bluuebunny/crossref_metadata_2025 huggingface dataset:
Levels of a scale‐free tree
Authors: Katona Zsolt
Published: December 2005

Consider the random graph model of Barabási and Albert, where we add a new vertex in every step and connect it to some old vertices with probabilities proportional to their degrees. If we connect it to only one of the old vertices the graph will be a tree. These graphs have been shown to have power law degree distributions, the same as observed in some large real‐world networks. We show that the degree distribution is the same on every sufficiently high level of the tree. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006
Average case analysis of the Boyer‐Moore algorithm
Authors: Tsai Tsung‐Hsi
Published: December 2005

Limit theorems (including a Berry‐Esseen bound) are derived for the number of comparisons taken by the Boyer‐Moore algorithm for finding the occurrences of a given pattern in a random text. Previously, only special variants of this algorithm have been analyzed. We also propose a means of computing the limiting constants for the mean and the variance. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006.
On ε‐biased generators in NC0
Authors: Mossel Elchanan , Shpilka Amir , Trevisan Luca
Published: December 2005

Cryan and Miltersen (Proceedings of the 26th Mathematical Foundations of Computer Science, 2001, pp. 272–284) recently considered the question of whether there can be a pseudorandom generator in NC0, that is, a pseudorandom generator that mapsn‐bit strings tom‐bit strings such that every bit of the output depends on a constant numberkof bits of the seed.

They show that fork= 3, ifm≥ 4n+ 1, there is a distinguisher; in fact, they show that in this case it is possible to break the generator with alinear test, that is, there is a subset of bits of the output whose XOR has a noticeable bias.

They leave the question open fork≥ 4. In fact, they ask whether every NC0generator can be broken by a statistical test that simply XORs some bits of the input. Equivalently, is it the case that no NC0generator can sample an ε‐biased space with negligible ε?

We give a generator fork= 5 that mapsnbits intocnbits, so that every bit of the output depends on 5 bits of the seed, and the XOR of every subset of the bits of the output has bias 2. For large values ofk, we construct generators that mapnbits to$n^{\Omega(\sqrt{k})}$bits such that every XOR of outputs has bias$2^{-{n^{{1 \over 2\sqrt k}}}}$.

We also present a polynomial‐time distinguisher fork= 4,m≥ 24nhaving constant distinguishing probability. For large values ofkwe show that a linear distinguisher with a constant distinguishing probability exists oncem≥ Ω(2kn⌈k/2⌉).

Finally, we consider a variant of the problem where each of the output bits is a degreekpolynomial in the inputs. We show there exists a degreek= 2 pseudorandom generator for which the XOR of every subset of the outputs has bias 2−Ω(n)and which mapsnbits to Ω(n2) bits. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006
Law of large numbers for increasing subsequences of random permutations
Authors: Pinsky Ross G.
Published: December 2005

Let the random variable Zn,k denote the number of increasing subsequences of length k in a random permutation from Sn, the symmetric group of permutations of {1,…,n}. We show that Var(Z) = o((EZ)2) as n → ∞ if and only if
$k_n=o(n^{{2\over 5}})$. In particular then, the weak law of large numbers holds for Z if $k_n=o(n^{{2\over 5}})$; that is,

We also show the following approximation result for the uniform measure Un on Sn. Define the probability measure μ on Sn by

where U denotes the uniform measure on the subset of permutations that contain the increasing subsequence {x1,x2,…,x}. Then the weak law of large numbers holds for Z if and only if

where ∣∣˙∣∣ denotes the total variation norm. In particular then, (*) holds if $k_n=o(n^{{2\over 5}})$.

In order to evaluate the asymptotic behavior of the second moment, we need to analyze occupation times of certain conditioned two‐dimensional random walks. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006
Coloring complete bipartite graphs from random lists
Authors: Krivelevich Michael , Nachmias Asaf
Published: December 2005

Let Kn,n be the complete bipartite graph with n vertices in each side. For each vertex draw uniformly at random a list of size k from a base set S of size s = s(n). In this paper we estimate the asymptotic probability of the existence of a proper coloring from the random lists for all fixed values of k and growing n. We show that this property exhibits a sharp threshold for k ≥ 2 and the location of the threshold is precisely s(n) = 2n for k = 2 and approximately
$s(n)={{n}\over{2^{k-1}\ln 2}}$
for k ≥ 3. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006
Covering minimum spanning trees of random subgraphs
Authors: Goemans Michel X. , Vondrák Jan
Published: December 2005

We consider the problem of finding a sparse set of edges containing the minimum spanning tree (MST) of a random subgraph of G with high probability. The two random models that we consider are subgraphs induced by a random subset of vertices, each vertex included independently with probability p, and subgraphs generated as a random subset of edges, each edge with probability p.

Let n denote the number of vertices, choose p ∈ (0, 1) possibly depending on n, and let b = 1/(1 − p). We show that in both random models, for any weighted graph G, there is a set of edges Q of cardinality O(n logbn) that contains the minimum spanning tree of a random subgraph of G with high probability. This result is asymptotically optimal. As a consequence, we also give a bound of O(kn) on the size of the union of all minimum spanning trees of G with some k vertices (or edges) removed. More generally, we show a bound of O(n logbn) on the size of a covering set in a matroid of rank n, which contains the minimum‐weight basis of a random subset with high probability. Also, we give a randomized algorithm that calls an MST subroutine only a polylogarithmic number of times and finds the covering set with high probability. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006
A spectral heuristic for bisecting random graphs
Authors: Coja‐Oghlan Amin
Published: December 2005

The minimum bisection problem is to partition the vertices of a graph into two classes of equal size so as to minimize the number of crossing edges. Computing a minimum bisection is NP‐hard in the worst case. In this paper we study a spectral heuristic for bisecting random graphs Gn(p,p′) with a planted bisection obtained as follows: partition n vertices into two classes of equal size randomly, and then insert edges inside the two classes with probability p′ and edges crossing the partition with probability p independently. If $n(p'-p)\geq c_0\sqrt{np'\ln(np')}$, where c0 is a suitable constant, then with probability 1 − o(1) the heuristic finds a minimum bisection of Gn(p,p′) along with a certificate of optimality. Furthermore, we show that the structure of the set of all minimum bisections of Gn(p,p′) undergoes a phase transition as $n(p'-p)=\Theta(\sqrt{np'\ln n})$. The spectral heuristic solves instances in the subcritical, the critical, and the supercritical phases of the phase transition optimally with probability 1 − o(1). These results extend previous work of Boppana Proc. 28th FOCS (1987) 280–285. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006
Representations of science within children's trade books
Authors: Ford Danielle J.
Published: December 2005

