is typical of microchannels obtained with a single step by current microfabrication techniques. For pressure-driven Stokes flow in this geometry and assuming that the channel dimensions change slowly in the streamwise direction, we show that the velocity component perpendicular to the constraint plane cannot be zero unless the channel has both constant curvature and constant cross-sectional width. This result implies that it is, in principle, possible to design “planar mixers,” i.e., passive mixers for channels that are constrained to lie in a flat layer using only streamwise variations of their in-plane dimensions. Numerical results are presented for the case of a channel with sinusoidally varying width.
Energy landscapes and bistability to finite-amplitude disturbances for the capillary bridge
Authors: Bhandar Anand S. , Vogel Michael J. , Steen Paul H.
Published: June 2004

Axial and radial curvatures compete to destabilize the open catenoidal capillary bridge, and once destabilized, to influence its dynamical trajectory. The fates of finite-amplitude disturbances to the stable capillary shapes are mapped out by analysis of potential energy landscapes in combination with bounds on the total energy (kinetic plus potential) assuming viscous dissipation, following techniques from earlier work on the Rayleigh–Taylor problem. Energy landscapes (floor) and energy bounds (ceiling), in combination, form large trapping regions in the parameter space of bridge length l (scaled by contact radius R) and disturbance amplitude ε2. Regions are identified within which disturbances must always return or can never return to the stable base state. Necessarily, sensitive competition between two or more directions in phase-space cannot occur in these regions. We find l=0.542 to be the location of a change in nature of saddle point in the landscape and discuss its implications for the dynamical behavior.
Electrical resistance measurements in a diamond anvil cell to 40 GPa on ytterbium
Authors: Garg Alka B. , Vijayakumar V. , Godwal B. K.
Published: June 2004

An easily assembled setup employing diamond anvil cell, stainless steel gasket and leads, and mylar embedded Al2O3 (alumina) pressure medium for the measurement of electrical resistance of materials under pressure is described. The use of a mylar sheet prevents the alumina layer from sticking to the anvil in the precompacting stage of Al2O3 and also reduces the pressure gradients in the final assembly. The technique is used to reproduce the known transition in Si, Ge, and Fe. The results of measurements of electrical resistance of ytterbium up to 40 GPa are reported. In the hcp phase of ytterbium the electrical resistance increases with pressure. Efforts are made to explain the variation of resistance with pressure from known band structure calculations.
Detector system with high time resolution for the continuous measurement of spectra in the vacuum ultraviolet wavelength range
Authors: Biel W. , Bertschinger G. ,   the TEXTOR Team
Published: June 2004

A new detector system with high time resolution (1 ms) has been developed and applied for the continuous measurement of spectra in the vacuum ultraviolet (VUV) and extreme ultraviolet (EUV) wavelength region at the fusion plasma experiment Torus Experiment for Technology-Oriented Research (TEXTOR). The system consists of an open multichannel-plate (MCP) detector with subsequent first generation (Gen I) light amplifier and a camera head which is based on a linear photodiode array with 1024 elements (pixels). The camera head provides the output signals of the individual pixels sequentially as an analog voltage with a full spectra rate of 1000 per second, which are measured using a PC-based data acquisition system. Three vacuum spectrometers operating in the VUV/EUV region (10–130 nm) have been equipped with the new system and a successful campaign of measurements from about 4000 discharges at TEXTOR has been performed. Spectra are recorded with a usable linear dynamic range of 10 bit and a wavelength resolution corresponding to a width of 3–4 pixels.
Fingering phenomena created by a soluble surfactant deposition on a thin liquid film
Authors: Warner M. R. E. , Craster R. V. , Matar O. K.
Published: June 2004

A striking fingering instability accompanies surfactant droplet deposition upon thin films. The fingers apparently emerge from the droplet and are preceded by a circular rim of thickened fluid. In this work, we present a theory, based on the lubrication approximation, capable of explaining the physical mechanism responsible for these phenomena and the trends observed experimentally. The model comprises evolution equations for the film thickness and surfactant interfacial and bulk concentrations, which are parametrized by appropriately defined solubility and sorption kinetics parameters, and surface and bulk Peclet numbers; closure is achieved via use of a nonlinear equation of state. The results of our transient growth analysis and two-dimensional numerical simulations illustrate the delicate interplay, which exists between surfactant solubility and the nonlinearity in the equation of state. In particular, we show that solubility acts to destabilize the spreading process for a given value of the nonlinearity except for very highly soluble surfactants. In this case, the magnitude of the Marangoni stresses available to drive spreading and instability diminishes leading to flow stability.
Waveguiding in air by total external reflection from ultralow index metamaterials
Authors: Schwartz Brian T. , Piestun Rafael
Published: June 2004

