bluuebunny/crossref_metadata_2025 huggingface dataset:
An atomic force microscope tip as a light source
Authors: Lulevich Valentin , Honig Chris , Ducker William A.
Published: December 2005

We present a simple method for causing the end of a silicon nitride atomic force microscope (AFM) tip to emit light, and we use this emitted light to perform scanning near-field optical microscopy. Illumination of a silicon nitride AFM tip by blue (488nm) or green (532nm) laser light causes the sharp part of the tip to emit orange light. Orange light is emitted when the tip is immersed in either air or water; and while under illumination, emission continues for a period of many hours without photobleaching. By careful alignment of the incident beam, we can arrange the scattered light to decay as a function of the tip-substrate separation with a decay length of 100–200nm. The exponential decay of the intensity means that the emitted light is dominated by contributions from parts of the tip that are near the sample, and therefore the emitted orange light can be used to capture high-resolution near-field optical images in air or water.
Comment on “A large low-field magnetoresistance of CrO2∕(CrO2∕Cr2O3) powder compact with two coercivities” [J. Appl. Phys. 97, 073907 (2005)]
Authors: Ju Sheng , Cai Tian-Yi , Li Z. Y.
Published: December 2005

In a recent paper, Wang et al. [J. Appl. Phys. 97, 073907 (2005)] have studied the intergranular tunneling magnetoresistance (TMR) in CrO2∕(CrO2∕Cr2O3) powder compacts. However, the mistakes in their equations for TMR lead to the inconsistency between their model and experimental data. In this Comment, we have presented a proper equation for TMR, as well as explanations for the temperature dependence of TMR in half-metallic CrO2 composites.
Local p-type conductivity in zinc oxide dual-doped with nitrogen and arsenic
Authors: Krtschil A. , Dadgar A. , Oleynik N. , Bläsing J. , Diez A. , Krost A.
Published: December 2005

A doping approach for p-type ZnO is reported which is reproducible and long-time stable. For p-type doping the zinc oxide layers were doped simultaneously with nitrogen and arsenic in metal organic vapor phase epitaxy. The conductivity type of the layers was investigated by scanning capacitance microscopy, a technique based on local capacitance-voltage analysis (C-V) with submicron spatial resolution. Depending on the growth parameters, largely extended p-type domains were observed, surrounded by n-type regions. The differences in local conductivity type are directly correlated to the topography as measured with atomic force microscopy revealing p-type for smooth, two-dimensional surfaces and n-type signals in the case of three-dimensional island growth or structural defects, i.e., microcracks or surface pits.
The formation mechanism of aluminum oxide tunnel barriers: Three-dimensional atom probe analysis
Authors: Petford-Long A. K. , Ma Y. Q. , Cerezo A. , Larson D. J. , Singleton E. W. , Karr B. W.
Published: December 2005

Magnetic tunnel junctions have applications in a range of spin-electronic devices. The functional properties of such devices are critically dependant on the nanoscale morphology of the insulating barrier (usually only a few atomic layers thick) that separates two ferromagnetic layers. Here we report atomic-resolution three-dimensional visualization of magnetic tunnel junctions with an aluminum oxide barrier, using three-dimensional atom probe analysis and cross-sectional high resolution electron microscopy. Our results on barriers with a range of degrees of oxidation have enabled a mechanism for the oxidation to be proposed. Low oxidation times result in discrete oxide islands and further oxidation leads to a more continuous, but nonstoichiometric, barrier. Post-deposition annealing leads to an increase in the barrier area and near stoichiometric chemistry with evidence that oxidation proceeds along the top of grain boundaries in the underlying CoFe. Our three-dimensional visualization enables us to show that even perforated barriers (formed at shorter oxidation times) can have reasonable transport properties.
Equation-of-state measurements for polystyrene at multi-TPa pressures in laser direct-drive experiments
Authors: Ozaki N. , Ono T. , Takamatsu K. , Tanaka K. A. , Nakano M. , Kataoka T. , Yoshida M. , Wakabayashi K. , Nakai M. , Nagai K. , Shigemori K. , Yamanaka T. , Kondo K.
Published: December 2005

Equation-of-state (EOS) measurements for polystyrene in TPa (10Mbar) pressure regions are presented. Polystyrene Hugoniot data were obtained up to 2.7TPa using impedance matching techniques with laser direct drive at the GEKKO/HIPER laser facility [N. Miyanaga et al., in Proceedings of the 18th International Conference on Fusion Energy (IAEA, Sorrento, Italy, 2001), IAEA-CN-77] The results were compared with theoretical models and previous experimental data and found to be in good agreement with the previous data obtained by different drive and diagnostic techniques.
Temperature independence of the spin-injection efficiency of a MgO-based tunnel spin injector
Authors: Salis G. , Wang R. , Jiang X. , Shelby R. M. , Parkin S. S. P. , Bank S. R. , Harris J. S.
Published: December 2005

The spin polarization of electrons injected into GaAs from a CoFe∕MgO(100) tunnel spin injector is inferred from the circular polarization of light emitted from a GaAs-based quantum well (QW) detector. The circular polarization strongly depends on the spin and electron hole recombination lifetimes in the QW. Using time-resolved optical techniques, we show that these lifetimes are highly temperature dependent. A peak in the charge lifetime versus temperature is likely responsible for the previously observed dip in the electroluminescence polarization. Evidence for a temperature-independent spin injection efficiency of ∼70% from 10 K to room temperature is found.
Artificial domain structures realized by local gallium focused Ion-beam modification of Pt∕Co∕Pt trilayer transport structure
Authors: Aziz A. , Bending S. J. , Roberts H. , Crampin S. , Heard P. J. , Marrows C. H.
Published: December 2005

