bluuebunny/crossref_metadata_2025 huggingface dataset:
Voltage-controlled epitaxial strain in La0.7Sr0.3MnO3∕Pb(Mg1∕3Nb2∕3)O3-PbTiO3(001) films
Authors: Thiele C. , Dörr K. , Fähler S. , Schultz L. , Meyer D. C. , Levin A. A. , Paufler P.
Published: December 2005

Epitaxially grown La0.7Sr0.3MnO3 thin films show resistance modulations induced by the inverse piezoeffect of the employed Pb(Mg1∕3Nb2∕3)O3-PbTiO3(001) (PMN-PT) substrates. The in-plane strain state of the films can continuously be tuned by application of a piezovoltage to PMN-PT. The lattice deformation of a PMN-PT(001) substrate was quantified by x-ray measurements under an electric field. Variation of in-plane lattice parameters by ∼0.06% reversibly changes the resistance of the manganite films by up to 9% at 300 K and shifts the magnetic Curie temperature. Films of different thicknesses from 50 to 290 nm, offering different as-grown strain states, have been studied.
Neutral ion-implantation-induced selective quantum-dot intermixing
Authors: Djie H. S. , Ooi B. S. , Aimez V.
Published: December 2005

High spatial band-gap tuning has been observed from an InGaAs∕GaAs quantum-dot (QD) structure implanted with electrically neutral species, As and P ions, at 200°C followed by a rapid thermal annealing. Phosphorous was found to be a more effective species to induce QD intermixing than the As at similar dose level. A blueshift as large as 126meV has been observed from the P+-implanted and intermixed sample, while only ∼14meV has been measured from the SixNy-capped sample.
Ultrascaled hafnium silicon oxynitride gate dielectrics with excellent carrier mobility and reliability
Authors: Quevedo-Lopez M. A. , Krishnan S. A. , Kirsch P. D. , Pant G. , Gnade B. E. , Wallace R. M.
Published: December 2005

A hafnium silicon oxynitride gate dielectric with a universal channel mobility of ∼90% at 1MV∕cm, equivalent oxide thickness of approximately 1nm, and leakage current 200× less than SiO2 is reported. X-ray photoelectron spectroscopy results suggest that the small peak mobility loss observed in scaled HfSiON may be attributed to increased Si–N bonding near the silicon interface. In accordance with these mobility results, the Si–N:Hf–N bond ratio decreases with increasing HfSiON physical thickness. Threshold voltage instability at 1nm equivalent oxide thickness is less than 10mV after a 1000s stress at 22MVcm. ΔVTH monotonically increases with HfSiON physical thickness. This is associated with greater crystallization in thicker HfSiON films.
Polarization reversal of ferroelectric small particles: Surface polarization enhancement and bound charges effects
Authors: Baudry Laurent
Published: December 2005

The polarization reversal mechanism in ferroelectric small particles with surface polarization enhancement has been theoretically investigated. The model based on a thermodynamical approach, in which the bound charges contribution has been included, predicts, as it does for polarization decreases towards the surface, a reversal current curve with one peak. This result is very different from that previously obtained within the uniform electric field approximation for which the current curve exhibited two peaks.
Carrier dynamics in laterally strain-modulated InGaAs quantum wells
Authors: Talalaev Vadim , Tomm Jens W. , Elsaesser Thomas , Zeimer Ute , Fricke Jörg , Knauer Arne , Kissel Heiko , Weyers Markus , Tarasov Georgiy G. , Grenzer J. , Pietsch U.
Published: December 2005

We investigate the transient recombination and transfer properties of nonequilibrium carriers in an In0.16Ga0.84As∕GaAs quantum well (QW) with an additional lateral confinement implemented by a patterned stressor layer. The structure thus contains QW- and quantum-wire-like areas. At low excitation densities, photoluminescence (PL) transients from both areas are well described by a rate equation model for a three-level system with a saturable interlevel carrier transfer representing the lateral drift of carriers from the QW regions into the wires. Small-signal carrier lifetimes for QW, wires, and transfer time from QW to wire are 180, 190, and 28 ps, respectively. For high excitation densities the time constants of the observed transients increase, in agreement with the model. In addition, QW and wire PL lines merge indicating a smoothening of the potential difference, i.e., the effective carrier confinement caused by the stressor structure becomes weaker with increasing excitation.
Improved breakdown voltage and impact ionization in InAlAs∕InGaAs metamorphic high-electron-mobility transistor with a liquid phase oxidized InGaAs gate
Authors: Lee Kuan-Wei , Yang Nan-Ying , Houng Mau-Phon , Wang Yeong-Her , Sze Po-Wen
Published: December 2005

The In0.52Al0.48As∕In0.53Ga0.47As metal-oxide-semiconductor metamorphic high-electron-mobility transistors (MOS-MHEMTs) with a thin InGaAs native oxide layer (∼10–15nm) are demonstrated. The gate dielectric is directly obtained by oxidizing InGaAs material in a liquid phase solution. As compared to its counterpart MHEMTs, the MOS-MHEMTs have larger gate swing voltages, higher gate-to-drain breakdown voltages, and lower gate leakage currents with the suppressed impact ionization effect due to its higher barrier height.
Vacuum level alignment at organic/metal junctions: “Cushion” effect and the interface dipole
Authors: Witte Gregor , Lukas Simon , Bagus Paul S. , Wöll Christof
Published: December 2005

The electronic level alignment of various organic molecules on metal surfaces has been determined by a combined experimental and theoretical effort. Using ab initio electronic structure calculations, it is demonstrated that the commonly observed interface dipole is largely due to a quantum-mechanical phenomenon resulting from exchange repulsion. Surprisingly, this physical effect, also referred to as Pauli repulsion dominates even in the case of aromatic molecules on Cu and Au surfaces, i.e., on interfaces that are of key importance in molecular electronics.
Investigation of silicon-germanium fins fabricated using germanium condensation on vertical compliant structures
Authors: Liow Tsung-Yang , Tan Kian-Ming , Yeo Yee-Chia , Agarwal Ajay , Du Anyan , Tung Chih-Hang , Balasubramanian Narayanan
Published: December 2005