Metamaterials composed of metal-dielectric nanostructures can be engineered to have the real part of the effective refractive index less than unity at optical wavelengths. These materials show intriguing optical properties including total external reflection. We utilize this effect to design and analyze slab waveguide structures that guide visible light in an air core.
Photofragment image analysis via pattern recognition
Authors: Manzhos Sergei , Loock Hans-Peter
Published: June 2004

An algorithm is presented that solves two problems associated with the analysis of velocity map images, which are used, for example, in the study of photofragmentation or photoionization processes. The first part of the algorithm identifies the center, the ring radii, and distortions of circularity without any a priori knowledge about the image. Derived from the Hough transform, it is highly robust with respect to uneven distributions of intensity, background signals, and realistic distortions of circularity. In the second independent part of the algorithm the image parameters are calculated using an analytical description of the image. Here the velocity profile, branching ratios, and spatial anisotropy parameters are obtained directly from the raw image for any form of the velocity broadening function, i.e., without the necessity for “inversion” of the image.
On the initialization of Rayleigh–Taylor simulations
Authors: Ramaprabhu P. , Andrews M. J.
Published: June 2004

We demonstrate that, when initialized with experimental data, numerical simulations of Rayleigh–Taylor mixing show reasonable agreement with experimental measurements of the self-similar growth rate α. The experimental data include high-resolution velocity and density measurements from a closed water channel facility. For the simulations, a monotone integrated large eddy simulations technique was used that employed a finite-volume, Eulerian equation solver with van Leer flux limiters. Calculations were initialized with both density and velocity fluctuations. A comparison of the late-time, self-similar growth constant with the experiments showed simulations initialized with velocity perturbations gave better agreement with experiments.
Magnetotransport properties of Co–Fe∕Al–N∕Co–Fe tunnel junctions with large tunnel magnetoresistance ratio
Authors: Yoon Tae Sick , Kim Chong Oh , Shoyama Toshihiro , Tsunoda Masakiyo , Takahashi Migaku
Published: June 2004

The magnetotransport properties of tunnel junctions with the structure of Ta 5nm∕Cu20nm∕Ta 5nm∕Ni76Fe242nm∕Cu 5nm∕Mn75Ir2510nm∕Co71Fe29 4nm∕Al–N∕Co71Fe29 4nm∕Ni76Fe2420nm∕Ta5nm were investigated. When the Al thickness, nitridation time, and annealing temperature were 1nm(0.8nm), 50s(35s), and 280°C(300°C), tunnel magnetoresistance (TMR) ratio and resistance-area product were 49%(34%) and 3×104Ωμm2(1.5×104Ωμm2), respectively. In order to clarify the annealing temperature dependence of TMR ratio, the local transport properties were studied using conducting atomic force microscope for Ta5nm∕Cu20nm∕Ta5nm∕Ni76Fe242nm∕Cu5nm∕Mn75Ir25 10nm∕Co71Fe29 4nm∕Al(0.8nm)–N junction fabricated with the nitridation time of 35s and Ar+N2 plasma as a function of annealing temperature. The large TMR at 300°C, where the TMR ratio of the corresponding magnetic tunnel junction had the maximum value of 34%, could be well elucidated by the enhancement of the average barrier height ϕave, and the reduction of its fluctuation. After annealing at 340°C, the leakage current was observed and the TMR ratio decreased.
Single-shot autocorrelator based on a Babinet compensator
Authors: Wasylczyk Piotr , Wasilewski Wojciech , Radzewicz Czesław
Published: June 2004

A compact, single-shot, second-harmonic autocorrelator for ultrashort laser pulse measurements is presented. The autocorrelator uses a Babinet compensator to split the pulse to be measured into two replicas with a relative delay between them varying across the beam. It consists of a few optical elements only, requires no sensitive alignment, and offers a robust diagnostics tool for low repetition rate femtosecond laser amplifiers.
Experimental evidence of omnidirectional elastic bandgap in finite one-dimensional phononic systems
Authors: Manzanares-Martínez Betsabe , Sánchez-Dehesa José , Håkansson Andreas , Cervera Francisco , Ramos-Mendieta Felipe
Published: June 2004

