bluuebunny/crossref_metadata_2025 huggingface dataset:
An empirical approach to the bond additivity model in quantitative interpretation of sum frequency generation vibrational spectra
Authors: Wu Hui , Zhang Wen-kai , Gan Wei , Cui Zhi-feng , Wang Hong-fei
Published: October 2006

Knowledge of the ratios between different polarizability βi′j′k′ tensor elements of a chemical group in a molecule is crucial for quantitative interpretation and polarization analysis of its sum frequency generation vibrational spectroscopy (SFG-VS) spectrum at interface. The bond additivity model (BAM) or the hyperpolarizability derivative model along with experimentally obtained Raman depolarization ratios has been widely used to obtain such tensor ratios for the CH3, CH2, and CH groups. Successfully, such treatment can quantitatively reproduce the intensity polarization dependence in SFG-VS spectra for the symmetric (SS) and asymmetric (AS) stretching modes of CH3 and CH2 groups, respectively. However, the relative intensities between the SS and AS modes usually do not agree with each other within this model even for some of the simplest molecular systems, such as the air/methanol interface. This fact certainly has cast uncertainties on the effectiveness and conclusions based on the BAM. One of such examples is that the AS mode of CH3 group has never been observed in SFG-VS spectra from the air/methanol interface, while this AS mode is usually very strong for SFG-VS spectra from the air/ethanol interface, other short chain alcohol, as well as long chain surfactants. In order to answer these questions, an empirical approach from known Raman and IR spectra is used to make corrections to the BAM. With the corrected ratios between the βi′j′k′ tensor elements of the SS and AS modes, all features in the SFG-VS spectra of the air/methanol and air/ethanol interfaces can be quantitatively interpreted. This empirical approach not only provides new understandings of the effectiveness and limitations of the bond additivity model but also provides a practical way for its application in SFG-VS studies of molecular interfaces.
On low-temperature polyamorphous transformations
Authors: Bakai A. S.
Published: October 2006

A theory of polyamorphous transformations in glasses is constructed in the framework of a model of heterophase fluctuations with allowance for the fact that a glass inherits the short- and intermediate-range order from the liquid. A multicomponent order parameter describing the concentration of fluctuons with different types of short-range order is introduced, along with the concepts of isoconfigurational and non-isoconfigurational transitions in the glass. Taking the nonergodicity, nonequilibrium, and multiplicity of structural states of a glass into account leads to a kinetic criterion of observability of polyamorphism of a glass. As an example, a theory is constructed for the low-temperature first-order phase transition in an orientational glass based on doped fullerite. The relaxation processes of this system are described, including the subsystem of tunneling states. The possibility of a hierarchy of polyamorphous transformations in a glass is discussed.
Stability of the charged surface of a liquid dielectric
Authors: Kushnir L. , Shikin V.
Published: October 2006

A theory is proposed for the onset of instability of the interface between two liquid dielectrics in the presence of an external electric field normal to that interface. The details of the critical conditions of instability are investigated as functions of the external parameters of the problem: the ratio ε=ε1∕ε2 of the dielectric constants ε1 and ε2 of the two media, the thickness of the liquid films found in contact, etc. In particular, a quantitative difference in the structure of the corrugation of the liquid interface is noted for different ε. In the case of finite values of ε the critical value of the corrugation period remains finite. However, if ε→0 (which corresponds to an infinite conductivity of one of the media) the corrugation period also grows without bound. The possibility of reconstruction of the liquid interface under supercritical conditions is demonstrated (the appearance of mechanically equilibrium corrugation of the liquid interface with a corrugation amplitude that depends on the degree of supercriticality, i.e., the excess of the electric field above the critical value). The existence of two regimes of reconstruction is pointed out: “soft” and “hard,” which are realized under definite relationships among the external parameters of the problem. The details are discussed for the “soft” reconstruction, where the formalism used has an actual domain of applicability. It is noted that manipulations with the parameter ε=ε1∕ε2 in the problem under discussion are qualitatively equivalent to variation of the degree of occupation δ of the surface of the cryogenic liquid by charged particles (electrons or ions) from its zero value (the case of a charge-free liquid surface) up to its maximum value δ=1, when the general problem gives answers that are characteristic for the development of instability of the free interface of a metallic liquid.
Electric-field-induced low temperature oxidation of tungsten nanowires
Authors: Nowak C. , Kirchheim R. , Schmitz G.
Published: October 2006

Experiments on the room temperature oxidation of tip-shaped tungsten nanowires under an externally applied electric field are reported, yielding the controlled formation of tungsten oxide layers up to several tens of nanometers thick in the high field region at the tip of the nanowires. The initially very fast oxidation reaction is observed to virtually terminate at a field dependent state, defined by a critical field strength of 1.15(2)×109V∕m. Since electric fields of the order of 109V∕m are easily obtained, the observed effect may influence the chemical stability of nanoscaled systems significantly when used in ambient atmosphere.
Transmission of light by a single subwavelength cylindrical hole in metallic films
Authors: Bai Ming , García N.
Published: October 2006

This letter presents theory and finite-difference time-domain calculations in excellent agreement with experiments for the transmission of a single subwavelength cylindrical hole in Ag metallic films. The authors discuss the very large enhancement in transmission by single holes in terms of surface plasmons at the interface of the hole. These are similar to the surface plasmons in metallic cylinders reported by Economou and co-workers [Phys. Rev. B 10, 3038 (1974); 24, 6908 (1981)]. The peak structures observed in experiments with arrays of holes are a consequence of interference of the beams transmitted by each hole and are determined by the hole periodicities. The role of the arrays in enhancement of the transmission due to surface plasmon polaritons appears to be marginal.
Experiment and first principles investigation on the hydrogen-hindered phase transition of ferroelectric ceramics
Authors: Huang H. Y. , Chu W. Y. , Su Y. J. , Li J. X. , Qiao L. J. , Shi S. Q.
Published: October 2006