We report the formation of defect-free SiGe vertical heterostructures using Ge condensation on vertical SiGe structures. To evaluate the effectiveness of substrate compliance in vertical structures, SiGe fins of various widths were subjected to Ge condensation. This formed vertical fin heterostructures comprising a SiGe core region sandwiched by Ge-rich regions. Using cross-sectional transmission electron microscopy (TEM), wide fins were found to contain more dislocations than narrower fins, in which we observed few or no dislocations. Lattice strain analysis using high-resolution TEM image analysis was used to confirm that strain relaxation has occurred. In the wide fins (noncompliant substrate), strain relaxation was dislocation mediated. In the narrow fins, substrate compliance enabled strain relaxation in the Ge-rich layer with reduced dislocation formation. Hence, we also demonstrated the formation of a strain-relaxed homogeneous SiGe fin (∼90% Ge concentration) with no observable dislocations.
Nucleation of InN quantum dots on GaN by metalorganic vapor phase epitaxy
Authors: Lozano J. G. , Sánchez A. M. , García R. , González D. , Araújo D. , Ruffenach S. , Briot O.
Published: December 2005

InN quantum dots (QDs) on GaN (0001) grown by metalorganic vapor phase epitaxy onto a sapphire substrate were studied by transmission electron microscopy (TEM). We found that the nucleation of InN QDs on GaN is directly related to the presence of threading dislocations (TDs) in the center of the QDs. The TEM analysis revealed that the TDs finish at the InN∕GaN interface and they are pure edge dislocations. Therefore, spiral growth models cannot explain nucleation of these QDs. Although controlling edge TDs constitute a possible approach to determine the QD density, a better approach may be an increase in the material growth rate in order to enter the diffusion-limited growth mode, where growth is not sensitive to surface heterogeneities.
Role of structural defects on exchange bias in the epitaxial CoO∕Co system
Authors: Ghadimi M. R. , Beschoten B. , Güntherodt G.
Published: December 2005

We have studied the influence of nonmagnetic defects throughout the antiferromagnet Co1−yO on the exchange bias (EB) in epitaxially grown Co1−yO∕Co bilayers. These defects are either substitutional or structural (twin boundaries and surface morphology), which both lead to an increase of the EB field. We find a dominance of twin boundaries over surface morphology (roughness) in enhancing EB that is consistent with the domain state model for exchange bias. In contrast, the crystal orientation of the Co1−yO layer does not show a significant effect on the EB in this system.
Scaling of micro- and nanodevices actuated by Casimir forces
Authors: Bárcenas J. , Reyes L. , Esquivel-Sirvent R.
Published: December 2005

The effect of the Casimir force in micro- and nanoelectromechanical systems is examined taking fully into account the dielectric properties of the materials, as well as the finite thickness of movable elements in micro- and nanosystems. The resulting equations are exact, and from the bifurcation diagrams the critical separation before jump-to-contact is determined. It is shown how the critical separation changes, for example, with the dielectric properties of the materials and how these systems can be rescaled based on the information from the bifurcation diagrams.
Limitations of active carrier removal in silicon Raman amplifiers and lasers
Authors: Dimitropoulos D. , Fathpour S. , Jalali B.
Published: December 2005

The lifetime of two-photon generated carriers has been established as the critical parameter that determines the performance of silicon Raman lasers and amplifiers since it determines the optical loss. Here, we investigate the intensity dependence of the carrier lifetime in the case where the carriers are swept out by means of a p-n junction. Numerical simulations show that at sufficiently high pump intensities, the generated carriers screen the applied electric field and therefore result in a higher lifetime and hence a lower net Raman gain. We also quantify the electrical power dissipation necessary to maintain low optical losses.
Phase of reflection high-energy electron diffraction oscillations during (Ba,Sr)O epitaxy on Si(100): A marker of Sr barrier integrity
Authors: Norga G. J. , Marchiori C. , Guiller A. , Locquet J. P. , Rossel Ch. , Siegwart H. , Caimi D. , Fompeyrine J. , Conard T.
Published: December 2005

We use the reflection high-energy electron diffraction oscillation phase shift to monitor the stability of the Sr barrier, prepared by exposure of Si(100) to Sr at high temperatures, in situ during molecular beam epitaxy growth of (Ba,Sr)O on Si(100). Our results confirm that the deposition of additional metallic Sr at low temperature is essential for preventing the incorporation of the Sr termination layer in the (Ba,Sr)O layer during its growth, and for obtaining monolayer thin (Ba,Sr)O layers with good crystallinity and minimal density of interfacial Si–O bonds on Si(100).
Verification of the O–Si–N complex in plasma-enhanced chemical vapor deposition silicon oxynitride films
Authors: Naskar Sudipto , Wolter Scott D. , Bower Christopher A. , Stoner Brian R. , Glass Jeffrey T.
Published: December 2005

Silicon oxynitride films were deposited using a plasma-enhanced chemical vapor deposition process. The bond configurations of the constituent atoms in the deposited film were analyzed using x-ray photoelectron spectroscopy. Analysis of the Si 2p spectra showed the presence of nonstoichiometric silicon oxide and silicon oxynitride. Analysis of the binding energy shifts induced by Si–O and Si–N bond formation indicated an O–Si–N complex was present in the film matrix. Component balance analysis indicated that second-nearest-neighbor bond interactions were not the cause of these energy shifts and supported the presence of an O–Si–N complex.
Charge transport effects in field emission from carbon nanotube-polymer composites
Authors: Smith R. C. , Carey J. D. , Murphy R. J. , Blau W. J. , Coleman J. N. , Silva S. R. P.
Published: December 2005