We demonstrate that a high-resolution Ga focused ion beam can be used to introduce artificial domain structures in Pt(1.6nm)∕Co(0.5nm)∕Pt(3.5nm) trilayer transport structures. We have used thin SiO2 overlayers to control the effective energy and dose of Ga ions at the Pt∕Co interface. The extraordinary Hall effect (EHE) was used to characterize the magnetic properties of the patterned films. Using 30keV Ga ions and SiO2 overlayer thicknesses in the range of 0–24nm, we achieve complete control of the coercive field of our Pt∕Co∕Pt trilayer structures. The magnetization reversal mechanism for an artificial domain of size of 3×0.5μm2 is investigated using EHE.
High-efficiency red light-emitting diodes based on polyfluorene copolymers with extremely low content of 4,7-di-2-thienyl-2,1,3-benzothiadiazole-comparative studies of intrachain and interchain interaction
Authors: Luo Jie , Peng Junbiao , Cao Yong , Hou Qiong
Published: December 2005

High-efficiency red light-emitting diodes based on poly(9,9-dioctylfluorene) (PFO) doped chemically into the polymer main chain with extremely low dopant content of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DBT) (comonomer ratio:99.9∕0.1) are realized. External quantum efficiency of PFO-DBT0.1 reached 2.66% (photon/electron) with a luminance efficiency of 2.5cd∕A, significantly higher than that of the device with high DBT content. The copolymer exclusively emits red light peaked at 615nm due to strong intrachain energy transfer. Comparing photophysical properties and device performance between single copolymer PFO-DBT0.1 and blends with the same DBT composition by adding neat PFO into a PFO-DBT15, PFO-DBT25, or PFO-DBT35 copolymers, we concluded that energy transfer via intrachain interaction along a conjugated polymer main chain is more efficient than via interchain interaction in such copolymers and that chemically doped copolymers show higher device performance than polymer blend.
Periodic pillar structures by Si etching of multilayer GeSi∕Si islands
Authors: Zhong Z. , Katsaros G. , Stoffel M. , Costantini G. , Kern K. , Schmidt O. G. , Jin-Phillipp N. Y. , Bauer G.
Published: December 2005

Laterally aligned multilayer GeSi∕Si islands grown on a patterned Si (001) substrate are disclosed by selective etching of Si in a KOH solution. This procedure allows us to visualize the vertical alignment of the islands in a three-dimensional perspective. Our technique reveals that partly coalesced double islands in the initial layer do not merge together, but instead gradually reproduce into well-separated double islands in upper layers. We attribute this effect to very thin spacer layers, which efficiently transfer the strain modulation of each island through the spacer layer to the surface. The etching rate of Si is reduced in tensile strained regions, which helps to preserve sufficient Si between the stacked islands to form a periodic array of freestanding and vertically modulated heterostructure pillars.
Dielectric properties of ultrathin SiO2 slabs
Authors: Shi N. , Ramprasad R.
Published: December 2005

First-principles total energy calculations have been performed to determine the extent to which surfaces impact the dielectric properties of ultrathin dielectric materials. SiO2 (0001) slabs in α-quartz phase with various thicknesses were considered in this study, using a new method that allows for the partitioning of the surface and bulk contributions to the total field-induced polarization. It was found that the bulk polarization and the dielectric constant can be determined even from ultrathin films terminated with Si atoms, and that surface effects do not significantly impact the dielectric properties of (0001) α-quartz slabs.
Efficiency improvement in thin-film solar cell devices with oxygen-containing absorber layer
Authors: Emziane M. , Durose K. , Halliday D. P. , Bosio A. , Romeo N.
Published: December 2005

The CdTe∕CdS solar cell devices were grown using a dry process consisting of sputtering for the transparent conducting oxide and CdS window layers, and close-space sublimation for CdTe absorber layer. These devices were back contacted using Mo∕Sb2Te3 sputtered layers following the CdCl2 activation process carried out in air. It was shown that when oxygen is intentionally introduced in the CdTe layer during its growth, this leads to a significant improvement in all the device parameters yielding an efficiency of 14% compared to 11.5% for devices fabricated in the same conditions but without intentional oxygen incorporation in CdTe. The data obtained were not altered following a light soaking. The devices were investigated by quantitative secondary ion mass spectrometry, which allowed insight into the distribution and amount of oxygen and chlorine within the entire device structure. Both impurities showed an increased concentration throughout the CdTe absorber layer.
High-bias-induced structure and the corresponding electronic property changes in carbon nanotubes
Authors: Chen S. , Huang J. Y. , Wang Z. , Kempa K. , Chen G. , Ren Z. F.
Published: December 2005

Atomic-scale microstructure changes of carbon nanotubes under high bias∕high current conditions were studied by in situ high-resolution transmission electron microscopy. We found that high bias voltage caused significant structure changes, such as crystallization and elimination of amorphous coating on the surface of nanotube walls, removal of nanotube walls, and formation of atomic-scale kinks. These structural changes are attributed to high temperatures induced by high bias resistive heating on the nanotubes. These structural changes cause dramatic electronic property changes of the nanotubes correspondingly. The results provide an efficient route to tailor the electronic properties of nanotubes by appropriate structural modifications.
Computed tomography algorithm based on diffraction-enhanced imaging setup
Authors: Zhu P. P. , Wang J. Y. , Yuan Q. X. , Huang W. X. , Shu H. , Gao B. , Hu T. D. , Wu Z. Y.
Published: December 2005