In this letter, hydrogen-hindered phase transition of ferroelectric ceramics from cubic to tetragonal has been studied by experiment and first principles calculation. The calculation shows that for hydrogenated tetragonal PbTiO3, double-lowest-energy sites of Ti along the c axis exist no longer and the only lowest energy site locates at the center of the cell. The calculation can explain the experiment that hydrogen charged above its Curie temperature can hinder phase transition of lead zirconate titanate from cubic paraelectricity to tetragonal ferroelectricity.
Hybrid Fabry-Pérot étalon using an electro-optic polymer for optical modulation
Authors: Gan Haiyong , Zhang Hongxi , DeRose Christopher T. , Norwood Robert A. , Fallahi Mahmoud , Luo Jingdong , Jen Alex K.-Y. , Liu Boyang , Ho Seng-Tiong , Peyghambarian Nasser
Published: October 2006

The authors present a Fabry-Pérot étalon using an electro-optic (EO) polymer material as the nonlinear medium. The two electrodes used to apply voltage across the EO polymer include an indium tin oxide electrode outside the étalon cavity and a low-absorption indium oxide electrode inside the étalon cavity. High finesse (∼234) and a low insertion loss (∼4dB) have been obtained. An isolation ratio of 10dB and ∼10% modulation depth at 200kHz with 5V applied voltage have been achieved. These results indicate that EO polymer étalons are promising as spatial light modulators for information technology.
The Time Course of Visual Afterimages: Data and Theory
Authors: Wede Joshua , Francis Gregory
Published: October 2006

Sequential viewing of two orthogonally related patterns produces an afterimage of the first pattern (Vidyasagar et al, 1999 Nature399 422 – 423; Francis and Rothmayer, 2003 Perception & Psychophysics65 508 – 522). We investigated how the timing between the first stimulus (a vertical bar grating) and the second stimulus (a horizontal bar grating) affected the visibility of the afterimage (a perceived vertical grating). As the duration from offset of the first stimulus increased, reports of afterimages decreased. Holding fixed the total time from offset of the first stimulus and increasing the duration from offset of the second stimulus while decreasing the time between the first and second stimuli, caused a decrease in afterimage reports. We interpret this finding in terms of Grossberg's BCS – FCS (boundary contour system – feature contour system) theory. In this theory, the afterimage percept is the result of color complement after-responses in the FCS system interacting with orientation after-responses in the BCS system. The two types of after-responses interact at a stage of neural filling-in to produce the afterimage percept. As the duration between the stimuli increases, the color after-responses weaken so that visible filling-in is less likely to occur. A similar effect occurs for the orientation after-responses but at a faster time scale. Simulations of the model match the experimental data.
The chloro and bromo complexes of iridium(III) and iridium(IV). I. Preparation
Authors: Fergusson JE , Rankin DA
Published: October 2006

The chloro
and bromo salts A2 [IrX6] (A = K, NH4, Rb, Cs; X = Cl, Br), A3 [IrCl6].H2O
(A = K, NH4, Rb, Cs), A3 [IrCl6]
(A = K, NH4), A2 [IrCl5H2O] (A = Rb, CS), (H3O)K8- [IrBr6]3.9H2O,
A3 [IrBr6].H2O (A = NH4, Rb, CS), A3 [Ir2C19] (A = Rb, CS), A3 [Ir2Br9] (A = Rb, Cs, Me4N) and [Co(NH3)6]
[IrX6] (X = Cl, Br) have been prepared and the various reaction
paths studied. The ready oxidation of IrIII to IrIV
and the equilibrium between IrIII monoiridium
and diiridium bromo species means many reactions give
a mixture of complexes.
Lewis-base adducts of Group 1B metal(I) compounds. VI. Crystal structure of the 1 : 2 adduct of copper(I) iodide with pyridine
Authors: Dyason JC , Engelhardt LM , Healy PC , White AH
Published: October 2006

Copper(I) iodide on recrystallization from neat pyridine yields a 1 : 2 adduct;
it is established by single-crystal X-ray diffraction methods at 295 K that
this is a ��'-diiodobridged dimer,
with four- coordinate copper(I), [(py)2CuI2Cu(py)2]. Crystals are orthorhombic, C2221,
a 14.578(4), b 10.448(3), c 31.559(7) �,
Z = 8 dimers. Cu. . .Cu is 2.699(5) �.
Molybdenum(VI) complexes of Schiff bases derived from salicylaldehyde and 2-aminoethanethiol (cysteamine)
Authors: Goh W , Lim M
Published: October 2006