We present an experimental demonstration of the occurence of omnidirectional reflection in a finite multilayer of two elastic materials. This property is demonstrated in three different samples consisting of a few periods of Pb∕Epoxy. The effect is fullfiled thanks to the large mismatch between the elastic parameters of the two materials in the multilayer. The thicknesses of the layers were chosen in order to have the omnidirectional gap at a few hundreds of kHz. The theoretical treatment of the phononic band structure of the corresponding superlattice as well as the transmission properties through the finite structures are in good agreement with the transmission measurements.
Impurity-induced magnetic units embedded in ferromagnetic surfaces
Authors: Prandolini M. J. , Manzhur Y. , Weber A. , Potzger K. , Bertschat H. H. , Ueno H. , Miyoshi H. , Dietrich M.
Published: June 2004

Induced magnetic properties at isolated nonmagnetic atoms (Cd) attached to ferromagnetic Ni surfaces are found to be independent of the local symmetry and dependent on the number of nearest Ni neighbors. This dominance of coordination-number dependence as opposed to local symmetry could be studied on differently oriented surfaces at constant coordination numbers using perturbed angular correlation spectroscopy. Mediated by the localized sd-electron hybridization, the impurities form zero-dimensional magnetic units with their nearest Ni neighbors. We discuss this finding as basic research toward future applications with self-organizing patterned structures.
Frequency band gap for Rayleigh waves on coated substrates
Authors: Declercq Nico F. , Degrieck Joris , Leroy Oswald
Published: June 2004

The Rayleigh wave velocity for a coated substrate must have a value in between the ones for the substrate material and the coating material. Nevertheless, Adler and McCathern [J. Appl. Phys. 49, 2576 (1978)] have performed measurements, based on the Schoch effect, on a stainless steel substrate covered with an aluminum oxide coating that contradict this phenomenon. The current letter describes the frequency band gap effect for Rayleigh waves on coated substrates and explains how this phenomenon is related to the cited measurements. The existence of such a gap can be very important for the development of frequency filters.
Electromechanical and ferroelectric properties of (Bi1∕2Na1∕2)TiO3–(Bi1∕2K1∕2)TiO3–BaTiO3 lead-free piezoelectric ceramics
Authors: Wang X. X. , Tang X. G. , Chan H. L. W.
Published: June 2004

Lead-free piezoelectric ceramics (0.95−x)(Bi1∕2Na1∕2)TiO3–x(Bi1∕2K1∕2)TiO3–0.05BaTiO3 (abbreviated as BNT–BKT–BT100x, with x ranged from 0 to 20mol%) have been studied. Effects of amount of BKT on the electrical properties and crystal structure were examined. BNT–BKT–BT5 ceramics give good performances with piezoelectric constant d33=148pC∕N, electromechanical coupling factor kp=34%, kt=49.2%, free permittivity ε33T∕ε0=700, and dissipation factor tanδ=2% at 1kHz. Accordingly, the sample shows larger remanent polarization and lower coercive field than 0.95BNT–0.05BT ceramics. X-ray diffraction analysis shows that incorporated BKT diffuses into the BNT–BT lattice to form a solid solution during sintering, but changes the crystal structure from rhombohedral to tetragonal symmetry at higher BKT amounts.
Growth mechanism difference of sputtered HfO2 on Ge and on Si
Authors: Kita Koji , Kyuno Kentaro , Toriumi Akira
Published: June 2004

HfO 2 films were deposited by the reactive sputtering on Ge and Si substrates simultaneously, and we found both the interface layer and the HfO2 film were thinner on Ge substrate than those on Si substrate. A metallic Hf layer has a crucial role for the thickness differences of both interface layer and HfO2 film, since those thickness differences were observed only when an ultrathin metallic Hf layer was predeposited before the reactive sputtering process. The role of metallic Hf in these phenomena is understandable by assuming the formation of a volatile Hf–Ge–O ternary compound at the early stage of the film growth. This result shows that the HfO2∕Ge system has an advantage over the HfO2∕Si system from the viewpoint of further reduction of the gate oxide film thickness.
Probing the dispersive and spatial properties of photonic crystal waveguides via highly efficient coupling from fiber tapers
Authors: Barclay P. E. , Srinivasan K. , Borselli M. , Painter O.
Published: June 2004

The demonstration of an optical fiber based probe for efficiently exciting the waveguide modes of high-index contrast planar photonic crystal (PC) slabs is presented. Fiber taper waveguides formed from standard silica single-mode optical fibers are used to evanescently couple light into the guided modes of a patterned silicon membrane. A coupling efficiency of ∼95% is obtained between the fiber taper and a PC waveguide mode suitably designed for integration with a previously studied ultrasmall mode volume high-QPC resonant cavity [Srinivasan et al., Appl. Phys. Lett. 83, 1915 (2003)]. The micron-scale lateral extent and dispersion of the fiber taper is used as a near-field spatial and spectral probe to study the profile and dispersion of PC waveguide modes.
Oriented semiconducting polymer nanostructures as on-demand room-temperature single-photon sources
Authors: Lee Tae-Hee , Kumar Pradeep , Mehta Adosh , Xu Kewei , Dickson Robert M. , Barnes Michael D.
Published: June 2004