Recently taking advantage of the novel diffraction-enhanced imaging (DEI) method, one very effective and practical phase contrast imaging technique—a new x-ray computed tomography scheme based on DEI (DEI-CT) showed promising results, really superior to those of conventional CT imaging. In this letter, we show that the application of the conventional CT reconstruction algorithm is not always satisfactory for the new DEI-CT imaging and a new mathematical framework for imaging reconstruction is presented. Experimental data collected at the Beijing synchrotron radiation facility are also discussed using the new algorithm.
Surface conductive layers on oxidized (111) diamonds
Authors: Ri Sung-Gi , Takeuchi Daisuke , Kato Hiromitsu , Ogura Masahiko , Makino Toshiharu , Yamasaki Satoshi , Okushi Hideyo , Rezek Bohuslav , Nebel Christoph E.
Published: December 2005

Surface conductive layers (SCL) on oxidized (111) diamonds with smooth surfaces after exposure to air were detected and characterized by Hall effect measurements. Hall effect measurements show that the conductivity is p type with sheet hole concentrations around of 1012cm−2 and Hall mobilities between 5 and 130cm2∕Vs. The SCL vanishes by thermal annealing at a temperature higher than 460K in He atmosphere, and recovers in air. These characteristics are similar to those generated by hydrogen termination. The experiments revealed that these SCLs are present on boron doped (111) and undoped (111) diamond films with smooth surfaces and natural IIa (111) diamonds, but not on (111) diamond films with rough surfaces and not on (100) diamonds.
Signal processing by opto-optical interactions between self-localized and free propagating beams in liquid crystals
Authors: Pasquazi Alessia , Alberucci Alessandro , Peccianti Marco , Assanto Gaetano
Published: December 2005

The reorientational nonlinearity of nematic liquid crystals enables a self-localized spatial soliton and its waveguide to be deflected or destroyed by a control beam propagating across the cell. We demonstrate a simple all-optical readdressing scheme by exploiting the lens-like perturbation induced by an external beam on both a nematicon and a copolarized guided signal of different wavelength. Angular steering as large as 2.2deg was obtained for control powers as low as 32mW in the near infrared.
Preparation and Crystal Structure of Silver(I) Anthranilate
Authors: Smith Graham , Kennard Colin H. L. , Byriel Karl A.
Published: December 2005

Silver(I) anthranilate,
[Ag2(C7H6NO2)2]n,
was isolated as the major constituent in the attempted preparation of the
adduct of anthranilic acid (2-aminobenzoic acid) with silver(I)
p-toluenesulfonate and its structure has been determined
by using single-crystal X-ray diffraction. Crystals of the complex are
monoclinic, space group P
21/n, with two dimers in a
cell of dimensions a 5·3516(8),
b 4·9746(2), c
25·386(5) Å, β 91· 547(8)°. The complex repeating
unit comprises a distorted centrosymmetric biscarboxylato(-O,O′)-bridged
dimer [Ag−O, 2·223, 2·409(4) Å; Ag---Ag
2·9128(9) Å] but has, in addition, a third bond to an
adjacent amine nitrogen [Ag−N, 2·301(5) Å], which
extends the structure into a zigzag chain polymer. The stereochemistry about
each Ag centre is distorted trigonal planar [angle range,
89·9−142·9(2)°]. Relatively short inter-dimer
Ag---Ag separations [2·989(1) Å] are also present.
Improved Epoxidation Methodology for Synthesis of the Highly Selective β2-Adrenoceptor Antagonist ICI 118551 [erythro (±)-3-Isopropylamino-1-(7-methylindan-4-yloxy)butan-2-ol]
Authors: Pegg Graham G. , Badran Terry W. , Hoey Andrew J. , Jackson Clifford M. , Sillence Martin N.
Published: December 2005

In this communication we describe a much improved methodology for the
synthesis of the selective β2-adrenoceptor
antagonist ICI 118551 (1), a procedure which overcomes capricious fractional
crystallization and epoxidation methodologies described for its original
preparation. Our approach involving a bromohydrin precursor to the key epoxide
intermediate (7) yielded an 85 : 15 mixture of the in
threo/erythro isomers of (7) which could be conveniently
separated by flash chromatography on amine-pretreated silica. This new
approach proved much more successful than attempts to separate the precursor
alkene isomers (6) by fractional crystallization as described in the original
patent literature. The product (1) obtained by using our methodology was found
to have identical pharmacological properties to authentic ICI 118551 when
tested both in vitro and in vivo.
Synthesis, Structures and Spectroscopic Properties of 1 : 1 Complexes of Gold(I) Halides with Tricyclohexylphosphine, [Au(PCy3)X], X = Cl, Br and I
Authors: Bott Raymond C. , Bowmaker Graham A. , Buckley Robbie W. , Healy Peter C. , Perera M. C. Senake
Published: December 2005