The reaction of
salicylaldehyde and 2-aminoethanethiol (cysteamine) in methanol results in two
distinct products: a yellow oil, 2-(2-mercaptoethyliminomethyl)phenol, and a
yellow crystalline solid,
2,2'-[dithiobis(ethane-1,2-diyl)bis(nitrilomethylidyne)]bisphenol, which is an
oxidation product of the former. The latter compound may also be prepared from
salicylaldehyde and 2,2'-dithio-bis(ethylamine) (cystamine) in methanol.
2-(2''-Mercaptoethyliminomethyl)phenol reacts with MoO2(acac)2
(acac = pentane-2,4-dionate) in methanol to yield a red crystalline solid with
empirical formula MoO2(mep) [mep = 2-(2"-
mercaptoethyliminomethyl)phenolate]. This red solid exists as a dimer in the
solid state. It forms adducts with dimethyl sulfoxide, hexamethylphosphoric
acid triamide and pyridine.
2,2'-[Dithiobis(ethane-1,2-diyl)bis(nitrilomethylidyne)]bisphenol reacts with MoO2(acac)2
to yield a pale yellow solid. It is a monomeric compound whose formula is MoO2(dbp)
{dbp = 2,2'- [dithiobis(ethane-1,2-diyl)bis(nitrilomethylidyne)]bisphenolate}.
It does not form an adduct and is decomposed by an excess of
tetramethylammonium hydroxide in methanol.
Potential Antimalarials. XV. Di-Mannich Bases of 2-(7'-Chloroquinolin-4'-ylamino)phenol and 2-[7'-Bromo( and trifluoromethyl)-1',5'-naphthyridin-4'-ylamino]phenol
Authors: Barlin GB , Nguyen TMT , Kotecka B , Rieckmann KH
Published: October 2006

A total of 26 di-Mannich base derivatives of 2-(7'-chloroquinolin-4'-ylamino)phenol and 2-[7'- bromo (and trifluoromethyl )-1',5'-naphthyridin-4'-ylino]phenol, such as 2-(7'-chloroquinolin- 4'-ylamino)-4,6-bis( piperidin-1″-ylmethyl )phenol, together with some 3- and 5-methyl derivatives and mono-Mannich analogues, have been prepared by condensation of the 4-chloro heterocycle with the appropriate Mannich base derivatives of 2-aminophenols. In in vitro tests against Plasmodium falciparum, many of the di-Mannich base derivatives of 2-(7'-chloroquinolin-4'-ylarnino)phenol exhibited activity comparable to or superior to chloroquine against the chloroquine -sensitive (FCQ-27) isolate, and vastly superior activity compared with chloroquine against the chloroquine -resistant (K-1) isolate. Strong antimalarial activity was also revealed in in vivo tests against Plasmodium vinckei vinckei in mice.
Structural Studies of Seven Compounds of Cobalt(III) With trans-6,13-Diamino-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane
Authors: Curtis NF , Robinson WT , Weatherburn DC
Published: October 2006

The structures of seven compounds of trans-6,13-diamino-6,13-dimethyl-1,4,8,11-tetraacyclotetradecane
(diam) with cobalt(III) have been determined by X-ray diffractometry: (1),
trans-α-[{Co(diam-N5)}2(O2)](ClO4)4.2H2O (monoclinic, P21/n, a 10.673(2), b 22.924(8),
c 19.332(5) Ǻ,β 114 19(2)°, R 0.044 for 4547reflections); (2), trans-α-[Co(diam-N5)Cl](ClO4)2
(orthorhombic, P 212121, a 9.043(4), b 11.214(4), c 21.431(8) A, R 0.055 for 1541 reflections);
(3), trans-α- Co(diamH-N5)Cl] [ZnCl4] Cl.H2O (orthorhombic, Pna 21, a 25.26(5), b 9.866(2),
c 9.457(2) 1, R 0.108 for 1686 reflections); (4), trans-α-[Co(diamH-N5)(H2O)Cl3.ClO4
(monoclinic, P 21/n, a 12.928(8), b 8.554(5), c 20.624(12) A, β 106.00(4)°, R 0.060
for 2094 reflections); (5), trans-γ-[Co(diamH-N5)Cl]Cl3.3H2O (orthorhombic, P212121, a
12.895(7), b 12.898(9), c 13 -417(4) Ǻ, R 0.062 for 860 reflections); (6), trans-β-[Co(diamHN5)
Cl] [ZnCl4]CI.½H2O.½C3.H7OH(triclinic, P1, a 10.469(4), b 9.167(5), c 15.464(6) Ǻ, α
73.74(4), β 71.15(3), γ 73.70(1)°, R 0.045 for 3685 reflections); (7), trans-β-[Co(diamH2-
N4)Cl2] [ZnCl4]Cl.½H2O.½C2.H5OH(triclinic, P1, a 10.138(2), b 12.011(3), c 12-451(2) Ǻ,
α 79,87(2), β 66.64(1), γ 66.64(1)°, R 0.035 for 2637 reflections). The cations of compounds (1)-(6) all have pentadentate diam (diam-N5 or diamH-N5) with one primary amino substituent coordinated trans to the additional ligand. Compounds (1)-(4) have the pentadentate macrocycle in cyclam configuration (1). R,S,R,S, with all four secondary amine groups on the same side of the molecular plane, with one six-membered chelate ring in a boat conformation with the amino substituent coordinated, and the other in a chair conformation. Compound (5) has the pentadentate macrocycle in configuration (2), R,R,S,R, with one NH group alone on one side of the molecular plane with the six-membered chelate ring with the non-coordinated amrnonio substituent in a skew conformation. Compounds (6) and (7) have the R,R,S,S configuration (S'), (6) having diamH-N5 with one amine substituent coordinated, and (7) with planar tetradentate diamH2-N4 in the macrocycle conformation usual for planar coordinated cyclam compounds, the ammonio substituents being equatorially oriented.
Metal Ion Cages: Capping Reactions With Bifunctional Methylene Compounds and Formaldehyde
Authors: Geue RJ , Petri WR , Sargeson AM , Snow MR
Published: October 2006