The use of trade books in science instruction, particularly in the elementary and middle school grades, invites scrutiny into the ways in which trade books represent science and its practitioners to learners. Forty‐four trade books were examined for their explicit and implicit representations of science. The majority of the sample was comprised of informational texts, followed by experiment books and artistic books. Scientific knowledge was generally represented as facts, with limited connections to the producers of those facts. Scientists and their practice were represented as experiment or observation, in descriptions that blurred the distinctions between levels of participation in science, and emphasized empirical data collection over analysis or theory development. Artistic books focused on nature encouraged an aesthetic approach to nature, primarily through creative observation. These books are not likely to convey a sophisticated image of the nature of science to young children without contextualization by teachers and other knowledgeable adults. However, they have potential as tools within inquiry contexts, if used in a manner authentic to goals for scientific literacy. © 2005 Wiley Periodicals, Inc. J Res Sci Teach 43: 214–235, 2006
Exploring alternative conceptions from Newtonian dynamics and simple DC circuits: Links between item difficulty and item confidence
Authors: Planinic Maja , Boone William J. , Krsnik Rudolf , Beilfuss Meredith L.
Published: December 2005

Croatian 1st‐year and 3rd‐year high‐school students (N = 170) completed a conceptual physics test. Students were evaluated with regard to two physics topics: Newtonian dynamics and simple DC circuits. Students answered test items and also indicated their confidence in each answer. Rasch analysis facilitated the calculation of three linear measures: (a) an item‐difficulty measure based upon all responses, (b) an item‐confidence measure based upon correct student answers, and (c) an item‐confidence measure based upon incorrect student answers. Comparisons were made with regard to item difficulty and item confidence. The results suggest that Newtonian dynamics is a topic with stronger students' alternative conceptions than the topic of DC circuits, which is characterized by much lower students' confidence on both correct and incorrect answers. A systematic and significant difference between mean student confidence on Newtonian dynamics and DC circuits items was found in both student groups. Findings suggest some steps for physics instruction in Croatia as well as areas of further research for those in science education interested in additional techniques of exploring alternative conceptions. © 2005 Wiley Periodicals, Inc. J Res Sci Teach 43: 150–171, 2006
New Chalcogenidoarsenates with Transition Metal Complex Cations: [M(en)3]2As2S5 (M = Mn, Ni) and [Mn(en)3]2As2Se5
Authors: Jia Ding‐Xian , Zhao Qian‐Xin , Dai Jie , Zhang Yong , Zhu Qin‐Yu
Published: December 2005

New chalcogenidoarsenate compounds [M(en)3]2As2S5 (en = ethylenediamine, M = Mn (1), Ni (2)), and [Mn(en)3]2As2Se5 (3) were synthesized by the reaction of transition metal chloride, arsenous oxide, and elemental sulfur (or selenium) in en at 140 °C. The compounds are consist of isolated [As2E5]4− (E = S, Se) anions and transition metal [M(en)3]2+ cations. The dimeric [As2E5]4− anion, which is constructed by two corner‐sharing AsE3 trigonal pyramids, was first isolated and co‐crystallized with transition metal complex cations as counterions. The compound 1 crystallizes in P212121 space group, while both 2 and 3 are in Pbca space group. The thermal behaviors of the compounds are related to their crystal structures. On heating, compound 1 decomposes in two steps, while compounds 2 and 3 decompose in one step. The decomposition products of the compounds are studied by XRD.
Halbantiperowskite II: zur Kristallstruktur des Pd3Bi2S2
Authors: Weihrich Richard , Anusca Irina
Published: December 2005

Halfantiperovskites II: on the Crystal Structure of Pd3Bi2S2

The crystallographic structure of Pd3Bi2S2 was determined from x‐ray diffraction data and compared to parkerite (Ni3Bi2S2), shandite (Ni3Pb2S2), and a high pressure form of laflammeite (Pd3Pb2S2). For Pd3Bi2S2 the structure type of corderoite, Hg3S2Cl2 (I213) was found that represents a cubic variant (a = 8,3097(9) Å) of the parkerite structure. It turns out to be a structural antitype of the low temperature cubic modification of K2Sn2O3, analogously to the previously investigated type‐antitype relation of shandit to high‐temperature K2Sn2O3. The crystal structures are derived from perovskites ABO3 and antiperovskites M3AX with only half of the O‐ and M‐sites being occupied. The M = Ni, Pd site ordering in shandite and parkerite type compounds is discussed in terms of ordered half antiperovskite (HAP) structures M3/2AS (A = Bi, Pb). The electronic band structure of Pd3Bi2S2 is calculated within the framework of density functional theory. The compound is found to behave metallic while K2Sn2O3 and corderoite are semiconductors. The bonding is analysed in terms of covalently bond [Pd3S2]δ− networks as proposed for [Sn2O3]2− and [Hg3S2]2+.
A New Preparative Approach to HgPbP14 Structure Type Materials: Crystal Structure of Cu0.73(1)Sn1.27(1)P14 and Characterization of M1−xSn1+xP14 (M = Cu, Ag) and AgSbP14
Authors: Lange Stefan , Sebastian C. Peter , Nilges Tom
Published: December 2005

A new preparative approach, using main group iodides as mineralization agents, was developed to prepare bulk quantities of HgPbP14 [(M1)(M2)P14] type polyphosphides containing group 11 cations on the M1 and main group elements Sn or formerly unseen Sb on the M2 position. The known (M1)2+:(M2)2+ combination of cations is extended with the combination (M1)1+:(M2)3+ in AgSbP14. A single crystal structure determination was performed for Cu1−xSn1+xP14. Cu0.73(1)Sn1.27(1)P14 crystallizes orthorhombically, space group Pnma (No. 62) with lattice constants a = 12.513(2) Å, b = 9.800(1) Å, c = 10.445(1) Å, V = 1280.8(3) Å3 and Z = 4. Small differences in the cell parameters between the single crystal and powder diffraction experiments of CuSnP14 are probably due to a small homogeneity range. Tetravalent tin postulated beside divalent tin for isostructural Au0.64Sn1.36P14 could not be detected by 119Sn‐Mössbauer spectroscopic experiments for the copper tin polyphosphide.