Two-coordinate gold(I) complexes, [Au(PCy3)X]
(PCy3 = tricyclohexylphosphine, X = Cl, Br
and I), have been prepared by reaction of stoichiometric quantities of
[NBu4] [AuX2]
and PCy3 in dimethylformamide and, for X = Cl and
Br, by anodic dissolution of metallic gold in a solution of aqueous HX and
PCy3 in acetonitrile. The complexes were characterized by solution and
solid-state 31 P n.m.r. spectroscopy, far-infrared
spectroscopy and single-crystal X-ray structure determinations. The chloride,
bromide and iodide complexes form an isomorphous series, crystallizing in the
triclinic space group P 1- (a ≈
9·3, b ≈ 10·3, c
≈ 10·9 Å, α ≈ 88, β ≈ 80, γ ≈ 77°)
as discrete molecules which stack in parallel head-to-tail mode to form a
zigzag chain of gold atoms along the crystallographic c
axis. Au ··· Au separations are 5·71, 6·20
Å for X = Cl, 5·72, 6·17 Å for X = Br
and 5·74, 6·20 Å for X = I. The iodide also
crystallizes as an orthorhombic form in space group Pnma
(a 16·809(4), b
14·373(5), c 8·623(3) Å) with a
different conformational structure for the PCy3 ligand
and loss of the zigzag chain structure. Far-infrared spectra of the complexes
show ν(AuX) at 332, 324 cm-1 for X = Cl and
232 cm-1 for X = Br with multiple bands in the
region 150−200 cm-1 for both iodide complexes,
precluding definitive assignment of ν(AuI). Solution 31 P n.m.r. spectra
in chloroform give sharp single peaks with chemical shifts of 54·5,
56·6 and 59·9 ppm for X = Cl, Br and I respectively. The
solid-state CPMAS 31 P n.m.r. spectra also yield single peaks with chemical
shifts of 55 (Cl), 58 (Br) and 63 ppm (I) for the triclinic complexes and 57
ppm for the orthorhombic iodide. The chemical shift differences between the
two forms of the iodide and between the complexes in the solution and solid
states are ascribed to variations in the conformational structure of the
phosphine ligands.
Structure Revision and Cytotoxic Activity of the Scabrosin Esters, Epidithiopiperazinediones from the Lichen Xanthoparmelia scabrosa
Authors: Ernst-Russell Michael A. , Elix John A. , Chai Christina L. L. , Hockless David C. R. , Hurne Alanna M. , Waring Paul
Published: December 2005

The scabrosin esters (1){(4), isolated from the lichen
Xanthoparmelia scabrosa, were reanalysed by modern one-
and two-dimensional n.m.r. spectroscopic methods, including
15N n.m.r. spectroscopy, and single-crystal X-ray
structural analysis. This reinvestigation has resulted in the unambiguous
structure elucidation and complete spectral assignment of these metabolites
and established them to be a family of epidithiopiperazinedione derivatives. A
new scabrosin ester, scabrosin butyrate hexanoate (5), has also been isolated
and its structure determined, including assignment of absolute configuration.
Several scabrosins were found to exhibit potent cytotoxic activity against the
murine P815 mastocytomia cell line (IC50
c. 0·5 µM) and the human breast MCF7
carcinoma cell line (IC50 c. nM).
Compounds which contain a dithiopiperazinedione moiety have not previously
been identified in lichenized fungi.
Homonuclear PdII and PtII and heteronuclear PdII-AuI and PtII-AuI complexes of a tripod triphosphine ligand: synthesis, characterization and reactions with molecules of biological relevance
Authors: Sevillano Paloma , Habtemariam Abraha , Seijo M. Inés García , Castiñeiras Alfonso , Parsons Simon , García M. Esther , Sadler Peter J.
Published: December 2005

Complexes of the type Pd(tripod)X2 [tripod =
MeC(CH2PPh2)3;
X = Cl (1), Br (2), I (3)] and Pt(tripod)X2
[X = Cl (4), Br (5), I (6)] have been synthesized. In these
complexes tripod acts as a bidentate chelating ligand. The uncoordinated
phosphorus atom can bind to AuI to form the bimetallic
complexes PdAu(tripod)X3 [X = Cl (7), Br
(8), I (9)] and PtAu(tripod)X3 [X = Cl
(10), Br (11), I (12)]. Complexes (1)–(12) have been characterized
by microanalysis, f.a.b. mass spectrometry, i.r. spectroscopy,
31P and 195Pt n.m.r.
spectroscopies, and conductivity measurements. The structures of complexes
(1), (4) and (11), as well as that of the unusual complex
Cl2Pt(tripod)AuBr0.5Cl0.5
(13), isolated from reaction of Pt(tripod)Br2 (5), and
[Au(thiodiglycol)Cl], have been determined. All complexes show
square-planar geometry for PdII or
PtII and linear geometry for AuI.
The X-ray crystal structure of (1) showed partial oxidation of the dangling
phosphorus of the ligand in 50% of the molecule distributed randomly
over the lattice. Reactions of complex (4),
Pt(tripod)Cl2, with the tripeptide glutathione (GSH)
showed the formation of
[Pt2(tripod)2(GS-µ–S)2]2+
(15a). No reaction with N-acetyl-L-methionine (AcMet) or
guanosine 5´-monophosphate (5´-GMP) was observed. Reactions of
[Pt(tripod–O)(ONO2)2]
(14) with GSH resulted in the formation of
[Pt2(tripod–O)2(GS-µ-S)2]2+
(15b). Displacement of the S-containing molecules by 5´-GMP in the
presence of AuI, via Pt–S bond cleavage, was
observed for complex (15b). PtAu(tripod)Cl3 (10) reacted
with GSH, with initial attack on the AuI centre.
Improved synthetic route to enantiomerically pure samples of the tetrahydropyran-2-ylacetic acid core associated with the phytotoxic polyketide herboxidiene
Authors: Banwell Martin G. , McLeod Malcolm D. , Premraj Rajaratnam , Simpson Gregory W.
Published: December 2005