Electron field emission measurements have been made on multiwall arc discharge carbon nanotubes embedded in a conjugated polymer host. Electron emission at low nanotube content is observed and attributed to an enhancement of the applied electric field at the polymer/nanotube/vacuum interface where the electron supply through the film is attributed to fluctuation induced tunneling in a disordered percolation network. A high network resistance is attributed to a polymer coating surrounding each nanotube, resulting in high resistance nanotube-polymer-nanotube tunnel junctions. The potential use of carbon nanotube-polymer composites for field emission based displays is also discussed.
Demonstration of Rashba spin splitting in GaN-based heterostructures
Authors: Weber W. , Ganichev S. D. , Danilov S. N. , Weiss D. , Prettl W. , Kvon Z. D. , Bel’kov V. V. , Golub L. E. , Cho Hyun-Ick , Lee Jung-Hee
Published: December 2005

The circular photogalvanic effect, induced by infrared radiation, has been observed in (0001)-oriented n-GaN low dimensional structures. The photocurrent changes sign upon reversing the radiation helicity demonstrating the existence of spin splitting of the conduction band in k space in this type of materials. The observation suggests the presence of a sizeable Rashba type of spin splitting, caused by the built-in asymmetry at the AlGaN∕GaN interface.
Metal-wire terahertz time-domain spectroscopy
Authors: Walther Markus , Freeman Mark R. , Hegmann Frank A.
Published: December 2005

Terahertz (THz) pulses propagating on a metal-wire waveguide are used to perform terahertz time-domain spectroscopy of lactose powder dispersed on top of the wire. The THz pulses are generated by a photoconductive switch at one end of the metal wire and are detected at the other end by electro-optic sampling in a ZnTe crystal that can be moved parallel to the axis of the metal wire. A large enhancement in the peak amplitude of the THz signal is observed by contacting the metal wire to one of the electrodes of the photoconductive switch. The propagation characteristics of the THz pulse along the metal wire and near its end are studied. Potential applications of metal-wire terahertz time-domain spectroscopy are discussed.
Silicon waveguides produced by wafer bonding
Authors: Poulsen M. , Jensen F. , Bunk O. , Feidenhans’l R. , Breiby D. W.
Published: December 2005

X-ray waveguides are successfully produced employing standard silicon technology of UV photolithography and wafer bonding. Contrary to theoretical expectations for similar systems even 100μm broad guides of less than 80nm height do not collapse and can be used as one dimensional waveguides to excite single guided modes at typical x-ray energies.
One-dimensional Au∕Si heterojunction-microstructure and phase evolution under electron beam irradiation
Authors: Li Quan , Jiao Yang
Published: December 2005

A special type of Au∕Si nanowire heterojunctions, which are wrapped by SiO2 surface layer, is demonstrated in this work. Nanochannels exist in-between the Si-core∕SiO2-sheath close to the junction, which provides a flowing path for the Au at elevated temperatures. The Au–Si interactions during the reversible flowing process lead to an interesting phase evolution of the junction system, which eventually result in self-formation of the secondary nanostructures at the original Si∕SiO2 interface. The observed microstructure∕phase evolution of the Au–Si nanowire junction under the focused electron beam irradiation suggests an approach to modify and pattern the Si nanowire surface, which may have potential applications in the nanoelectronic industry.
Confinement of electromigration induced void propagation in Cu interconnect by a buried Ta diffusion barrier layer
Authors: Yan M. Y. , Tu K. N. , Vairagar A. V. , Mhaisalkar S. G. , Krishnamoorthy Ahila
Published: December 2005

Direct observation, by means of in situ scanning electron microscopy, of void heterogeneous nucleation and migration controlled electromigration failure mechanism in Cu dual damascene interconnect structures has been recently reported [A. V. Vairagar, S. G. Mhaisalkar, A. Krishnamoorthy, K. N. Tu, A. M. Gusak, M. A. Meyer, and E. Zschech, Appl. Phys. Lett. 85, 2502 (2004)] In the present study, a dual damascene structure with an additional 25nm Ta diffusion barrier embedded into the upper Cu layer was fabricated. This thin layer of diffusion barrier blocked voids from propagating into the via, thus eliminating the previously reported failure mechanism. With this structure, a lifetime improvement of at least 40 times was achieved. Analysis on failed samples suggested that failures in samples with the embedded Ta barrier layer occurred at the bottom of the via, which were caused by void migration along the bottom of the Cu lines.
A Synthesis of Conduramine B and a 'Condurithiol', useful Molecules for Studying the Inhibition of β-Xylosidases
Authors: McDonough Matthew J. , Stick Robert V. , Tilbrook D. Matthew G.
Published: December 2005

Conduramine B and a ‘condurithiol’, namely
(1S,2S,3R,6R)-6-aminocyclohex-4-ene-1,2,3-triol
and
(1R,2S,3R,6R)-6-sulfanylcyclohex-4-ene-1,2,3-triol,
have been prepared by the thermal rearrangement of an acetimidate and a
dithiocarbonate, respectively. Both the amine and the thiol are putative
inhibitors of β-xylosidases and, in order to mimic the natural substrate
more closely, an N- and an
S-pseudo-disaccharide have been prepared.
Experiments Directed Towards the Synthesis of Anthracyclinones. XXXII. Synthesis of Anthraquinone Aldehydes
Authors: Bercich Mark D. , Cambie Richard C. , Rutledge Peter S.
Published: December 2005