An ionic description like [(M1+)1−x(M24+)x]2+ [(M22+)(P0)10(P1−)4]2− with x = 0.33 according to a Zintl‐Klemm concept has to be substituted by a more covalent description of [(M1+)1−x(M22+)x](1+x)+[(M22+)(P14)](1+x)− for the copper tin polyphosphide.
Synthese und Struktur chiraler Heterometallatetrahedrane des Typs [Re2(M1PPh3)(M2PPh3)(μ‐PCy2)(CO)7C≡CPh] (M1 = Ag, Au; M2 = Cu, Ag, Au)
Authors: Seewald Oliver , Flörke Ulrich , Egold Hans , Haupt Hans‐Jürgen , Schwefer Meinhard
Published: December 2005

Syntheses and Structure of Chiral Metallatetrahedron Complexes of the Type [Re2(M1PPh3)(M2PPh3)(μ‐PCy2)(CO)7C≡CPh] (M1 = Ag, Au; M2 = Cu, Ag, Au)

From the reaction of Li[Re2(μ‐H)(μ‐PCy2)(CO)7(C(Ph)O)] (1) with Ph3AuC≡CPh both benzaldehyde and the trinuclear complex Li[Re2(AuPPh3)(μ‐PCy2)(CO)7C≡CPh] (2a) were obtained in high yield. The complex anion was isolated as its PPh4‐salt 2b. The latter reacts with coinage metal complexes PPh3M2Cl [M2 = Cu, Ag, Au] to give chiral heterometallatetrahedranes of the general formula [Re2(AuPPh3)(M2PPh3)(μ‐PCy2)(CO)7C≡CPh] (M2 = Cu 3a, Ag 3b, Au 3c). The corresponding complex [Re2(AgPPh3)2(μ‐PCy2)(CO)7C≡CPh] (3d) is obtained from the reaction of [Re2(AgPPh3)2(μ‐PCy2)(CO)7Cl] (4) with LiC≡CPh. 3d undergoes a metathesis reaction in the presence of PPh3CuCl giving [Re2(AgPPh3)(CuPPh3)(μ‐PCy2)(CO)7C≡CPh] (3e) and PPh3AgCl. Analogous metathesis reactions are observed when 3c is reacted with PPh3AgCl or PPh3CuCl giving 3a or 3b, respectively. The reaction of 1 with PPh3AuCl gives benzaldehyde and Li[Re2(AuPPh3)(μ‐PCy2)(CO)7Cl] (5a) which upon reaction with PhLi forms the trinuclear complex Li[Re2(AuPPh3)(μ‐PCy2)(CO)7Ph] (6a). Again this complex was isolated as its PPh4‐salt 6b. In contrast to 2b, 6b reacts with one equivalent of Ph3PAuCl by transmetalation to give Ph3PAuPh and PPh4[Re2(AuPPh3)(μ‐PCy2)(CO)7Cl] (5b). The X‐ray structures of the compounds 3a, 3b, 3e and 4 are reported.
Cs3Se22, a Selenium‐rich Caesium Polyselenide containing Se8 Crowns and $^{3}_{\infty}\rm [Se_{6}^{3-}]$ Anions with Radical Character
Authors: Kromm Anna , Sheldrick William S.
Published: December 2005

Cs3Se22 can be prepared together with the known compounds Cs2Sn2Se6 and Cs4Sn2Se6 by reacting Cs2CO3 and Sn in a CH3OH/en solution at 120 °C. The presence of CuCl and the macrocyclic ligand 1,10‐dithia‐18‐crown‐6 are essential for product formation. The caesium polyselenide consists of anionic nets $^{3}_{\infty}\rm [Se_{6}^{3-}]$ that are separated by two layers of discrete Se8 rings. Within the polymeric anions pairs of Se3·− radical anions and Se32− anions are linked through secondary interactions.
Synthesis and Crystal Structure of Ammonium Cyanimide NH4HCN2
Authors: Roßmeier Thomas , Korber Nikolaus
Published: December 2005

The compound NH4HCN2 (1) was prepared by the reaction of H2CN2 with liquid ammonia. The ammonium salt 1 was characterized by a low temperature single‐crystal X‐ray structure analysis. The anionic part of the structure consists of HCN2− anions, which are connected via N–H···N bonds (H···N distance: 2.47Å, DHA: 165°). The N–H···N hydrogen bonds of the ammonium ion to the anions range from 2.00 to 2.14Å (DHA = Donor···Acceptor angles: 165–176°), all N–H···N interactions together give rise to a three‐dimensional network. 1 decomposes quantitatively to dicyandiamide at room temperature.
Syntheses of Trifluoromethanethiolato Platinum(II) Complexes – Crystal Structures of cis‐Pt(SCF3)2(PPh3)2 and trans‐Pt(SCF3)Cl(PPh3)2
Authors: Kirij Natalya V. , Tyrra Wieland , Naumann Dieter , Pantenburg Ingo , Yagupolskii Yurii L.
Published: December 2005

Ligand exchange reactions of cis‐PtCl2(PPh3)2 and [NMe4]SCF3 in different ratios were studied. Depending on the stoichiometry reactions proceeded with formation of products expected for the chosen ratio, i. e. cis‐Pt(SCF3)Cl(PPh3)2, cis‐Pt(SCF3)2(PPh3)2, and [NMe4][Pt(SCF3)3(PPh3)]. Starting from cis‐PtCl2(MeCN)2 and [NMe4]SCF3 and adding PPh3 after substitution, product mixtures were dominated by the corresponding trans‐isomers. Results of the single crystal structure analyses of cis‐Pt(SCF3)2(PPh3)2 and trans‐Pt(SCF3)Cl(PPh3)2 are discussed.
Morpholin als ambidenter Ligand
Authors: Iravani Effat , Neumüller Bernhard
Published: December 2005