The phosphine oxide (2), which embodies the tetrahydropyran-2-ylacetic acid
core associated with the phytotoxic polyketide herboxidiene (1) and which is a
key intermediate in a projected synthesis of this natural product, has been
prepared in a highly enantio- and diastereo-selective manner. The pivotal
steps in this new and improved synthesis of compound (2) involve
Katsuki–Sharpless asymmetric epoxidation of the allylic alcohol (4) to
give epoxide (7) and subsequent ring-cleavage of the latter compound with
trimethylaluminium to give diol (9). The derived acetate (10) is then readily
ozonolysed to give the previously reported aldehyde (11), although now in high
enantiomeric excess. Compound (11) can be elaborated, by established
chemistry, to the target oxide (2).
Introduction to Supramolecular Chemistry By Helena Dodziuk
Authors: Sherburn Michael
Published: December 2005

Introduction to Supramolecular ChemistryBy Helena DodziukKluwer Academic Publishers, The Netherlands.December 2001, 364 pp.ISBN 1402002149Hardcover, 82.00 GBP.Introduction to Supramolecular Chemistry by Dr Helena Dodziuk of the Institute of Physical Chemistry, Polish Academy of Sciences, is a broad summary of chemical aspects of supramolecular science. * Dr Michael Sherburn is a senior lecturer in organic chemistry at the School of Chemistry, the University of Sydney.
N,N-Dialkyl-N´-Chlorosulfonylchloroformamidines in Heterocyclic Synthesis. II. Thiazolo-, Thiadiazolo-, and Oxadiazolo-Fused [1,2,4,6]Thiatriazine Dioxides
Authors: Fallon Gary D. , Francis Craig L. , Johansson Katarina , Liepa Andris J. , Woodgate Ruth C. J.
Published: December 2005

N,N-dialkyl-N′-chlorosulfonylchloroformamidines 1 were treated with 2-aminothiazoline, 2-aminothiazoles, 2-aminobenzothiazoles, 2-amino-1,3,4-thiadiazoles, and 2-amino-1,3,4-oxadiazoles to give a 6,7-dihydrothiazolo[3,2-b][1,2,4,6]thiatriazine dioxide 3, a 6,7-dihydrothiazolo[2,3-c][1,2,4,6]thiatriazine dioxide 4, thiazolo[3,2-b][1,2,4,6]thiatriazine dioxides 5, [1,2,4,6]thiatriazino[3,2-b]benzothiazole dioxides 7, a [1,2,4,6]thiatriazino[3,4-b]benzothiazole dioxide 8, [1,3,4]thiadiazolo[2,3-c][1,2,4,6]thiatriazine dioxides 10, [1,3,4]thiadiazolo[3,2-b][1,2,4,6]thiatriazine dioxides 11, [1,3,4]oxadiazolo[2,3-c][1,2,4,6]thiatriazine dioxides 13, and [1,3,4]thiadiazolo[3,2-b][1,2,4,6]thiatriazine dioxides 14. Compounds 3, 4, 5, 7, 8, 10, 11, 13, and 14 are derivatives of new ring systems.
Construction of the 1,2,3,4-Tetrahydro-1,4,6,2-oxathiazaphosphorine Ring System
Authors: Johnson Wynona M. , Turner Kathleen A.
Published: December 2005

The novel 1,2,3,4-tetrahydro-1,4,6,2-oxathiazaphosphorine ring system has been prepared by reaction of the sodium salt of diethyl mercaptomethylphosphonate with nitrile oxides, followed by cyclization of the resulting hydroximinoyl sulfide. The stability of the new ring system is investigated.
Predictive Human Intestinal Absorption QSAR Models Using Bayesian Regularized Neural Networks
Authors: Polley Mitchell J. , Burden Frank R. , Winkler David A.
Published: December 2005

An oral dosage form is generally the most popular with patients. Many drug candidates fail in late development because of unfavourable absorption and pharmacokinetic profiles, or toxicity, among other factors (ADMET properties). This contributes to the fall in the efficiency of the pharmaceutical industry and to the rise in health costs. The ability to predict ADMET properties of drug leads can contribute to overcoming this problem. We have modelled intestinal absorption using several types of molecular descriptors and a non-linear Bayesian regularized neural network. Our models show very good predictive properties and are able to account for essentially all of the variance in the data that is not due to experimental error.
Structural Systematics of Rare Earth Complexes. XII Solvated 1 : 1 Adducts of Some Lanthanoid(III) Carboxylates with 1,10-Phenanthroline and 2,2′:6′,2″-Terpyridine
Authors: Kepert Cameron J. , Semenova Lioubov I. , Wei-Min Lu , Skelton Brian W. , White Allan H.
Published: December 2005