Syntheses of C2 anthraquinone aldehydes from the commercially availableanthraru¯n (1) have been investigated. A synthesis of the keto aldehyde(2) in nine steps and 73% overall yield was achieved. Syntheses of (2)exploiting selective oxidations of either a C-boundallyl group by Wacker oxidation to introduce the methyl keto functionality orof a C-bound prop-1-enyl moiety by dihydroxylation andoxidative cleavage to generate the C2 formyl group were also developed. Thealdehyde (27) was synthesized in seven steps and in 81% overall yieldfrom (1), and syntheses of the phenolic aldehydes (33), (34), and (35), the C1benzyloxy aldehyde (36) and the anthracene aldehyde (37) were also developed.
Invited Review. A Combinatorial Approach to the Development of Environmentally Benign Organic Chemical Preparations
Authors: Strauss Christopher R.
Published: December 2005

Enabling technologies and methodologies were established and combined to
afford various environmentally benign processes for laboratory-scale organic
synthesis and for the production of fine chemicals, intermediates and
pharmaceuticals. The technologies comprised continuous and batch microwave
reactors and catalytic membranes. The methodologies included solvent-free
conditions, catalysed or uncatalysed processes, the use of aqueous media at
high temperature and non-extractive techniques for product isolation.
Applications included Hofmann eliminations, Willgerodt and Jacobs–Gould
reactions, indole transformations, aldol condensation, Rupe and
Meyer–Schuster rearrangements and C–C coupling reactions
(including a tandem Heck coupling–dehydrogenation). New processes for
catalytic etherification, uncatalysed hydrogen transfer and a one-step
arylamidation were also developed. Typical products were
N-(4-hydroxyphenyl)acetamide, carvacrol,
a-phenylacetamide, cinnamaldehyde, cinnamyl alcohol, acetophenone, indole,
3-hydroxy-1,2-dimethyl-4-pyridone, di(2-phenylethyl) ether,
di(cyclopropylmethyl) ether, 3-methylcyclopent-2-enone and a synthetic
precursor of nalidixic acid.
Structure of Hydrated Copper(II) Colchiceine
Authors: Mackay Maureen F. , Gable Robert W. , Morrison James D. , Satzke Lothar O.
Published: December 2005

Hydrated crystals of copper(II) colchiceine belong to the tetragonal space
group P
432I2 with a 13·415(1),
c 50·169(8) Å and Z
8. The structure has been refined to a conventional R
factor of 0·077 for 4560 observed data. The tropolonic oxygens from two
colchiceine molecules are coordinated to the copper atom in this bis-chelated
complex to form a square planar arrangement. The sites of three of the waters
are clearly defined, but the others are disordered over seven partially
occupied sites. An intricate hydrogen-bonding system links the complex and
water molecules into a three-dimensional network in the
crystal.
Synthesis and hydroboration of lipophilic hydroxy-pyridinones and their complexes with molybdenum(VI)
Authors: Gagnon M. Karen J. , St. Germain Timothy R. , Vogels Christopher M. , McNamara Robert A. , Taylor Nicholas J. , Westcott Stephen A.
Published: December 2005

We have prepared four potentially lipophilic
N-substituted hydroxypyridinones containing unsaturated
hydrocarbon groups. The propyl vinyl ether derivative (3) has been
characterized by an X-ray diffraction study. Complexes of the type
cis-MoO2L2,
where L represents the hydroxypyridinonato ligands, have also been prepared.
The pyridinone ligands are bound to molybdenum in a cis
bidentate fashion via the deprotonated hydroxy groups and the ketone moieties.
Initial investigations into the hydroboration of the alkene groups in the
pyridinone ligands and corresponding metal complexes is presented. Crystals of
(3) are monoclinic, with a 10.466(1),
b 13.388(1), c 15.386(2) Å,
β 102.343(8)˚, Z 8, space group
P21/n.
Nickel complexation and photophysics of alkylanthracenyl dioxocyclam macrocycle derivatives
Authors: Boyd Simon , Cabral Nuno M. , Ghiggino Kenneth P. , Grannas Martin J. , McFadyen W. David , Tregloan Peter A.
Published: December 2005

Ligands H2L in which (10-R-anthracen-9-yl)methyl
moieties (R = H, Me, Et) are covalently joined (6-position) to the
5,7-dioxocyclam macrocycle framework have been prepared and their nickel(II)
complexes isolated and characterized. X-Ray crystal structures of
NiIIL (R = H, Me) complexes show that in both
structures the anthracene moieties are folded around towards the mean plane of
the macrocycles; dihedral angles between the mean anthracene and macrocyclic
planes of c. 22˚ are subtended.
1H n.m.r. spectrometry indicates that the folded
conformations are retained in solution. Absorption and fluorescence spectra,
fluorescence quantum yields and lifetimes of the anthracenyl macrocycles are
reported. Absorption spectra of the metal complexes are red-shifted and the
fluorescence is dramatically quenched compared to the metal-free compounds
indicating a strong electronic interaction between the anthracene and the
complexed dioxocyclam macrocycle.
Triple helical DNA formation by a hydrophobic oligonucleotide-peptide hybrid molecule
Authors: Guzzo-Pernell Nancy , Tregear Geoffrey W.
Published: December 2005

Stable triple helical DNA formation with triplex forming
oligonucleotide–peptide hybrids, containing hydrophobic peptides, has
previously been difficult to achieve. We report hereon stable triplexation
with an oligonucleotide–peptide hybrid containing a hydrophobic peptide.
The peptide of interest is the gp41b peptide, which is derived from the
hydrophobic terminal domain of the HIV transmembrane glycoprotein gp41.
Triplex forming oligonucleotides conjugated to the gp41b peptide were prepared
with and without intramolecular spacer linkers. Hybrids with appropriate
spacers formed stable triplexes whereas those without the linkers did not.
Oligonucleotide–peptide conjugates have several applications mainly in
control of gene expression, with the peptide enhancing intracellular delivery
of the oligonucleotide. The gp41b peptide is one of a number of candidate
peptides considered to be potential delivery vectors. Hence, the data
presented here may prove to be useful in designing such conjugates. Our data
also extend the list of DNA structures known to stabilize triplexes and
suggest that triplexation by oligonucleotide–peptide hybrids may be
peptide sequence dependent.
Structural Systematics of Rare Earth Complexes. XIII (‘Maximally’) Hydrated (Heavy) Rare Earth Nitrates
Authors: Kepert David L. , Junk Peter C. , Skelton Brian W. , White Allan H.
Published: December 2005