Morpholine as Ambident Ligand

The reaction of MeInCl2 with Li‐morpholinate [Li(Morph)] at 20 °C in THF gave after work‐up and recrystallization from diglyme the salt [Li(Diglyme){In3Me2Cl4(Morph)4}]·Diglyme (1). The treatment of the reaction mixture of MesInCl2/Li(Morph) with wet THF yield as only isolated compound the coordination polymer [Li6Cl6(HMorph)3] (2). Under similar conditions the reaction of InCl3 with Li(Morph) led after work‐up in wet THF to [Li(Diglyme)2][InCl4(HMorph)2] (3). 1 – 3 were characterized by NMR and IR spectroscopy as well as by X‐ray analysis. According to this, 1 contains the trinuclear anion [In3Me2Cl4(Morph)4]− in which one of the morpholinate ligands is coordinated via N atom to the In3+ ions, while the O atom belongs to the coordination sphere of the Li+ ion. In 2, LiCl forms a hexagonal heteroprismn, in which the morpholine molecules are responsible for a 3d network via coordination of both Lewis‐basic heteroatoms. 3 contains trans‐[InCl4(Hmorph)2]− ions, connected by hydrogen bonding along [011].
Differing Coordination Modes of (O‐Alkyl)‐p‐Ethoxyphenyldithiophosphonato Ligands in Copper(I), Silver(I) and Gold(I) Triphenylphosphine Complexes
Authors: Haiduc Ionel , Mezei Gellert , Micu‐Semeniuc Rodica , Edelmann Frank T. , Fischer Axel
Published: December 2005

The three (O‐methyl)‐p‐ethoxyphenyldithiophosphonato triphenylphosphine complexes of copper, silver and gold, [(Ph3P)nM{S2P(OMe)C6H4OEt‐p}] (M = Cu, n = 2; M = Ag, Au, n = 1) investigated structurally by X‐ray diffraction exhibit remarkable structural differences. The copper compound is a four‐coordinate chelate monomer with Cu–S 2.4417(6) and 2.5048(6) Å; P–Cu–S 104.24(2)–114.01(2)°; Cu–S–P 82.49(3)° and 80.85(2)°. The silver compound is a cyclic dimer with bridging dithiophosphonato ligands and three‐coordinate silver atoms [Ag–S 2.5371(5) and 2.6867(5) Å; P–Ag–S 122.88(2)° and 122.17(2)°; Ag–S–P 89.32(2)° and 103.56(2)°]. The gold compound is monomeric with linear dicoordinate gold [Au–S 2.3218(6) Å; P–Au–S 177.72(2)°, Au–S–P 100.97(3)°].
Hydrothermal Synthesis and Structures of Two New Molybdenum Phosphate Compounds based on Keggin Cluster Units
Authors: Zhang Quan‐Zheng , Lu Can‐Zhong
Published: December 2005

Two new molybdenum phosphate complexes, [Cu2(phen)4(μ‐Cl)][PMo12O40]·H2O (phen = 1,10‐phenanthroline) (1) and (Hbpy)[CuI(bpy)]2[PMoV2MoVI10O39] (bpy = 4,4′‐bipyridine) (2), have been prepared under mild hydrothermal conditions and structurally characterized by single‐crystal X‐ray diffraction. Compounds 1 and 2 crystallize in triclinic system, space group ${\rm P}{\bar 1}$, with a = 12.5458(7) Å, b = 13.4486(8) Å, c = 21.2406(12) Å, α = 99.7020(10)°, β = 94.2320(10)°, γ = 95.0890(10)°, V = 3504.2(3) Å3 and Z = 2 for 1, and a = 10.7871(6) Å, b = 10.9016(6) Å, c = 12.7897(7) Å, α = 96.8500(10)°, β = 110.0850(10)°, γ = 103.5800(10)°, V = 1339.74(13) Å3 and Z = 1 for 2. Compound 1 contains a [Cu2(phen)4(μ‐Cl)]3+ cation in which two similar [Cu(phen)2] units are bridged by one chlorine atom. Compound 2 contains one‐dimensional straight chain of Keggin polyoxoanions [PMoV2MoVI10O39]n3− and two linear cationic chains of [CuI(bpy)]nn+. The molecular packing shows a two‐dimensional network, which is formed by the cross of the linear Keggin anions and Cu‐bpy cations.
Synthesen und Strukturen der Titan(III)‐siloxane [Ti(OSiPh3)3(thf)2] und [Ti(OSiPh3)3(py)2]
Authors: Veith Michael , Voigt Thorsten , Huch Volker
Published: December 2005

Syntheses and Structures of the Titanium(III) Siloxanes [Ti(OSiPh3)3(thf)2] and [Ti(OSiPh3)3(py)2]

The new titaniumtrioxysilanes [Ti(OSiPh3)3(thf)2] (1) and [Ti(OSiPh3)3(py)2] (2) have been obtained from the reaction of titaniumtrichloride with LiOSiPh3 in the presence of the corresponding bases tetrahydrofurane (thf) and pyridine (py). From the crystal structures of both compounds it is evident that the titanium atoms are in the centres of trigonal‐bipyramidal coordination figures, with the donor atoms in axial positions. The compounds 1 and 2 have slightly different structures (mean values: 1: Ti‐O(Si) 1.897(9), Ti‐O(C) 2.136(8) Å; 2: Ti‐O 1.902(9), Ti‐N2.252(8) Å) and have a single absorption band in the visible region of the UV‐spectrum. The exchange of the thf‐ligands in 1 by pyridine (in high molar excess) seems to be hindered as deduced from UV‐spectroscopy.
The Equilibrium Partial Pressure of HgI2 over and Thermodynamic Properties of Hg3Te2I21)
Authors: Hutchins Mark A. , Wiedemeier Heribert
Published: December 2005

The high temperature vaporization pattern of Hg3Te2I2(s,l) shows four distinctly different regimes, similar to those of the HgTe vaporization. The most predominant species in the vapor phase in all four regimes is HgI2(g), followed by Hg(g) and, possibly, Te2I2(g).

The width of the “homogeneity range” of Hg3Te2I2(s) was determined to be less than about 0.17 mole‐% HgI2. Applying the second‐law method to the vaporization of HgTe‐saturated Hg3Te2I2(s) at higher temperatures yields the heat and entropy of vaporization of 20.9 ± 2.3 (kcal/mole) and of 27.5 ± 2.8 (cal/mole K), respectively, with estimated total uncertainties of less than ± 5.8 (kcal/mole) and ± 7.6 (cal/mole K), at an average temperature of 722 K. With an estimated heat capacity function of Hg3Te2I2(s) and estimated thermodynamic values for HgI2‐saturated HgTe(s), the heat of formation and absolute entropy of Hg3Te2I2(s) are computed to be ${\rm \Delta}{\rm H}{\rm ^{o}_{298}}_{f}$ = −49.7 ± 1.1 (kcal/mole) and ${\rm \Delta}{\rm H}{\rm ^{o}_{298}}$ = 97.3 ± 1.4 (cal/mole K), with estimated total uncertainties of ± 8.3 (kcal/mole) and ± 14.0 (cal/mole K). The combined results of this investigation provide valuable information for the crystal growth of this material from the vapor and molten phase.
Structural Variations in the Solid‐Solution Series LnxCa2−xAl[Al1+xSi1−xO7] with 0 ≤ x ≤ 1 and Ln = La, Eu, Er
Authors: Peters Lars , Knorr K. , Depmeier W.
Published: December 2005