A room-temperature single-crystal X-ray structure determination of the 1 : 1
adduct of 1,10-phenanthroline (`phen") with lutetium(III) acetate
(as its dihydrate) is recorded. Crystals are triclinic,
P 1, a 12·430(8),
b 10·681(4), c
8·134(8) Å, α 74·76(6), β 84·81(7), γ
74·29(4)°, Z = 2 f.u.; conventional
R on |F| was
0·031 for No 3939
independent ‘observed’ (I >
3σ(I)) diffractometer reflections. The complex
[(N,N′-phen)(O,O′-ac)Lu(O-ac-O′)4Lu(O,O′-ac)(N,N′-phen)].2H2O
is binuclear, the lutetium being eight-coordinated by bidentate phen and ac
(acetate) ligands and four oxygen atoms from the bridging acetate ligands.
Also recorded is the structural characterization of 1 : 1
Lu(ac)2Cl/tpy (tpy =
2,2′:6′,2″-terpyridine) as its pentahydrate; this complex is
triclinic, P 1, a
12·410(3), b 11·559(4),
c 9·976(4) Å, α 85·19(3),
β 70·30(3), γ 65·70(2)°, Z
= 2, R 0·049 for
No 4717. The complex is shown to
be
[(tpy)(H2O)2Lu(O2CCH3)2]Cl.3H2O,
with the lutetium nine-coordinated by tridentate tpy, a pair of bidentate
acetates and two unidentate water molecules, with the chloride uncoordinated.
Structural characterizations of a number of 1 : 1 adducts of variously
solvated lanthanoid(III) trichloroacetates, Ln(tca)3,
with tpy are also recorded. Yb(tca)3/tpy/MeOH (1
: 1 : 1) is triclinic, P 1, a
14·016(4), b 12·951(5),
c 9·604(3) Å, α 73·89(3),
β 76·56(3), γ 69·20(3)°, Z
= 2 f.u., R 0·057 for
No 4465. The complex is
mononuclear, the eight-coordinate
N3YbO5 array containing tridentate
tpy, unidentate methanol, and two unidentate and one bidentate chelating
anions. 1 : 1 : 1
Ln(tca)3/tpy/OH2 adducts
for Ln = La(-)Nd are triclinic, P 1,
a ≈ 13·4, b ≈
12·47, c ≈ 11·5 Å, α ≈
114·5, β ≈ 89·9, γ ≈ 115·6°,
Z = 1 binuclear array, R
0·061, 0·071 for No
3240, 2394. The two Ln atoms are
O,O′-bridged by a pair of
anions, the N3LnO6 nine-coordinate
lanthanoid environment being completed by a tridentate tpy, one water, one
unidentate and one bidentate anion. A 1 : 1 : 1
Lu(tca)3/tpy/OH2 array, by
contrast, is triclinic, P 1, a
16·569(8), b 14·815(5),
c 14·375(6) Å, α 62·05(3),
β 81·35(4), γ 77·97(3)°, Z
= 4 ‘mononuclear’ f.u., R
0·067 for No 6710. The
array, remarkably, contains species of both of the above types in a 1 : 2
binuclear-to-mononuclear ratio, but with water replacing methanol in the
mononuclear array.
Structural Systematics of Rare Earth Complexes. XIV Hydrated 1 : 1 Adducts of Lanthanoid(III) Nitrates with 2,2′:6′,2″-Terpyridine
Authors: Semenova Lioubov I. , White Allan H.
Published: December 2005

Room-temperature single-crystal X-ray structure determinations are recorded
for (hydrated) lanthanoid(III)
nitrate/2,2′:6′,2″-terpyridine (‘tpy’) (1 :
1) complexes; all are of the form
Ln(NO3)3/tpy/H2O(1
: 1 :x),
[(tpy)Ln(O2NO)2(OH2)y](NO3)(.z
H2O), and form two series of compounds. For Ln =
La(-)Gd, the complexes are
[(tpy)Ln(O2NO)2(OH2)3](NO3),
the lanthanoid atom being ten-coordinate; crystals are triclinic,
P 1, a ≈ 11·8,
b ≈ 11·3, c ≈
8·9 Å, α ≈ 75, β 69, γ ≈ 89°,
Z = 2 f.u., conventional R
on |F| 0·045, 0·062 for
No 4513, 2710 independent
‘observed’ (I >
3σ(I)) diffractometer reflections for Ln =
La, Gd respectively. For Ln = Tb(-)Lu, a different form is found:
monoclinic, P
21/c, a
≈ 8·8, b ≈ 11·5,
c ≈ 23·8 Å, β ≈ 111°,
Z = 4, R 0·055,
0·037, 0·056 for No
2427, 3079, 1857 for Ln = Tb, Lu, Y respectively, the form of the
complex being
[(tpy)Ln(O2NO)2(OH2)2](NO3).2H2O,
with nine-coordinate lanthanoid. Crystallization of the Ln = La adduct
from methanol yields an adduct of
La(NO3)3/tpy/MeOH (1 : 1 : 2)
[(tpy)La(O2NO)3(HOMe)2]
stoichiometry with 11-coordinate lanthanum. Crystals are triclinic,
P 1, a 12·361(2),
b 12·244(3), c
7·753(2) Å, α 96·56(2), β 103·22(2),
γ 91·16(2)°, Z = 2,
R 0·037 for
No 6597.
Structural Systematics of Rare Earth Complexes. XV Tris(2,2′:6′,2″-terpyridine)lanthanoid(III) Tris(perchlorate) Complexes
Authors: Semenova Lioubov I. , Sobolev Alexander N. , Skelton Brian W. , White Allan H.
Published: December 2005