[(1,1,1-Tris(4-amino-2-azabutyl)ethane)cobalt(III)](3+) ([co(sen)]3+) and [(tris(4-amino-2- azabutyl)amine)cobalt(III)](3+) ([Co(azasen)]3+) react with formaldehyde and diethyl malonate or cyanoacetic acid ethyl ester in the presence of base to form macrobicyclic cages [ox- osarcophagine (oxosar) and oxoazasarcophagine (azaoxosar)] about the metal ion. The cage structure of the complexes has been established by an X-ray crystallographic analysis of [(1-carboxy-8-methyl-2-oxo-3,6,10,13, 16,19-hexaazabicyclo[6.6.6]icosanato)cobalt(III)] diperchlorate [Co(Me,CO2H-oxosar- H)]2+ which crystallizes in the orthorhombic space group Pbcn, with cell parameters a 33.61, b 10.42, c 13.743 � , and V 4813 � 3 , and Z 8. The chiral cobalt(III) complex is characteristically inert to substitution and racemization, but the cobalt(II) complex, obtained by reduction of the appropriate cobalt(III) compound, is surprisingly stable both to loss of Co2+ ion and to racemization at 25°C (pH 7.1, t½4.5 days). The syntheses, spectroscopic and chemical properties are reported. The kinetics of the electron self exchange for the cage system [Co(Me,CO2Et-oxosar-H)]+/2+, and of H2O2 formation from [coII(Me,co2Et-oxosar - H)]+ and O2 are reported. Similar syntheses have been carried out to half-cap the [co(en)3]3+ ion (en = ethane-1,2-diamine). These and related reactions have allowed substituents such as COOR, COOH, CN, COCl, CONR2, NH2 and NO2 to be placed on the bridgehead carbon atoms, and have altered the redox potentials of the systems by at least 0.3 V. The oxosar COII ions are useful as powerful reducing agents [from c. -0.3 to -0.6 V (v. n.h.e.)], and the cages are capable of further derivatization to build larger macromolecules.
Short- and long-term demographic changes in house mouse populations after control in dryland farming systems in Australia
Authors: Brown Peter R.
Published: October 2006

In Australia, outbreaks of house mice (Mus domesticus) cause significant damage to agricultural crops. Rodenticides are used to reduce damage to crops, but the demographic consequences of applying rodenticides are poorly understood. Furthermore, it is not known whether the reduction induced by rodenticides would be similar to that of a natural crash in abundance at the end of mouse outbreaks. I compared the demographic responses of populations of mice to broad-scale field application of fast-acting, acute rodenticides (strychnine and zinc phosphide) in three grain-growing regions of Australia on baited and unbaited sites through live-trapping of mouse populations before baiting and up to four months after baiting. The reductions in population density in each region immediately after baiting were <40%, 92% and 98%. There were few consistent changes in demographic responses across the three regions for bodyweight (no change, increased or decreased), proportion of juveniles (increased or decreased), sex ratio (no change or bias towards females), survival (no change or decreased) and relative body condition (no change or increased). The differences in demographic responses appeared to be related to differences in the efficacy of the rodenticide. A natural crash in densities occurred over a 2–4-week period after baiting and induced a >85% decline in population densities across all regions on baited and unbaited sites. The natural crash caused increases and decreases in bodyweights, a reduction in the proportion of juveniles, male bias, poor survival and poor relative body condition. Poor survival was the only demographic parameter that was consistent for baiting and the natural crash. Five of seven demographic responses for mice during the natural crash were similar to those found in the literature for the decline phase of cyclic vole and lemming populations in the Northern Hemisphere. These results raise the question of whether mouse populations should be baited if a natural crash would occur anyway, but the timing of the natural crash is always uncertain and rodenticides are inexpensive.
Movements of frugivorous birds among fragmented rainforests in the Northern Territory, Australia
Authors: Price Owen F.
Published: October 2006

Rainforests in the Northern Territory occur as small patches, and the frugivorous birds that depend on them are thought to move among the patches. I attached radio-transmitters to 41 birds of four species captured in several locations near Darwin. I recorded 55 interpatch flights, and estimated flight rates as between once per day and five days for figbirds and pied imperial-pigeons. The flight rates for rose-crowned fruit-doves and yellow orioles were much lower, but no reliable estimate could be made. The median flight distance was 2.5 km but one in five flights were more than 10 km. In addition, one pigeon flew 220 km in preparation for migration from Australia. Birds often undertook exploratory flights, returning to the original patch. Birds of one species captured together usually flew to different locations. When birds left a patch, it was usually to a distant patch, rather than a near neighbour. These movement patterns demonstrate that frugivorous birds use the rainforest network in a complex way. The birds depend on a network of rainforest patches and the pigeons and figbirds probably disperse large quantities of seeds among the patches. The conservation of rainforest ecosystems in northern Australia will depend on the protection of the current configuration of patches rather than a representative set of patches.
The omega-3 fatty acid docosahexaenoate attenuates endothelial cyclooxygenase-2 induction through both NADP(H) oxidase and PKCε inhibition
Authors: Massaro Marika , Habib Aida , Lubrano Laura , Turco Serena Del , Lazzerini Guido , Bourcier Todd , Weksler Babette B. , De Caterina Raffaele
Published: October 2006