Gehlenite, Ca2Al[AlSiO7], has melilite‐type structure with space group $P{\bar 4}{\rm 2}{\rm _{1}}m$. It contains two topologically distinct positions coordinated tetrahedrally by oxygen. One is completely occupied by Al3+, whereas the other one contains Al3+ and Si4+. Normally, the Al3+ molar fraction in the second tetrahedrally coordinated position does not exceed xAl = 0.5, i.e. the so‐called Loewenstein‐rule is obeyed. In this contribution the structural variations in the melilite‐type compounds of the compositions LaxCa2−xAl[Al1+xSi1−xO7], EuxCa2−xAl[Al1+xSi1−xO7] and ErxCa2−xAl[Al1+xSi1−xO7] are discussed. All members of the solid solution except the end‐members violate Loewenstein's rule. Rietveld refinements against X‐ray powder diffraction patterns confirm that the compounds have space group $P{\bar 4}{\rm 2}{\rm _{1}}m$, without changes in the Wyckoff‐positions of the ions compared to gehlenite.
Hochdrucksynthese von BaSr2P6N12 und BaCa2P6N12 und Strukturvergleich der Reihe BaP2N4, BaCa2P6N12 und BaSr2P6N12
Authors: Karau Friedrich , Schnick Wolfgang
Published: December 2005

High‐Pressure Synthesis of BaSr2P6N12 and BaCa2P6N12 and Comparison of the Structures of BaP2N4, BaCa2P6N12, and BaSr2P6N12

The novel nitridophosphates BaCa2P6N12 and BaSr2P6 N12 were obtained by means of high‐pressure high‐temperature synthesis utilizing the multianvil technique (1200 °C, 5 GPa). The complex anion [PN2−] of the title compound is formally isoelectronic with silica. The crystal structure was solved from powder data and refined by the Rietveld method (BaCa2P6N12: $Pa{\bar 3}$, Z = 4, a = 9,9578(2) Å; BaSr2P6N12: $Pa{\bar 3}$, Z = 4, 10,0705(2) Å). The crystal structures are derived from that of BaP2N4 which is isotypic with a high pressure phase of CaB2O4 and BaGa2S4. For each compound the 31P solid state NMR spectrum yielded a single resonance (BaCa2P6N12: 7.4 ppm; BaSr2P6N12:3.9 ppm).
Substituted Ferrocenylboranes – Potential Ligand Precursors for ansa‐ Metallocenes, Constrained Geometry Complexes and ansa‐Diamido Complexes
Authors: Braunschweig Holger , Breitling Frank M. , Kraft Katharina , Kraft Mario , Seeler Fabian , Stellwag Sascha , Radacki Krzysztof
Published: December 2005

A wide range of potential ligand precursors and related compounds have been synthesized from ferrocenyldibromoborane and ferrocenylenebis(dibromoborane) via salt elimination reactions. These comprise ligand precursors suitable for the preparation of (i) ansa‐metallocenes such as [FcB(η1‐C5H5)2] (2), [FcB(1‐C9H7)2] (3), [FcB(3‐C9H7)2] (4) and [1,1′‐fc{B(3‐C9H7)2}2] (11), (ii) constrained geometry complexes such as [FcB(1‐C9H7)N(H)Ph] (7) and [FcB(3‐C9H7)N(H)Ph] (8), (iii) ansa‐diamido complexes such as [FcB(N(H)Ph)2] (9) as well as (iv) the related compounds [FcB(Br)N(H)tBu] (5), [FcB(Br)N(H)Ph] (6), [1,1′‐fc{B(Br)N(SiMe3)2}2] (12) and [1,1′‐fc{B(Br)NiPr2}2] (13) (Fc = ferrocenyl, fc = ferrocenylene, C5H5 = cyclopentadienyl, C9H7 = indenyl). All new compounds have been characterised by multinuclear NMR spectroscopic techniques and in the case of 7 and 12 by X‐ray diffraction methods.
Stabilization of Highly Reactive “Naked Anions”: Synthesis, Crystal Structure and Vibrational Spectrum of [Na(12‐crown‐4)2]2 [P2S6] · CH3CN
Authors: Gjikaj Mimoza , Brockner Wolfgang , Adam Arnold
Published: December 2005

The novel thiodiphosphate, [Na(12‐crown‐4)2]2[P2S6] · CH3CN, bis[di(12‐crown‐4)sodium] hexathiodiphosphate(V) acetonitrile solvate (1) has been synthesized by the reaction of Na2[P2S6] with 12‐crown‐4 in dry acetonitrile. The title compound crystallizes in the tetragonal space group P42/mbc (no. 135), with a = 15.184(1) Å, c = 21.406(2) Å and Z = 4 and final R1 = 0.0671 and wR2 = 0.0809. The crystal structure is characterized by discrete sodium‐bound crown‐ether sandwich cations, [Na(12‐crown‐4)2]+ and [P2S6]2− ions with D2h symmetry. Sodium ion is coordinated by the eight oxygen atoms of two crown‐ether molecules to form a square antiprisma. Solvent molecules of CH3CN are statistically disordered. Distances and angles of the [P2S6]2− unit are similar to those in [K(18‐crown‐6)]2 [P2S6] · 2 CH3CN, and in K2[P2S6] and Cs2[P2S6]. The FT‐Raman and FT‐IR spectrum of the title compound has been recorded and interpreted, especially with respect to the P2S6 group and in comparison to the few known metal hexathiodiphosphates(V).
Terminally Dimetallated N,N′‐Dimethylpiperazines with Doubly Spirocyclic Structures
Authors: Tian Xin , Fröhlich Roland , Mitzel Norbert W.
Published: December 2005