Room-temperature single-crystal X-ray structure determinations of the 1 : 3
adducts of the trivalent lanthanoid perchlorates with
2,2′:6′,2″-terpyridine (‘tpy’) as crystallized
from acetonitrile are recorded. The Ln = La complex is the only one of
its structural type, being modelled as
La(ClO4)3/tpy/MeCN/H2O
(1 : 3 : 2 :2/3), trigonal P
3c1, Z = 6,
a 13·063(7), c
53·04(4) Å, recorded on an interim basis, with conventional
R on |F|
0·081 for No 2889
‘observed’ (I
>3σ(I)) reflections. For Ln = Ce, (Pr,
Sm,) Eu and, by presumption, other intermediate members, a monosolvate is
found, monoclinic P
21/n, a
≈ 9·3, b ≈ 21·1,
c ≈ 24·7 Å, β ≈ 91°,
Z = 4, R being
0·045, (0·060, 0·049,) 0·047 for
No 4420, (4199, 3931,) 3713. The
Ln = Eu adduct has also been obtained unsolvated in a form
representative of Ln = Eu, Lu and, by presumption, intermediate
members, as well as Y, which is monoclinic C
2/c, Z = 4,
R being 0·051, 0·044, 0·061 for
No 4386, 4407, 3713. All
monoclinic systems are of the form [Ln(tpy)3]
(ClO4)3(.S),
Ln being nine-coordinate, and in the case of the C
2/c phase lying on a crystallographic
2 axis. The Ln = La adduct was modelled with
three independent cations, all with crystallographic 3
symmetry, two with their coordination number augmented by the approach of
solvent along the 3 axis.
Temperature Dependence of the Crystal Structure of Ru4(µ4-C2H2)(CO)9(η-PhMe)
Authors: Bruce Michael I. , Skelton Brian W. , Zaitseva Natasha N. , White Allan H.
Published: December 2005

The thermal reaction between
Ru4(µ4-C2H2)(CO)12
and toluene afforded
Ru4(µ4-C2H2)(CO)9(η-PhMe),
whose crystal and molecular structures, determined at c.
300 and 153 K, are reported [triclinic, P 1;
a ≈ 8 . 0; b ≈ 10
. 4; c ≈ 13 . 7 Å,
a ≈ 87; b ≈ 89 . 7;
γ ≈ 70°, Z = 2; conventional
R values on |F| at
convergence were 0 . 027 (300 K), 0 . 020 (153 K) for 4561, 4761
independent ‘observed’ [F
>4σ(F)] reflections,
respectively]. At low temperature, the structure is a nicely ordered
Ru4 butterfly with a
C2H2 ligand sitting between the
wing tips and an η6 -PhMe
ligand attached to one of the wing-tip atoms along the extension of the axis
between them. At 300 K, a disordered component is evident, 9% occupancy
of the wing-tip atom appended to toluene being displaced by 0 . 701(8)
Å so that the bonding to the toluene approaches
η2; this is accompanied by a
counterpart displacement of one of the hinge Ru atoms. It is suggested that
this is the first stage of a putative migration of the arene from wing-tip to
hinge Ru atoms.
X-Ray Crystal Structure of N-[3-(Diethylaminomethyl)-4- hydroxyphenyl]acetamide and its Hydrochloride Salt. Two Forms of an Important Precursor in the Synthesis of Anti-Tuberculosis Drugs
Authors: Latif Tariq , Javed Tariq , Lynch Daniel E. , Pryce Robert J. , Byriel Karl A.
Published: December 2005

N-[3-(Diethylaminomethyl)-4-hydroxyphenyl]acetamide
(dmhpa) and its hydrochloride salt (dmhpaH+
Cl−) have been prepared and their X-ray crystal
structures determined. The structure of dmhpa comprises an intramolecular
hydrogen bond between the hydroxy group and the diethylaminomethyl nitrogen
and an intermolecular association between adjacent
N-acetamide groups resulting in a non-centrosymmetric
interdigitated ‘V’ polymeric network. Quantitative non-linear
optical measurements on a powdered sample of dmhpa revealed a second harmonic
signal of two-thirds the intensity of a urea standard. In contrast, the
hydrochloride salt is formed via protonation of the diethylaminomethyl
nitrogen and resides in a complex hydrogen-bonded network which involves not
only the free chloride ion but also one water molecule per
dmhpaH+
Cl−.
Synthesis and Crystal Structures of Three Carboxylate- Bridged Tetranuclear Copper(II) - Lanthanide(III) Complexes of Ph3P+CH2CH2CO2−
Authors: Yang Yang-Yi , Ng Seik Weng , Chen Xiao-Ming
Published: December 2005

Three tetranuclear copper(II)–lanthanide(III) complexes of
triphenylphosphoniopropionate
(Ph3P+CH2CH2CO2−,tppp),
namely
[Cu2Ln2(tppp)8(H2O)8](ClO4)10·2H
2 O [Ln = EuIII, NdIII
or CeIII], were synthesized and characterized by
crystallography. The EuIII complex crystallizes in the
triclinic space group P1 – with
a 16.249(7), b 17.185(11),
c 17.807(11) Å, α 69.750(10), β
89.230(10), γ 84.070(10)˚, V 4639(5)
Å3, Z 1. In the crystal
structures, four tppp ligands bridge a pair of CuII and
tetraaquo-EuIII atoms (Cu···Eu
3.527(2) Å) through their µ2-carboxylato
ends to form a dinuclear subunit; two of these subunits are additionally
linked by one of the CuII -bonded carboxylato oxygen
ends, across a centre of inversion, to furnish a dimeric tetranuclear
[Cu(tppp)4
Eu(H2O)4]2
species (Cu···Cu 3.323(2) Å). This
CuII -bonded oxygen atom occupies the apical site of the
square-pyramidal coordination environment of the CuII
atom. The EuIII atom is eight-coordinated in a
square-antiprismatic geometry. The NdIII and
CeIII complexes are isomorphous to the
EuIII complex, and only minor differences in bond
lengths and bond angles involving the metal atoms are noted.
Four New β-Orcinol meta-Depsides from Pertusaria and Siphula Lichens
Authors: Elix John A. , Barclay Caroline E. , Wardlaw Judith H. , Archer Alan W. , Yu Sen-hua , Kantvilas Gintaras
Published: December 2005