A high intake of the omega-3 fatty acid docosahexaenoate [docosahexaenoic acid (DHA)] has been associated with systemic antiinflammatory effects and cardiovascular protection. Cyclooxygenase (COX)-2 is responsible for the overproduction of prostaglandins (PG) at inflammatory sites, and its expression is increased in atheroma. We studied the effects of DHA on COX-2 expression and activity in human saphenous vein endothelial cells challenged with proinflammatory stimuli. A ≥24-h exposure to DHA reduced COX-2 expression and activity induced by IL-1, without affecting COX-1 expression. DHA effect depended on the NF-κB-binding site in the COX-2 promoter. EMSAs confirmed that DHA attenuated NF-κB activation. Because MAPK, PKC, and NAD(P)H oxidase all participate in IL-1-mediated COX-2 expression, we also tested whether these enzymes were involved in DHA effects. Western blots showed that DHA blocked nuclear p65 NF-κB subunit translocation by decreasing cytokine-stimulated reactive oxygen species and ERK1/2 activation by effects on both NAD(P)H oxidase and PKCε activities. Finally, to address the question whether DHA itself or DHA-derived products were responsible for these effects, we inhibited the most important enzymes involved in polyunsaturated fatty acid metabolism, showing that 15-lipoxygenase-1 products mediate part of DHA effects. These studies provide a mechanistic basis for antiinflammatory and possibly plaque-stabilizing effects of DHA
Sungear: interactive visualization and functional analysis of genomic datasets
Authors: Poultney Christopher S. , Gutiérrez Rodrigo A. , Katari Manpreet S. , Gifford Miriam L. , Paley W. Bradford , Coruzzi Gloria M. , Shasha Dennis E.
Published: October 2006

Summary: Sungear is a software system that supports a rapid, visually interactive and biologist-driven comparison of large datasets. The datasets can come from microarray experiments (e.g. genes induced in each experiment), from comparative genomics (e.g. genes present in each genome) or even from non-biological applications (e.g. demographics or baseball statistics). Sungear represents multiple datasets as vertices in a polygon. Each possible intersection among the sets is represented as a circle inside the polygon. The position of the circle is determined by the position of the vertices represented in the intersection and the area of the circle is determined by the number of elements in the intersection. Sungear shows which Gene Ontology terms are over-represented in a subset of circles or anchors. The intuitive Sungear interface has enabled biologists to determine quickly which dataset or groups of datasets play a role in a biological function of interest.

Availability: A live online version of Sungear can be found at

Contact:  shasha@cs.nyu.edu

Supplementary information: Submitted—link TBD.
Oxidation‐Based Model for Thermal Barrier Coating Life
Authors: MILLER ROBERT A.
Published: October 2006

A procedure is described for modeling the lives of thermal barrier coatings subjected to high‐temperature environments. The model is used to calculate cycles‐to‐failure as a function of heating cycle duration. It is based on the presumption that oxidation is the single important time‐dependent factor which limits the life of these coatings, and that oxidation‐induced strains combine with cyclic strains to promote slow crack growth in the ceramic layer. Good agreement is obtained between calculated and experimental lives for specimens tested in a furnace. This shows that an oxidation‐based approach is promising. The importance of reproducible specimen preparation is also discussed.
Theoretical Model of Impact Damage in Structural Ceramics
Authors: LIAW B.M. , KOBAYASHI A.S. , EMERY A.F.
Published: October 2006

This paper presents a mechanistically consistent model of impact damage based on elastic failures due to tensile and shear overloading. An elastic axisymmetric finite element model is used to determine the dynamic stresses generated by a single particle impact. Local failures in a finite element are assumed to occur when the primary/secondary principal stresses or the maximum shear stress reach critical tensile or shear stresses, respectively. The succession of failed elements thus models macrocrack growth. Sliding motions of cracks, which closed during unloading, are resisted by friction and the unrecovered deformation represents the “plastic deformation” reported in the literature. The predicted ring cracks on the contact surface, as well as the cone cracks, median cracks, radial cracks, lateral cracks, and damage‐induced porous zones in the interior of hot‐pressed silicon nitride plates, matched those observed experimentally. The finite element model also predicted the uplifting of the free surface surrounding the impact site.
Vaporization Thermodynamics and Enthalpy of Formation of Aluminum Silicon Carbide
Authors: BEHRENS ROBERT G. , RINEHART GARY H.
Published: October 2006

The vaporization thermodynamics of aluminum silicon carbide was investigated using Knudsen effusion mass spectrometry. Vaporization occurred incongruently to give Al(g), SiC(s), and graphite as reaction products. The vapor pressure of aluminum above (Al4SiC4+ SiC + C) was measured using graphite effusion cells with orifice areas between 1.1 × 10−2and 3.9X10−4 cm2. The vapor pressure of aluminum obtained between 1427 and 1784 K using an effusion cell with the smallest orifice area, 3.9X10−4 cm2, is expressed as

log p (Pa) =−(18567 ± 86) (K/T) + (12.143 ± 0.054)

The third‐law calculation of the enthalpy change for the reaction Al4SiC4(s) = 4Al(g) + SiC(hex) + 3C(s) using the present aluminum pressures gives ΔH°(298.15 K) = (1455 ± 79) kJ·mol−1. The corresponding second‐law result is ΔH°(298.15 K) = (1456 ± 47) kJ·mol−1. The standard enthalpy of formation of Al4SiC4(s) from the elements calculated from the present vaporization enthalpy (third‐law calculation) and the enthalpies of formation of Al(g) and hexagonal SiC is ΔH°f= ‐(221 ± 85) kJ·mol−1. The standard enthalpy of formation of Al4SiC4(s) from its constituent carbides Al4C3(s) and SiC(c, hex) is calculated to be ΔH°(298.15 K) = (38 ± 92) KJ·mol−1.
High‐pressure Self‐Combustion Sintering for Ceramics
Authors: Miyamoto Yoshinari , Koizumi Mitsue , Yamada Osamu
Published: October 2006