Dilithiated N,N′‐dimethyl‐piperazine, LiCH2N(CH2CH2)2 NCH2Li (2) was prepared by transmetallation of N,N′‐bis(trimethylstannylmethyl)‐piperazine (1) with nBuLi and was isolated as a highly pyrophoric yellowish powder in high yield. Compound 2 was characterized by elemental analysis and was reacted as difunctional aminomethylating reagent with dialkyl‐earth metal chlorides, R2MCl (M = Al, Ga; R = Me, tBu) which resulted in the formation of spirocyclic adducts of N,N′‐bis(dialkylmetallamethyl)‐piperazine and unreacted dialkylmetal chlorides, [(Me2AlCl)Me2AlCH2N(CH2CH2)2NCH2AlMe2(ClAlMe2)] (3) and [(tBu2GaCl)tBu2GaCH2N(CH2CH2)2NCH2GatBu2(ClGatBu2)] (4) with five‐membered rings. Compounds 1, 3 and 4 were identified by NMR‐spectroscopy (1H, 13C, 119Sn for 1, 27Al for 3), mass spectra (EI, for 1) and by crystal structure determinations.
Pr10[Si10−xAlxO9+xN17−x]Cl with x ≈ 1 – an Oxonitridoaluminosilicate Chloride
Authors: Lieb Alexandra , Lauterbach Rainer , Schnick Wolfgang
Published: December 2005

The oxonitridoaluminosilicate chloride Pr10[Si10−xAlxO9+xN17−x]Cl was obtained by the reaction of praseodymium metal, the respective chloride, AlN and Al(OH)3 with “Si(NH)2” in a radiofrequency furnace at temperatures around 1900 °C. The crystal structure was determined by single‐crystal X‐ray diffraction (Pbam, no. 55, Z = 2,a = 10.5973(8) Å, b = 11.1687(6) Å, c = 11.6179(7) Å, R1 = 0.0337). The sialon crystallizes isotypically to the oxonitridosilicate halides Ce10[Si10O9N17]Br, Nd10[Si10O9N17]Br and Nd10[Si10O9N17]Cl, which represent a new layered structure type. The structure refinement was performed utilizing an O/N‐distribution model according to Paulings rules, i.e. nitrogen was positioned on all bridging sites and mixed O/Noccupation was assumed on the terminal sites resulting in charge neutrality of the compounds. The Si and Al atoms were refined equally distributed on their three crystallographic sites, due to their poor distinguishability by X‐ray analysis. The tetrahedra layers of the structure consist of condensed [(Si,Al)N2(O,N)2] and [(Si,Al)N3(O,N)] tetrahedra of Q2 and Q3 type. The chemical composition of the compound was derived from electron probe micro analyses (EPMA).
Unusual Coordination Modes of Tris(pyrazol‐1‐yl)borates: Synthesis and Solid State Structures of Sodium[(dimethylamino)tris(pyrazol‐1‐yl)borate], Potassium[(dimethylamino)tris(pyrazol‐1‐yl)borate], and Potassium[phenyltris(pyrazol‐1‐yl)borate]
Authors: Bieller Susanne , Bolte Michael , Lerner Hans‐Wolfram , Wagner Matthias
Published: December 2005

We report the optimized syntheses and the solid state structures of the alkali metal tris(pyrazol‐1‐yl)borates M[Me2NBpz3] (M = Na+ (1), K+ (2); pz = pyrazol‐1‐yl) and K[PhBpz3] (3). Even though 1 and 2 consist of polymeric chains in the solid state, it is possible to identify subunits where the [Me2NBpz3]− ion acts as tridentate ligand towards Na+ and K+ and binds via two of its pyrazolyl rings and its dimethylamino nitrogen atom (κ3Npz,Npz,NNMe). In 3, the ligand [PhBpz3]− employs two pyrazolyl donors and the π‐face of its phenyl substituent for potassium coordination (κ3N,N,C).
Synthesis and Characterization of Two Open‐Framework Germanates containing Double Four‐Ring Building Units
Authors: Lin Zhi‐En , Zheng Shou‐Tian , Yang Guo‐Yu
Published: December 2005

Two new organically templated germanates, [GeO2]10·C2N2H8·H2O (1) and [GeO2]10·C3N2H10·H2O (2) have been synthesized under solvothermal conditions. The two compounds are isostructural and have three‐dimensional open‐framework architectures built up from Ge8O20 double four‐ring units and GeO4 tetrahedra. These building units are connected in such a way that they form a zeolite‐like porous framework with large 12‐ring channels along the [001] direction, where the organic amines reside.
Re‐evaluation of the X‐ray Crystal Structure of [Ta4F20] and the Synthesis and Characterization of a Series of Mixed‐Metal Pentafluorides of Niobium and Tantalum
Authors: Brewer Stuart A. , Brisdon Alan K. , Fawcett John , Holliman Peter J. , Holloway John H. , Hope Eric G. , Russell David R.
Published: December 2005

The direct fluorination of intimately mixed niobium and tantalum powders gives a range of mixed‐metal pentafluorides [NbxTa4‐xF20] (x = 1 2, 2 3, 3 4) as discreet species isostructural with tantalum pentafluoride (x = 0 1). The crystal structures of 1–4 are indistinguishable by X‐ray crystallography. Complex 1 crystallizes in the monoclinic space group C2/m with a = 9.5462(13), b = 14.3578(19), c = 5.0174(7) Å, β = 97.086(2)°, Z = 2. The geometry about the tantalum atom is distorted octahedral with 2 short and 2 slightly longer Ta‐Fterminal, and 2 Ta‐Fbridging distances. The angles at the bridging fluorine atoms are 172.9(5)°.
Cyanidverbrückte Koordinationspolymere aus cis‐ oder trans‐[Ru(tBuNC)4(CN)2] und MnCl2: Zum Einfluß unterschiedlicher Topologien auf die magnetischen Eigenschaften von Materialien
Authors: Halbauer Kathi , Leibeling Guido , Imhof Wolfgang
Published: December 2005

Cyanide Bridged Coordination Polymers from cis‐ or trans‐[Ru(tBuNC)4(CN)2] and MnCl2: About the Influence of Different Topologies on the Magnetic Properties of Materials

The reaction of cis‐ or trans‐[Ru(tBuNC)4(CN)2] with MnCl2 as an additional transition metal fragment yields the one dimensional coordination polymers {cis‐[Ru(CN)2(tBuNC)4] MnCl2}n, (1), and {trans‐[Ru(CN)2(tBuNC)4]MnCl2}n, (2), with a different arrangement of the metal centers caused by the different stereochemistry of the starting compounds. The variation of the Ru‐C‐N‐Mn geometry nevertheless leads to significant differences in the magnetic properties of 1 and 2. The coordination polymer derived from trans‐[Ru(tBuNC)4(CN)2] shows a more efficient antiferromagnetic intrachain interaction between the manganese centers compared to the cis‐derivative.
Synthese und Charakterisierung neuer intramolekular stickstoffstabilisierter Organoaluminium‐ und Organogalliumalkoxide
Authors: Schumann Herbert , Dechert Sebastian , Girgsdies Frank , Heymer Bernd , Hummert Markus , Hyeon Ji‐Young , Kaufmann Jens , Schutte Stefan , Wernik Sonja , Wassermann Birgit C.
Published: December 2005