Room-temperature single-crystal X-ray structure determinations are known for a
number of ‘maximally hydrated" nitrates of, in particular, the
lighter lanthanoid elements; in all cases, all nitrates coordinate as
O,O′-bidentate ligands so
that the series may be represented at the outset as
Ln(O2NO)3.x
H2O. Two distinct triclinic P 1
hexahydrate phases of similar cell dimensions are recognized, the most
distinctive distinguishing feature being that in the La, Ce phase the
11-coordinate Ln is surrounded by three
O,O′-bidentate nitrate and
five O-unidentate water molecule ligands; the domain of
the other, with four coordinated water molecules, extends from Ln = Pr
to Ln = Dy (inclusive of Y). At local ambience, we have crystallized
heavier members of the series as pentahydrates, isomorphous with the
previously characterized Ln = Eu example, also containing a molecule of
the form
[Ln(O2NO)3(OH2)4]
(with a molecule of water of crystallization), but a different stereoisomer to
that found in the Ln = Pr(-)Dy array. Structure determinations are
recorded for Ln = Dy, Er, Yb, conventional R on
|F| 0·042, 0·034,
0·029 for No = 3858,
3980, 3935 independent ‘observed’ (I >
3σ(I)) diffractometer reflections. For Ln =
Lu a new tetrahydrate phase is described, monoclinic
P21/n, a
7·379(7), b 10·364(5),
c 14·26(1) Å, β 96·09(7)°,
Z = 4, R 0·048 for
No 2324, together with a new
triclinic P 1 trihydrate, a
12·591(4), b 12·144(3),
c 7·355(2) Å, α 80·22(2),
β 77·68(3), γ 62·30(2)°, Z
= 4, R 0·051 for
No 4552. In both of the latter, Lu
is nine-coordinate, with three bidentate nitrate groups and three coordinated
water molecules; remarkably, the two independent molecules of the asymmetric
unit in the triclinic phase are distinct isomers, one having the water
molecules fac, derivative of the 10-coordinate array of
the Pr(-)Yb series with quasi-3 symmetry, while the
other, like that in the monoclinic phase, is mer.
Structural Systematics of Rare Earth Complexes. XX (Maximally) Hydrated Rare Earth Sulfates and the Double Sulfates (NH4)Ln(SO4)2.4H2O (Ln = La, Tb)
Authors: Kepert Cameron J. , Junk Peter C. , Skelton Brian W. , White Allan H.
Published: December 2005

Room-temperature single-crystal X-ray studies carried out on trivalent rare
earth sulfate hydrates,
Ln2(SO4)3.xH2O,
crystallized at local ambience suggest the following arrays to be prevalent.
For Ln = La, the nonahydrate is found, hexagonal
P 63/m,
with conventional R on
|F| 0·023 for
No 1159 ‘observed’
(I >3σ(I)) diffractometer
reflections (redetermination). Although for Ln = Ce a similar structure
has been previously recorded, we have obtained that adduct as the monoclinic
C 2/c, Z
= 4, octahydrate, a phase also found for Ln = Lu and diverse
representative intermediate lanthanoids: a ≈
13·6, b ≈ 6·6, c
≈ 18·2 Å, β ≈ 102°; for Ln = Ce
(redetermination), Dy, Yb (redetermination), Lu, R was
0·022, 0·035, 0·031, 0·024 for
No 3279, 2127, 3008, 3325
respectively. The structures of two lower hydrates adventitiously obtained are
also recorded: the pentahydrate for Ln = Ce, monoclinic
C 2/c, a
15·741(3), b 9·632(3),
c 10·358(3) Å, β 119·72(2)°,
Z = 4, R 0·030 for
No 3372 (a redetermination), and
the trihydrate for Ln = Lu, orthorhombic
Cmc21, a
13·527(5), b 18·415(5),
c 9·242(7) Å, Z
= 8, R 0·040 for
No 1743. All structures are
infinite polymeric arrays, the lanthanoid atoms being bridged by sulfate ions.
Studies are also recorded for the ammonium/trivalent rare earth double
sulfate tetrahydrate salts,
(NH4)Ln(SO4)2.4H2O,
for the (hitherto) extremal members Ln = La, Tb, which are isomorphous
with the previously studied Ln = Sm monoclinic P
21/c, Z = 4 array,
a ≈ 6·6, b ≈ 19,
c ≈ 8·8 Å, β 97°;
R 0·035, 0·037 for
No 3631, 3337. The array is a
two-dimensional polymer, parallel to the ac plane.
Crystal Structure of Diethylammonium p-Aminobenzoate (Nevanide)
Authors: Smith Graham , Kennard Colin H. L. , Byriel Karl A.
Published: December 2005

The crystal structure of Nevanide (diethylammonium
p-aminobenzoate) has been determined and refined to a
residual R 0·055 for 2797 observed reflections.
Crystals are monoclinic, space group C
2/c, with 32 ion pairs in a cell with dimensions
a 29·510(6), b
17·150(1), c 20·473(5) Å, β
115·153(9)°. The structure is made up of a network of
hydrogen-bonded ions; in this network the 4-aminobenzoate anions form a
primary cyclic tetramer unit in which the amine groups of two residues are
linked tail to tail through hydrogen bonds to single carboxylate oxygens of
the other two residues. All oxygens are then linked peripherally to layers of
diethylammonium cations by strong hydrogen bonding, with all possible hydrogen
bonding sites utilized, giving a three-dimensional network array.
β-Acarbose. VIII.The Synthesis of Some N-Linked Carba-Oligosaccharides
Authors: Tilbrook Matthew G. , Stick Robert V. , Williams Spencer J.
Published: December 2005