We show that oriented nanostructures from single molecules of a conducting polymer act as highly robust room-temperature single-photon sources. Individual z-oriented polymer nanostructures show high-contrast photon antibunching with a modulation depth exceeding 90%. These results suggest the feasibility of a “push-button” technology for polymer-based single-photon sources in photonic-based quantum information processing applications.
Dominant carrier recombination mechanisms in GaInNAs∕GaAs quantum well light-emitting diodes
Authors: Ulloa J. M. , Hierro A. , Miguel-Sánchez J. , Guzmán A. , Tournié E. , Sánchez-Rojas J. L. , Calleja E.
Published: June 2004

The electroluminescence of GaInNAs∕GaAs quantum well light-emitting diodes is analyzed as a function of temperature and injection current. The relative influence of nonradiative carrier recombination, recombination from localized states, and conduction-band to valence-band recombination is discussed. The localized states are found to dominate the emission and the external quantum efficiency only at low temperatures and currents. When temperature and∕or injection level are increased, band-to-band transitions become the main recombination mechanism. Nonradiative recombination is strongly thermally activated, and becomes the dominant process above 75K. As a result of postgrowth rapid thermal annealing, the device luminescence efficiency increases by over one order of magnitude due to a decrease in the density of nonradiative recombination centers.
Co
2
Mn
Si
Heusler alloy as magnetic electrodes in magnetic tunnel junctions
Authors: Kämmerer S. , Thomas A. , Hütten A. , Reiss G.
Published: June 2004

As a consequence of the growing theoretical predictions of 100% spin-polarized half- and full-Heusler compounds over the past six years, Heusler alloys are among the most promising materials class for future magnetoelectronic and spintronic applications. We have integrated Co2MnSi, as a representative of the full-Heusler compound family, as one magnetic electrode into magnetic tunnel junctions. The preparation strategy has been chosen so as to sputter Co2MnSi at room temperature onto a V-buffer layer, which assists in (110) texture formation, and to deposit the Al-barrier layer directly thereafter. After plasma oxidizing the Al-barrier layer, subsequent annealing leads (1) to the texture formation and (2) to the appropriate atomic ordering within the Co2MnSi, and (3) homogenizes the AlOx barrier. It is shown that the magnetic switching of the ferromagnetic electrodes is well controlled from room temperature down to 10K. The resulting tunnel magnetoresistance-effect amplitude of the Co2MnSi containing magnetic tunnel junctions has been determined as a function of temperature and the spin polarization of the Co2MnSi Heusler compound has been estimated to be 61% at 10K. Thus, the spin polarization of the Co2MnSi layer at 10K exceeds that of conventional transition metals.
Optical nonlinearity enhancement of graded metallic films
Authors: Huang J. P. , Yu K. W.
Published: June 2004

The effective linear and third-order nonlinear susceptibility of graded metallic films with weak nonlinearity have been investigated. Due to the simple geometry, we were able to derive exactly the local field inside the graded structures having a Drude dielectric gradation profile. We calculated the effective linear dielectric constant and third-order nonlinear susceptibility. We investigated the surface plasmon resonant effect on the optical absorption, the optical nonlinearity enhancement, and the figure of merit of graded metallic films. It is found that the presence of gradation in metallic films yields a broad resonant plasmon band in the optical region, resulting in a large enhancement of the optical nonlinearity, and hence a large figure of merit. We suggest experiments be done to check our theoretical predictions, because graded metallic films can be fabricated more easily than graded particles.
Self-assembled rigid conjugated polymer nanojunction and its nonlinear current–voltage characteristics at room temperature
Authors: Hu Wenping , Nakashima Hiroshi , Furukawa Kazuaki , Kashimura Yoshiaki , Ajito Katsuhiro , Torimitsu Keiichi
Published: June 2004

A gold/polymer/gold nanojunction was fabricated by the self-assembly of a rigid polymer, namely poly(p-phenyleneethynylene)s with thioacetyl groups, between gold nanogap electrodes. The self-assembly depends on: (i) the ideal rigidity of the polymer molecules and (ii) the strong affinity of the thioacetyl/thiol end groups of the polymer for the Au surface. The current–voltage (I–V) characteristics of the conjugated polymer nanojunction exhibited stepwise features (some steps appeared as peaks) at room temperature. The I–V can be explained as electron tunneling through the nanojunction.