The high‐pressure self‐combustion sintering process can be used to synthesize and simultaneously sinter ceramics in a very short time by taking advantage of exothermic reactions under high pressure. A dense TiB2 compact was fabricated in a few seconds by electric ignition on one end of a powdered mixture of Ti and B under 3 GPa.
Electrical Resistivities of Monocrystalline and Polycrystalline TiB2
Authors: McLEOD A. D. , HAGGERTY J. S. , SADOWAY D. R.
Published: October 2006

The electrical resistivity of monocrystalline and polycrystalline TiB2, was measured under an inert atmosphere by a four‐point ac impedance technique over the range 298 to 1373 K. The results are expressed in the form ρ‐ρ298=m(T‐298). The following values of ρ298 (μω.cm) and m(nω.cm‐K‐1) were determined: for polycrystalline TiB2 (69% dense) 18.2 and 95; for polycrystalline TiB2 (99% dense) 7.4 and 42; and for monocrystalline TiB2, 6.6 and 34.9.
Statistically Designed Optimization of a Glass Composition
Authors: CHICK L. A. , PIEPEL G. F.
Published: October 2006

An efficient, statistically based methodology for development and optimization of multicomponent materials is presented. The approach is illustrated with a five‐component nuclear waste glass. A composition field is defined, test compositions are statistically chosen, and their measured property data are used to fit empirical models. These models are then used to predict the optimum composition. The following nuclear waste glass components were investigated: SiO2, B2O3, Na2O, CaO, and simulated nuclear waste. The following properties were modeled: viscosity, chemical durability, and crystallinity. Successful models were constructed by using data from 27 test melts. This methodology could be applied to a wide range of ceramic mixture problems.
Causes and Effects of Fe‐Bearing Inclusions in Sintered Si3N4
Authors: PASTO ARVID E.
Published: October 2006

Iron is shown to increase the tendency for Si3N4 to decompose by formation of stable Fe‐Si alloys. The decomposition reaction is temperature‐ and pressure‐sensitive, with increasing temperatures causing greater reaction. The liquid Fe‐Si alloy produced at elevated temperatures solidifies on cooling and results in metallic inclusions that act as flaws and thus mechanical failure origins.
Crystalline Phase Change in Yttria‐Partially‐Stabilized Zirconia by Low‐Temperature Annealing
Authors: SATO TSUGIO , SHIMADA MASAHIKO
Published: October 2006

Changes in the phase composition and microstructure of yttria‐partially‐stabilized zirconia by low‐temperature annealing were investigated at 100° to 500°C using bodies sintered from coprecipitated fine ZrO2‐Y2O3 powders at varied temperatures. Tetragonal zirconia on the surfaces of bodies sintered at <1500°C transformed to the monoclinic phase at 100° to 400°C. Transformation behavior was strongly affected by grain size.
Fracture Toughness of a Beta‐SiC Whisker
Authors: PETROVIC JOHN J. , ROOF RAYMOND B.
Published: October 2006

Tensile fracture from an internal defect allowed measurement of the fracture toughness, KIc3 and fracture surface energy, y, for a single‐crystal beta‐SiC whisker with (111) crystallographic orientation in the tensile direction. Values of KIc=3.23 MPa.m1/2 and γ=9.06 J/m2 were obtained.
Phase Transformation and Processing of Poly crystalline Gadolinium Selenide, GdSei.1.49
Authors: WEI G.C.
Published: October 2006

Polymorphic phase transformation in a thermoelectric material, GdSe1.49, from cubic to orthorhombic symmetry at temperatures from 800° to 1000°C causes a 1% volume expansion, which generates microcracks. Sintered polycrystalline cubic GdSe1.49 preforms with at least 97% densities were vacuum annealed at 900°C for 300 h to fully convert to the orthorhombic lattice, encapsulated in nickel containers, and then isostatically hot‐pressed. Hot‐pressing at or below 1000°C resulted in 96%‐dense orthorhombic GdSe1.49 polycrystals containing large pores, whereas hot‐pressing above 1200°C produced fully dense cubic polycrystals with a duplex microstructure. The electrical resistivity of the orthorhombic GdSe1.49 (hot‐pressed below 1000°C) was about 5 times that of the as‐sintered cubic GdSe1.49; the increase appears to be related to the presence of the orthorhombic phase, micro‐cracks, large pores, and a Se‐rich grain‐boundary phase in the hot‐pressed orthorhombic GdSei1.49.
Preparation of Silicon Nitride from Silica
Authors: ZHANG SHI‐CHANG , CANNON W. ROGER
Published: October 2006

The nucleation and growth of Si3N4 from a carbon‐Si02 mixture in an N2 atmosphere at 1400°C was studied by varying the specific surface area, particle size, and distribution of the Si02and carbon. Si3N4 yield increased and particle size decreased with increasing Si02 and carbon specific surface area. Manner of distribution appeared to have little effect but was difficult to assess. A model was proposed in which heterogeneous nucleation occurs on either the Si02 or C surfaces only in the early stages of the reaction. Growth occurs by the reaction
Chemical Polishing Behavior of Sodium β″‐Alumina Electrolytes
Authors: SINGH R. N.
Published: October 2006

Sodium ion conducting solid electrolytes based on sodium β″‐alumina phase, useful in sodium‐sulfur batteries, were exposed to phosphoric acid to determine the chemical polishing conditions. Under suitable conditions of acid concentration, exposure time, and exposure temperature, samples of sodium β″‐alumina were polished by phosphoric acid. The kinetics of polishing was studied, and a polishing mechanism is proposed. Insignificant effect of chemical polishing on the fracture strength of sodium β″‐alumina electrolyte was obtained.
Effect of Interlayers in Ceramic‐Metal Joints with Thermal Expansion Mismatches
Authors: Suganuma Katsuaki , Okamoto Taira , Koizljmi Mitsue , Shimada Masahiko
Published: October 2006