Two carbohydrate triflates have been used to alkylate a 1-epivalienamine
derivative to give small amounts of the desired secondary amines, in addition
to amounts of the products of elimination. Deprotection of the secondary
amines afforded a carba-disaccharide and a carba-tetrasaccharide which have
been shown to be good inhibitors of
β-glucosidases.
2-Methoxypsoromic Acid, a New Lichen Depsidone from Pertusaria and Sulcaria Species
Authors: Elix John A. , Wardlaw Judith H. , Obermayer Walter , Archer Alan W.
Published: December 2005

The depsidone 2-methoxypsoromic acid
(4-formyl-3-hydroxy-2,8-dimethoxy-1,9-dimethyl-11-oxo-11
H-
dibenzo[b,e][1,4]dioxepin-6-carboxylic
acid) (9) has been identified in several lichen species. The structure of
compound (9) followed from a combination of spectroscopic
data.
Studies in the Cycloproparene Series: Oxygen Transfer to 1-Diphenylmethylidene- 1 H-cyclopropabenzene
Authors: Bickers Peter T. , Halton Brian , Kay Andrew J. , Northcote Peter T.
Published: December 2005

Oxygen transfer from dimethyldioxiran to 1-diphenylmethylidene-1
H-cyclopropabenzene (8b) proceeds to give the
corresponding epoxy derivative (7b), the simplest and most stable
oxaspiropentene yet recorded. The compound has been characterized
spectroscopically prior to ring expansion and rearrangement to the
cyclobutenone (9b) above 20°C; this is the sole product isolated when the
reaction is performed at or above room temperature. If the oxygenation
reaction is performed under conditions other than strictly anhydrous, the
rearrangement (7b) → (9b) competes with protonation of the oxygen atom
and sequential opening of the three-membered ring to provide the
hydroxyethanone (11b) via the diol (10b).
Reaction of Bromonaphthofurans with Bis(pinacolato)diboron.
Authors: Brimble Margaret A. , Issa Fatiah
Published: December 2005

The synthesis of a dimeric pyranonaphthoquinone (8) was investigated focusing
on a late-stage biaryl coupling of suitably functionalized bromonaphthofurans
by using Suzuki–Miyaura methodology. Bromonaphthofuran (16) underwent
reaction with bis(pinacolato)diboron in the presence of
PdCl2(dppf) to afford boronate ester (21) and
furonaphthofuran (22). ‘In situ’coupling of
the boronate ester (21) with aryl bromide (16) to the desired dimer (11) was
not realized. Bromonaphthofuran (17), prepared by
Diels–Alder/retro-Claisen reaction of bromonaphthoquinone (24) with
diene (25), underwent Suzuki–Miyaura coupling to naphthofuran (27) and
boronate ester (28). Numerous attempts to alter the reaction conditions to
effect homocoupling of bromide (17) to biaryl (19) were unsuccessful.
Bromopyranonaphthoquinone (18) prepared by oxidative rearrangement of (17)
failed to undergo Suzuki–Miyaura coupling.
Pigments of Fungi. LV. The Absolute Configuration of Dermocanarin 4 and the Structure and Stereochemistry of the Dermocanarins 5, 6, 8 and 9 from Australian Toadstools Belonging to the Genus Cortinarius
Authors: Elsworth Catherine , Gill Melvyn , Milanovic Nives M.
Published: December 2005

The stereochemistry in the dihydroanthracenone ring of dermocanarin 4 (1) is
defined as (S) by incorporation of the gentiobioside (2)
of (S)-[6-OMe-
13 C]torosachrysone into the dihydroanthracenone
ring of dermocanarin 4 by fruiting bodies of
Cortinarius sinapicolor. In addition, the new
dermocanarins 5 (3), 6 (4), 8 (5) and 9 (6) are isolated from two other
indigenous toadstools belonging to Cortinarius and their
structure and stereochemistry are deduced from the respective spectroscopic
data and by comparison with dermocanarin 4 (1).
Pigments of Fungi. LVII. Structure and X-Ray Crystallographic Analysis of Dermocanarin 10, a New Naphthalene - Dihydroanthracenone Dimer from an Australian Dermocybe Toadstool
Authors: Gill Melvyn , Millar Petra M. , Raudies Evelin , Phonh-Axa Somphone , White Jonathan M. , Yu Jin
Published: December 2005

The structure and absolute stereochemistry of the fungal metabolite
dermocanarin 10 (2), which differs from all previous members of the
dermocanarin group by virtue of the connectivity between the anthraquinone and
dimethoxynaphthol rings, is deduced from spectroscopic data and confirmed by a
single-crystal X-ray structure analysis.
William Roy Jackson, FRACI, FAATSE, FAIE
Authors: Perlmutter Patrick
Published: December 2005

… first Sir John Monash Distinguished Professor …
Predicting microbial species richness
Authors: Hong Sun-Hee , Bunge John , Jeon Sun-Ok , Epstein Slava S.
Published: December 2005