Synthesis and Characterization of New Intramolecularly Nitrogen‐stabilized Organoaluminium‐ and Organogallium Alkoxides

The intramolecularly nitrogen stabilized organoaluminium alkoxides [Me2Al{μ‐O(CH2)3NMe2}]2 (1a), Me2AlOC6H2(CH2NMe2)3‐2,4,6 (2a), [(S)‐Me2Al{μ‐OCH2CH(i‐Pr)NH‐i‐Pr}]2 (3a) and [(S)‐Me2Al{μ‐OCH2CH(i‐Pr)NHCH2Ph}]2 (4) are formed by reacting equimolar amounts of AlMe3 and Me2N(CH2)3OH, C6H2[(CH2NMe2)3‐2,4,6]OH, (S)‐i‐PrNHCH(i‐Pr)CH2OH, or (S)‐PhCH2NHCH(i‐Pr)CH2OH, respectively. An excess of AlMe3 reacts with Me2N(CH2)2OH, Me2N(CH2)3OH, C6H2[(CH2NMe2)3‐2,4,6]OH, and (S)‐i‐PrNHCH(i‐Pr)CH2OH producing the “pick‐a‐back” complexes [Me2AlO(CH2)2NMe2](AlMe3) (5), [Me2AlO(CH2)3NMe2](AlMe3) (1b), [Me2AlOC6H2(CH2NMe2)3‐2,4,6](AlMe3)2 (2b), and [(S)‐Me2AlOCH2CH(i‐Pr)NH‐i‐Pr](AlMe3) (3b), respectively. The mixed alkyl‐ or alkenylchloroaluminium alkoxides [Me(Cl)Al{μ‐O(CH2)2NMe2}]2 (6) and [{CH2=C(CH3)}(Cl)Al{μ‐O(CH2)2NMe2}]2 (8) are to obtain from Me2AlCl and Me2N(CH2)2OH and from [Cl2Al{μ‐O(CH2)2NMe2}]2 (7) and CH2=C(CH3)MgBr, respectively. The analogous dimethylgallium alkoxides [Me2Ga{μ‐O(CH2)3NMe2}]2 (9), [(S)‐Me2Ga{μ‐OCH2CH(i‐Pr)NH‐i‐Pr}]n (10), [(S)‐Me2Ga{μ‐OCH2CH(i‐Pr)NHCH2Ph}]n (11), [(S)‐Me2Ga{μ‐OCH2CH(i‐Pr)N(Me)CH2Ph}]n (12) and [(S)‐Me2Ga{μ‐OCH2(C4H7NHCH2Ph)}]n (13) result from the equimolar reactions of GaMe3 with the corresponding alcohols. The new compounds were characterized by elemental analyses, 1H‐, 13C‐ and 27Al‐NMR spectroscopy, and mass spectrometry. Additionally, the structures of 1a, 1b, 2a, 2b, 3a, 5, 6 and 8 were determined by single crystal X‐ray diffraction.
Eine neue Synthese für Nitrosyl‐Salze mit schwach koordinierenden Anionen am Beispiel von NO[B(CF3)4]
Authors: Bernhardt Eduard , Finze M. , Willner Helge
Published: December 2005

A New Synthesis for Nitrosyl Salts with Weakly Coordinating Anions Exemplified by NO[B(CF3)4]

A new synthesis for nitrosyl salts of weakly coordinating anions is described, using the corresponding guanidinium salts as starting materials. The guanidinium salt [C(NH2)3][B(CF3)4] was obtained by a metathesis reaction of K[B(CF3)4] with [C(NH2)3]Cl. Treatment of the guanidinium salt with liquid NO2 resulted in analytical pure NO[B(CF3)4] in quantitative yield. The guanidinium and nitrosyl tetrakis(trifluormethyl)borates were characterized by vibrational and NMR spectroscopy as well as by DSC measurements.
Repetitive fishing, local depletion, and fishing efficiencies in the Kerguelen Islands fisheries
Authors: Bez N. , De Oliveira E. , Duhamel G.
Published: January 2006

Commercial catch per unit effort (cpue) recorded by observers on board trawlers operating in the French EEZ around the Kerguelen Islands (south Indian Ocean) are used to analyse the impact of repetitive fishing on cpues and to estimate local fishing efficiencies. Series of cpues from the same fishing locations and no more than two days apart are first built, and then the mean depletion effect of repetitive fishing (between 4% and 10% for Patagonian toothfish and around 20% for icefish and marbled notothen) is quantified. Random fluctuations of cpues around an exponential decrease (i.e. the reference model when fishing efficiencies are constant) lead to modelling fishing efficiency as a random variable. Based on the observations of the ratio between two consecutive catches, a method is developed to estimate the probability density function of fishing efficiencies. The significant decrease of average fishing efficiency between the start of the fishery and its full exploitation phase is explained by a change in regulations (from global to individual quotas).
Action variety of planners: Cognitive load and requisite variety
Authors: Fransoo Jan C. , Wiers Vincent C.S.
Published: January 2006

The complexity of planning tasks have increased over the past decade. There is relatively poor understanding what the implications are of increased task complexity in planning and scheduling operations. Previous work in the behavioral sciences have investigated the concept of cognitive load, addressing both task complexity and task workload or stress, and have concluded that decision makers tend to resort to routine action and reduce the variety in their actions with increasing complexity and workload. Alternatively, control theory suggests that a higher variety of actions is needed to deal with more complex problems. In this paper, we investigate the effects of task complexity in a chemical plant on the variety of actions deployed by the planners. The single work center resource structure and the availability of actual planning data from an MRP‐application database allows us to both use field data and study a situation which is simple enough to measure the main effect. Our results suggest that increased task complexity without time pressure does indeed lead to increased action variety deployed by the planners.
Relativistic electron events in 2002: Studies of pitch angle isotropization
Authors: Kanekal S. G. , Friedel R. H. W. , Reeves G. D. , Baker D. N. , Blake J. B.
Published: December 2005