The internal stress resulting from the thermal expansion mismatch between alumina and steel with and without an interlayer was evaluated. On the basis of the calculation, alumina and steel were bonded using the interlayer method and hot isostatic pressing at 1273 to 1573 K under 100 MPa for 30 min. When a laminated interlayer (niobiumlmolybdenum) was used, a joint with high bonding strength was obtained.
Problems in the coupling of eye and hand in the sequential movements of children with Developmental Coordination Disorder
Authors: Wilmut K. , Wann J. P. , Brown J. H.
Published: October 2006

Background  Shifting gaze and attention ahead of the hand is a natural component in the performance of skilled manual actions. Very few studies have examined the precise co‐ordination between the eye and hand in children with Developmental Coordination Disorder (DCD).

Methods  This study directly assessed the maturity of eye–hand co‐ordination in children with DCD. A double‐step pointing task was used to investigate the coupling of the eye and hand in 7‐year‐old children with and without DCD. Sequential targets were presented on a computer screen, and eye and hand movements were recorded simultaneously.

Results  There were no differences between typically developing (TD) and DCD groups when completing fast single‐target tasks. There were very few differences in the completion of the first movement in the double‐step tasks, but differences did occur during the second sequential movement. One factor appeared to be the propensity for the DCD children to delay their hand movement until some period after the eye had landed on the target. This resulted in a marked increase in eye–hand lead during the second movement, disrupting the close coupling and leading to a slower and less accurate hand movement among children with DCD.

Conclusions  In contrast to skilled adults, both groups of children preferred to foveate the target prior to initiating a hand movement if time allowed. The TD children, however, were more able to reduce this foveation period and shift towards a feedforward mode of control for hand movements. The children with DCD persevered with a look‐then‐move strategy, which led to an increase in error. For the group of DCD children in this study, there was no evidence of a problem in speed or accuracy of simple movements, but there was a difficulty in concatenating the sequential shifts of gaze and hand required for the completion of everyday tasks or typical assessment items.
Rhythmic coordination of hand and foot in children with Developmental Coordination Disorder
Authors: Volman M. J. M. , Laroy M. E. , Jongmans M. J.
Published: October 2006

Background  Children with Developmental Coordination Disorder (DCD) have difficulties producing stable rhythmic bimanual coordination patterns in comparison with age‐related peers. Rhythmic coordination of non‐homologous limbs (e.g. hand and foot) is even more difficult to perform because of mechanical differences between the limbs. The aim of the present study is to investigate the stability of hand–foot coordination patterns of children with DCD.

Methods  Ten children with DCD (mean age 7.0 years, SD 1.1 years) and 16 control children (mean age 7.4 years, SD 1.3 years) participated in the study. They were asked to perform in‐phase or anti‐phase tapping movements in three different interlimb coordination combinations: (1) hand–hand (homologous), (2) hand–foot same body side (ipsilateral), and (3) hand–foot different body side (contralateral). Coordination stability was measured by the variability of the relative phase between the limbs under a ‘steady state’ (preferred) frequency condition, and by the critical frequency (i.e. the point at which loss of pattern stability was observed) in a condition in which the movement frequency was ‘scaled’ up (only anti‐phase tapping).

Results  Coordination patterns of children in the DCD group were less stable in all three limb combinations compared with controls. Further, hand–foot coordination patterns were less stable than hand–hand coordination patterns. With regard to hand–foot coordination, ipsilateral patterns were equally stable compared with contralateral patterns in the in‐phase task, but less stable in the anti‐phase task. No differential effects were found between the DCD and control groups across the different limb combinations, except for steady‐state anti‐phase coordination in the ipsilateral limb condition. This effect was due to a relatively good performance of the control children in this condition in comparison with the other limb combination conditions.

Conclusions  Children with DCD have difficulties producing stable rhythmic hand–foot coordination patterns compared with control children.
Motor, visual and egocentric transformations in children with Developmental Coordination Disorder
Authors: Williams J. , Thomas P. R. , Maruff P. , Butson M. , Wilson P. H.
Published: October 2006

Aim This study aimed to test the internal modelling deficit (IMD) hypothesis using the mental rotation paradigm.

Background According to the IMD hypothesis, children with Developmental Coordination Disorder (DCD) have an impaired ability to internally represent action. Thirty‐six children (18 DCD) completed four tasks: two versions of a single‐hand rotation task (with and without explicit imagery instructions), a whole‐body imagery task and an alphanumeric rotation task.

Results There was partial support for the hypothesis that children with DCD would display an atypical pattern of performance on the hand rotation task, requiring implicit use of motor imagery. Overall, there were no significant differences between the DCD and control groups when the hand task was completed without explicit instructions, on either response time or accuracy. However, when imagery instructions were introduced, the controls were significantly more accurate than the DCD group, indicating that children with DCD were unable to benefit from explicit cuing. As predicted, the controls were also significantly more accurate than the DCD group on the whole‐body task, with the accuracy of the DCD group barely rising above chance. Finally, and as expected, there was no difference between the groups on the alphanumeric task, a measure of visual (or object‐related) imagery.