Microorganisms are spectacularly diverse phylogenetically, but available estimates of their species richness are vague and problematic. For example, for comparable environments, the estimated numbers of species range from a few dozen or hundreds to tens of thousands and even half a million. Such estimates provide no baseline information on either local or global microbial species richness. We argue that this uncertainty is due in large part to the way statistical tools are used, if not indeed misused, in biodiversity research. Here we develop a powerful synthetic statistical approach to quantify biodiversity. It provides statistically sound estimates of microbial richness at any level of taxonomic hierarchy. We apply this approach to a large original 16S rRNA dataset on marine bacterial diversity and show that the number of bacterial species in a sample from marine sediments is (2.4 ± 0.5 SE) × 103. We argue that our methodology provides estimates of microbial richness that are reliable and general, have biologically meaningful SEs, and meet other fundamental statistical standards. This approach can be an essential tool in biodiversity research, and the estimates of microbial richness presented here can serve as a baseline in microbial diversity studies.
A general binding mechanism for all human sulfatases by the formylglycine-generating enzyme
Authors: Roeser Dirk , Preusser-Kunze Andrea , Schmidt Bernhard , Gasow Kathrin , Wittmann Julia G. , Dierks Thomas , von Figura Kurt , Rudolph Markus Georg
Published: December 2005

The formylglycine (FGly)-generating enzyme (FGE) uses molecular oxygen to oxidize a conserved cysteine residue in all eukaryotic sulfatases to the catalytically active FGly. Sulfatases degrade and remodel sulfate esters, and inactivity of FGE results in multiple sulfatase deficiency, a fatal disease. The previously determined FGE crystal structure revealed two crucial cysteine residues in the active site, one of which was thought to be implicated in substrate binding. The other cysteine residue partakes in a novel oxygenase mechanism that does not rely on any cofactors. Here, we present crystal structures of the individual FGE cysteine mutants and employ chemical probing of wild-type FGE, which defined the cysteines to differ strongly in their reactivity. This striking difference in reactivity is explained by the distinct roles of these cysteine residues in the catalytic mechanism. Hitherto, an enzyme–substrate complex as an essential cornerstone for the structural evaluation of the FGly formation mechanism has remained elusive. We also present two FGE–substrate complexes with pentamer and heptamer peptides that mimic sulfatases. The peptides isolate a small cavity that is a likely binding site for molecular oxygen and could host reactive oxygen intermediates during cysteine oxidation. Importantly, these FGE–peptide complexes directly unveil the molecular bases of FGE substrate binding and specificity. Because of the conserved nature of FGE sequences in other organisms, this binding mechanism is of general validity. Furthermore, several disease-causing mutations in both FGE and sulfatases are explained by this binding mechanism.
No science today—the demise of primary science
Authors: Boyle Bill , Bragg Joanna
Published: December 2005

Much has been written about the standards agenda in relation to primary pupil performance levels on end of key stage tests. A range of policy ‘levers’ such as numeracy and literacy strategies have been utilized to hike the annual cohort percentages towards the government targets. However, whether measurable (by standardized testing at ages 7 and 11) national standards in English and mathematics have risen or not does not justify the unbalancing of the intended ‘broad and balanced’ curriculum (DES, 1988) which has taken place to try to achieve the national percentage targets. The authors find that this compression of the curriculum has not just extended to the foundation subjects but has substantially reduced teaching time in science, supposedly one of the ‘core’ subjects. The curriculum data on which the authors base their findings are supplied by the Qualifications and Curriculum Authority's own longitudinal monitoring of the school curriculum which has been carried out by the authors from 1996 to 2005.
Classification of learning outcomes: evidence from the computer games literature
Authors: O'Neil Harold F. , Wainess Richard , Baker Eva L.
Published: December 2005

Following up on an earlier issue of The Curriculum Journal (Vol. 16, No. 1), this article focuses on learning outcomes in the context of video games. Learning outcomes are viewed from two theoretical frameworks: Kirkpatrick's levels of evaluation and the CRESST model of learning. These are used to analyse the outcomes claimed in journal articles that report empirical work, indicating the usefulness of the frameworks, and the necessity to consider the role of affective learning. The article ends with some comments on the relationship of instructional design to effective games and learning outcomes.
Debating debating: a reflection on the place of debate within secondary schools
Authors: Jerome Lee , Algarra Bhavini
Published: December 2005

This article is based on the authors' reflections on observations and interviews with students and staff involved in a debate competition in London secondary schools. Taking the data we collected as our starting point, we seek to draw on research from a range of perspectives, including political education, political philosophy and debate as a teaching method, to clarify the role of debate within a pedagogy for democracy. We consider the case for promoting debate in general terms, and then go on to discuss the role and form debate should take in such a pedagogy. Here we contrast models based on adversarial and deliberative democracy and consider the need for teachers to be aware of the benefits and shortcomings of each. We then draw on the concept of students' public voice to discuss some of the issues that need to be borne in mind when developing these strategies in class. Finally we pose a number of questions for future investigation, which may help teachers reflect on their own practice as well as inform our own ongoing research in this area.
Curriculum studies in initial teacher education: the importance of holism and project 2061
Authors: Clark John
Published: December 2005

Initial teacher education programmes, in order to comply with the requirements for teacher registration, are usually expected to introduce student teachers to the mandated curriculum. Often this is done uncritically, so students tend to accept rather than examine the underlying epistemological model which partitions knowledge into distinct ‘pillars of wisdom’. But there is little agreement over how knowledge is to be partitioned, which raises the question of if it can be partitioned at all. A different philosophical model—holism—is proposed based on the metaphor of a spider's web, and the Queensland ‘New Basics’ project is given as an example which fits this alternative approach. A second problem is in the overcrowding of the curriculum and here Project 2061 offers a set of robust criteria for making rational decisions about curriculum content.
Dynamical Morphology of the Brain′s Ventricular Cavities in Hydrocephalus
Authors: Drapaca C. S. , Sivaloganathan S. , Tenti G. , Drake J. M.
Published: December 2005