Energization of electrons to relativistic energies in the Earth's outer radiation belt is not fully understood. Recent renewed interest in the problem has resulted in a number of models which invoke a variety of physical processes ranging from diffusive particle transport to in situ acceleration. Evolution of local pitch angle distributions and global flux isotropization timescales of relativistic electrons may be important discriminators of the underlying physical processes of energization, transport, and loss. Data from SAMPEX, Polar, and LANL suite of satellites were used to study electron isotropization and pitch angle evolution for relativistic electron enhancement events during the year 2002. It was found that during electron energization events there is generally increased precipitation of electrons and rapid electron flux isotropization on a global scale. Case studies using pitch angle resolved data collected at geosynchronous distances suggest an in situ broadening of the local pitch angle distribution in agreement with the corresponding global isotropization measurements. These observations suggest that electron energization in the magnetosphere is intimately associated with rapid pitch angle scattering leading to a flattening of the pitch angle distributions of energized electrons.
Lightning activity in the eastern Mediterranean region
Authors: Defer E. , Lagouvardos K. , Kotroni V.
Published: December 2005

Twenty days of lightning activity recorded during winter 2002–2003 in the Mediterranean region with significant rain accumulation in Greece were studied on the basis of the measurements of the UK Met Office long‐range VLF sferics Arrival Time Difference (ATD) system and the spaceborne NASA Lightning Imaging Sensor (LIS) sensor onboard the Tropical Rainfall Measurement Mission (TRMM) satellite. Cloud‐to‐Ground (CG) flash density as well as history of CG activity were investigated on the basis of the sferics fixes. LIS observations were studied to document both intracloud (IC) and CG flashes in terms of extension, duration and development during different TRMM passes over the Mediterranean Sea. The analysis revealed that more than 266,000 CG flashes occurred during the 20 studied days. CG flashes were mostly located over sea, and CG density was found to follow the North African and Turkish shorelines. About 85% of the CG flashes were composed of a single sferics fix while the number of sferics fixes per CG flash was found ranging up to 15. Flash duration was found ranging from a few milliseconds to 2 s on the basis of LIS observations.
Chemical heterogeneity in diffusion‐dominated aquitards
Authors: Harrington Glenn A. , Hendry M. Jim
Published: December 2005

High‐resolution measurements of the three‐dimensional (3‐D) variability in pore water electrical conductivity (EC) were obtained at a clay‐rich aquitard research site (the King site, 120 m × 70 m area) in southern Saskatchewan, Canada, using direct‐push probing technology (n = 35 boreholes). These measurements revealed complex lateral heterogeneity in the subsurface salt distributions which raised questions on the validity of the commonly used approach of transposing chemical data from distributed piezometers onto 1‐D depth profiles for interpretation and solute transport modeling. Two‐dimensional numerical modeling simulations demonstrated that distributed, nonuniform salt inputs have existed at the top of the unoxidized till aquitard for the past 3–5 kyr. The source of the nonuniform salt inputs is unclear but may be due to either variations in microtopography (<0.5 m) or variable penetration depth of surface fractures. A suite of generic solutions was developed to estimate the critical depth required to obtain chemical homogeneity in aquitards with nonuniform solute inputs and diffusion as the dominant transport mechanism. These solutions are presented for a range of sinusoidal input functions with varying amplitudes, magnitudes, and wavelengths. The solutions indicate EC distributions at the King site should be laterally uniform below a depth of around 20 m BG, which is consistent with observed EC values at the site. This study shows that aquitards with nonuniform salt inputs at their upper boundary are chemically heterogeneous above some critical depth and thus require careful attention when modeling solute transport processes within them.
Mini‐magnetosphere over the Reiner Gamma magnetic anomaly region on the Moon
Authors: Kurata M. , Tsunakawa H. , Saito Y. , Shibuya H. , Matsushima M. , Shimizu H.
Published: December 2005

We show presence of a mini‐magnetosphere above the Reiner Gamma magnetic anomaly (RGA) region in the solar wind, using Lunar Prospector magnetometer (MAG) measurement data. RGA is one of the strongest magnetic anomalies on the Moon. Two magnetic anomalies are found from six MAG datasets at 17–40 km altitudes in the lunar wake or the geomagnetic tail lobe and are well explained by a two‐dipole model. When RGA was exposed to the solar wind plasma, two MAG datasets were obtained at 27–29 km altitudes. Although the magnetic anomalies survived against the plasma pressure, they were heavily distorted in comparison with the magnetic field of the two‐dipole model. Flow directions and dynamic pressures of the solar wind plasma at those periods indicate that the distortions were caused by forming a mini‐magnetosphere over the RGA region in the solar wind.
The spatial and temporal variability of the East Greenland Coastal Current from historic data
Authors: Wilkinson David , Bacon Sheldon
Published: December 2005

Analysis of historic hydrographic data collected between 1932 and 1997 show a freshwater jet flowing southward along the East Greenland Shelf between Denmark Strait and Cape Farewell with a typical baroclinic transport of between 0.5 and 2 Sv. This jet has been labelled the East Greenland Coastal Current (EGCC). The depth of the jet is a function of transport but the lateral extent of the jet is mainly defined by the position of the shelf break. Comparing section transports from different times and locations it is seen that significant short‐term variability masks both longer‐term variability and latitudinal variations. The data suggest an increase in EGCC transport during the early 1930s Greenland warm period followed by reduced average fluxes thereafter but there is insufficient data for this result to be considered statistically significant. In addition there is no evidence of significant growth in the transport as the jet progresses south as might be expected with the addition of run‐off from the SE Greenland fjords.
Observational evidence for exponential tornado intensity distributions over specific kinetic energy
Authors: Dotzek Nikolai , Kurgansky Michael V. , Grieser Jürgen , Feuerstein Bernold , Névir Peter
Published: December 2005

Observational evidence supports the recent analytical prediction that tornado intensities are exponentially distributed over peak wind speed squared (v2), or equivalently, Rayleigh‐distributed over v. For large USA data samples, exponential tails are found in the tornado intensity distributions over v2 from about F2 intensity on. Similar results follow for smaller worldwide data samples. For the 1990s data from the USA and Oklahoma, deviations from the Rayleigh distribution for weak tornadoes can be explained by the emergence of a separate, likely non‐mesocyclonic tornado mode. These bimodal datasets can be modeled by superposition of two Rayleigh distributions. The change in modal dominance occurs at about the F2 threshold (v ≈ 50 m s−1). In France, likely mainly the mesocyclonic tornado mode has been recorded, while in the UK, only a non‐mesocyclonic mode seems to be present.