Conclusions The inability of the DCD group to utilize specific motor imagery instructions and to perform egocentric transformations lends some support to the IMD hypothesis. Future work needs to address the question of whether the IMD itself is subgroup‐specific.
Laser capture microdissection of plant cells from tape‐transferred paraffin sections promotes recovery of structurally intact RNA for global gene profiling
Authors: Cai Suqin , Lashbrook Coralie C.
Published: October 2006

Laser capture microdissection and related technologies permit the harvest of individual cells and cell types. Isolation of either nucleic acids or proteins from laser‐captured cells supports such downstream applications as the construction of cell‐specific cDNA libraries and the profiling of expressed genes and proteins. The success of these endeavors is dependent upon the yield, purity and structural integrity of the macromolecules derived from harvested cells. Here, we report protocols that promote the isolation of structurally intact RNA from laser‐captured cells of paraffin‐embedded tissues. The use of a tape transfer system that obviates the need to wet paraffin sections prior to slide mounting significantly increases RNA structural quality. Integrity is assessed directly via electrophoretic separation of picogram–nanogram levels of total RNA isolated from multiple cell types, including those comprising Arabidopsis ovules, replums and stamen abscission zones. RNA prepared from specialized cells within siliques provided targets for profiling the Arabidopsis genome during replum cell development. Digital northern analysis of transcripts expressed near the threshold of the system's ability to score signal presence suggests that low‐abundance transcripts representing as little as ∼0.002% of total mRNA can be reliably detected. Microarray data reveal a significant shift from primary cell‐wall metabolism to lignin biosynthesis in replum tissues during fruit maturation.
Isolation and characterization of hydrogen‐oxidizing bacteria induced following exposure of soil to hydrogen gas and their impact on plant growth
Authors: Maimaiti Jiamila , Zhang Ye , Yang Jing , Cen Yan‐Ping , Layzell David B. , Peoples Mark , Dong Zhongmin
Published: October 2006

In many legumes, the nitrogen fixing root nodules produce H2 gas that diffuses into soil. It has been demonstrated that such exposure of soil to H2 can promote plant growth. To assess whether this may be due to H2‐oxidizing microorganisms, bacteria were isolated from soil treated with H2 under laboratory conditions and from soils collected adjacent to H2 producing soybean nodules. Nineteen isolates of H2‐oxidizing bacteria were obtained and all exhibited a half‐saturation coefficient (Ks) for H2 of about 1 ml l−1. The isolates were identified as Variovorax paradoxus, Flavobacterium johnsoniae and Burkholderia spp. using conventional microbiological tests and 16S rRNA gene sequence analysis. Seventeen of the isolates enhanced (57–254%) root elongation of spring wheat seedlings. Using an Arabidopsis thaliana bioassay, plant biomass was increased by 11–27% when inoculated by one of four isolates of V. paradoxus or one isolate of Burkholderia that were selected for evaluation. The isolates of V. paradoxus found in both H2‐treated soil and in soil adjacent to soybean nodules had the greatest impact on plant growth. The results are consistent with the hypothesis that H2‐oxidizing bacteria in soils have plant growth promoting properties.
Spatial practices and imaginaries: Experiences of colonial officers and development professionals
Authors: Kothari Uma
Published: October 2006

This paper explores the spatiality of colonial and postcolonial power and discourse as produced, performed and imagined by former British colonial service officers and contemporary UK international development professionals. It focuses on two key aspects of spatial practices. The first addresses the spaces inhabited by these colonial officers and development professionals overseas and how their locatedness, embedded or enclavic, shapes relationships to others. The second explores this distinctive social and spatial distancing through their relationship to, and imagined geographies of, home and away and how these are embodied in their institutional and cultural capital. The paper examines the regularities and consistencies that stand out from numerous individual practices through which both former colonial officers and development professionals negotiate the situations in which they live and work. It also specifies how authoritative management, privilege and distance informs their spatial practices despite changing global contexts and a more diverse composition of those who articulate contemporary relationships between ‘first’ and ‘third’ worlds. Finally, the paper suggests that the cultures which travelled over colonial space through being performed by colonial officers have been reworked throughout the postcolonial period, belying epochal historical periodizations that conjure up a clear disjuncture between colonial and development eras.
Claims: A postcolonial geographical critique of ‘partnership’ in Britain’s development discourse
Authors: Noxolo Patricia
Published: October 2006

This paper uses postcolonial theory to establish a critique of the concept of ‘partnership’ in the British Labour government’s 1997 White Paper on International Development, which is routed through the colonial metaphor of the British Commonwealth ‘family of nations’ to reproduce racialized hierarchies and deny mutuality in the contemporary development of Britain and its former colonies. In the course of this critique, the paper urges British geography to acknowledge its own postcoloniality, which will lead to a mainstreaming of concerns about global justice and provide intellectual resources to reimagine the geographies of postcolonial Britain.
‘Black skins–white masks’: Postcolonial reflections on ‘race’, gender and second generation return migration to the Caribbean
Authors: Phillips Joan , Potter Robert B.
Published: October 2006

This paper illustrates the opportunities afforded by the adoption of postcolonial discourse in development geography, drawing specifically on issues of transnationalism, hybridity and inbetweeness. The utility of such notions and associated approaches is illustrated by the authors’ current research on the migration of young, second generation and foreign‐born ‘Bajan‐Brits’ to the small Caribbean island nation of Barbados, the homeland of their parents. Focussing on issues of ‘race’ and gender, the paper examines the experiences of return migration among this cohort from an interpretative perspective framed within postcolonial discourse. It argues that notwithstanding the considerable sociocultural problems of adjustment encountered, these Bajan‐Brit ‘returnees’ may be seen as occupying positions of relative economic privilege. Theirs is a liminal space derived by virtue of having been born and/or raised in the UK and being of the black ‘race’. Accordingly, they are demonstrated to be both advantaged and disadvantaged; both transnational and national; and black but, in some senses, symbolically white.