Although interest in the biomechanics of the brain goes back over centuries, mathematical models of hydrocephalus and other brain abnormalities are still in their infancy and a much more recent phenomenon. This is rather surprising, since hydrocephalus is still an endemic condition in the pediatric population with an incidence of approximately 1–3 per 1000 births. Treatment has dramatically improved over the last three decades, thanks to the introduction of cerebrospinal fluid (CSF) shunts. Their use, however, is not without problems and the shunt failure at two years remains unacceptably high at 50%. The most common factor causing shunt failure is obstruction, especially of the proximal catheters. There is currently no agreement among neurosurgeons as to the optimal catheter tip position; however, common sense suggests that the lowest risk location is the place that remains larger after ventricular decompression drainage. Thus, success in this direction will depend on the development of a quantitative theory capable of predicting the ultimate shape of the ventricular wall. In this paper, we report on some recent progress towards the solution to this problem.
The Solution of Inverse Non‐Linear Elasticity Problems That Arise When Locating Breast Tumours
Authors: Whiteley Jonathan P.
Published: December 2005

Non‐linear elasticity theory may be used to calculate the coordinates of a deformed body when the coordinates of the undeformed, stress‐free body are known. In some situations, such as one of the steps in the location of tumours in a breast, the coordinates of the deformed body are known and the coordinates of the undeformed body are to be calculated, i.e. we require the solution of the inverse problem. Other than for situations where classical linear elasticity theory may be applied, the simple approach for solving the inverse problem of reversing the direction of gravity and modelling the deformed body as an undeformed body does not give the correct solution. In this study, we derive equations that may be used to solve inverse problems. The solution of these equations may be used for a wide range of inverse problems in non‐linear elasticity.
A Numerical Investigation of Heat Transfer Cardiac Output Measurements
Authors: Fotheringham P. , Gourlay A. R. , Mckee S. , Andrews S.
Published: December 2005

Measurement of cardiac output is often investigated using a technique based on hot‐film anemometry. Here, we discuss a modification to hot‐film anemometry, which involves a cylindrical heating element mounted flush on the surface of a typical Swan‐Ganz catheter. In contrast to traditional thermodilution, the method discussed here has the potential to allow continuous monitoring of cardiac output.

This paper demonstrates that there is a simple approximate relationship between the power input to the device to maintain a temperature of one degree above blood heat and cardiac output. Since, the heat transfer and the fluid flow decouple, a numerical model of the heat transfer of a cylindrical catheter (with heating element) sitting concentrically within a rigid cylindrical artery is developed. Numerical results were obtained for a wide selection of flow profiles, including experimental data. The results indicate that the cardiac output/power input relationship is extremely robust with respect to flow profile and system parameter variation.
Development of a Species‐Specific Model of Cerebral Hemodynamics
Authors: Daun Silvia , Tjardes Thorsten
Published: December 2005

In this paper, a mathematical model for the description of cerebral hemodynamics is developed. This model is able to simulate the regulation mechanisms working on the small cerebral arteries and arterioles, and thus to adapt dynamically the blood flow in brain. Special interest is laid on the release of catecholamines and their effect on heart frequency, cardiac output and blood pressure. Therefore, this model is able to describe situations of severe head injuries in a very realistic way.
Dismissal, Expulsion, and Emigration of German-Speaking Economists after 1933
Authors: Hagemann Harald
Published: December 2005

The dismissal of academicians from German universities under the Restoration of Civil Service Act (Gesetz zur Wiederherstellung des Berufsbeamtentums), promulgated by the National Socialists on April 7, 1933, and the expulsion of academicians from Germany, Austria, and other European countries interrupted or destroyed promising developments in economics, as well as in physics or other areas. According to this new “law,” which was passed by the Nazis in a short cut immediately after coming to power, “disagreeable” persons could be dislocated from the public service predominantly for racist (section 3) or political (section 4) reasons.
Reflections of a “Second Generation” German Emigré: The Impact of my Emigré Professors on a Future Economist
Authors: Rima Ingrid H.
Published: December 2005

My reflections are at least partly those of the child of an emigré who grew up to beome an economist. Since my father was an engineer from Germany's Barmen-Elberfeld textile city—also the city of Friedrich Engels—he clearly is not among the first generation of German scholars who were deprived of their professional positions as the Hitler regime came into power. Indeed, somewhat like Joseph Schumpeter, he came to America to grasp an opportunity rather than to avoid a threat. Like many of educated men of his generation, he was fluent in five languages and an ardent student of philosophy, history, and political economy. His move to America, after three or four trial visits, preceded my birth, because in those days before international air travel the seven day ocean voyage between Bremerhaven and New York was so daunting for a woman approaching childbirth that I was close to a year old before our arrival in America. My early childhood was uneventful except for the arrival of two siblings, and the only negative I recall from those early days was that I hated my first name, Ingrid (so carefully chosen by my parents), and longed to be called Jane, Anne or anything other than Ingrid.
Comments on Papers on Emigré Economists
Authors: Samuels Warren J.
Published: December 2005

Historians of economic thought, as well as the emigré subjects themselves, are profoundly indebted to Harald Hagemann and Claus-Dieter Krohn for their efforts in documenting the phenomena of German-speaking emigré economists.
On Coherent Sets and the Transmission of Confirmation*
Authors: Dietrich Franz , Moretti Luca
Published: December 2005

In this paper, we identify a new and mathematically well-defined sense in which the coherence of a set of hypotheses can be truth-conducive. Our focus is not, as usual, on the probability, but rather on the confirmation of a coherent set and its members. We show that if evidence confirms a hypothesis, confirmation is ‘transmitted’ to any hypotheses that are sufficiently coherent with the former hypothesis, according to some appropriate probabilistic coherence measure such as Olsson's or Fitelson's measure. Our findings have implications for scientific methodology, as they provide a formal rationale for the method of indirect confirmation and the method of confirming theories by confirming their parts.