The new depsides decarboxyhypothamnolic acid
[3-(2′,4′-dihydroxy-3′,6′-dimethylphenyloxycarbonyl)-2-
hydroxy-6-methoxy-4-methylbenzoic acid] (4) and cryptothamnolic acid
[3-(3′-formyl-2′-hydroxy-4′-methoxy-
6′-methylbenzoyloxy)-4,6-dihydroxy-2,5-dimethylbenzoic acid] (6)
have been detected in extracts of a Chinese Pertusaria
species together with hypothamnolic acid (3) and their structures implied by
means of chromatographic and spectroscopic comparisons with synthetic
materials. Two further new depsides, neothamnolic acid
[3-(5′,7′- dihydroxy-6′ -methyl-1′ -oxo-1′
,3′ -dihydroisobenzofuran-4′
-yloxycarbonyl)-2-hydroxy-6-methoxy-4- methylbenzoic acid] (8) and
lactothamnolic acid
[3-(6′-formyl-5′,7′-dihydroxy-1′-oxo-1′,3′-dihydroisobenzo-
furan-4′-yloxycarbonyl)-2-hydroxy-6-methoxy-4-methylbenzoic acid]
(9), have been isolated from the lichen
Siphula ramalinoides, and the structure of these
compounds followed from a combination of spectroscopic data, derivatization
and degradation experiments.
Walter C. Taylor
Authors: Mander Lew
Published: December 2005

… awarded the Einstein Medal by UNESCO …
Mortality and survivorship of the quokka (Setonix brachyurus) (Macropodidae : Marsupialia) in the northern jarrah forest of Western Australia
Authors: Hayward Matt W. , de Tores Paul J. , Augee Michael L. , Banks Peter B.
Published: December 2005

The potential for the quokka (Setonix brachyurus (Quoy & Gaimard, 1830)), a threatened macropodid marsupial, to increase in abundance following the initiation of predator control was investigated by determining the cause of deaths of radio-collared individuals. Predation was identified as a major cause of death followed by road kills. The non-parametric Kaplan–Meier method modified for staggered entry of individuals was used to estimate survivorship. Although males and females were affected differently by each cause of mortality, their overall survivorship did not differ significantly. Individuals alive at the beginning of the 25-month study had a 61% chance of surviving to the end. This represented an 81% chance of surviving for 1 year. There was no significant difference in survivorship between adults and juveniles. Current rates of adult and juvenile survivorship should allow population recovery, although none has been evident. Pouch young mortality is hypothesised to have inhibited the anticipated quokka population increase since the initiation of predator control. The observed expulsion of pouch young by females when threatened may be a primary predator avoidance strategy.
Increasing the target-specificity of the M-44 ejector by exploiting differences in head morphology between foxes and large dasyurids
Authors: Nicholson Evelyn , Gigliotti Frank
Published: December 2005

The M-44 ejector (ejector) is a more target-specific means of lethal control of red foxes (Vulpes vulpes) than conventional meat baits, which may expose a wide range of non-target species to the bait toxicant. Owing to the threshold pulling force required to activate the ejector, undesired exposure is eliminated in many smaller animals that cannot generate this force. However, the spotted-tailed quoll (Dasyurus maculatus) and the Tasmanian devil (Sarcophilus harrisii) remain potential non-target species because of their larger size. In this study, we report on the development of a collar that excludes devils and quolls by exploiting differences in their head morphology relative to that of red foxes. The collar potentially prevents bait removal by larger non-target species, while still allowing all adult foxes access to the bait to trigger the ejector mechanism. Spotted-tailed quolls small enough to access the bait are theoretically too small to trigger the ejector mechanism set at a threshold pulling force of 2.7 kg.
Loss of the limbic mineralocorticoid receptor impairs behavioral plasticity
Authors: Berger Stefan , Wolfer David P. , Selbach Oliver , Alter Heike , Erdmann Gitta , Reichardt Holger M. , Chepkova Aisa N. , Welzl Hans , Haas Helmut L. , Lipp Hans-Peter , Schütz Günther
Published: December 2005

Corticosteroid action in the brain is mediated by the mineralocorticoid (MR) and the glucocorticoid (GR) receptor. Disturbances in MR- and GR-mediated effects are thought to impair cognition, behavior, and endocrine control. To assess the function of the limbic MR in these processes, we inactivated the MR gene in the forebrain of the mouse using the Cre/loxP-recombination system. We screened the mice with a limbic MR deficiency in various learning and exploration tests. The mutant mice show impaired learning of the water-maze task and deficits in measures of working memory on the radial maze due to behavioral perseverance and stereotypy. They exhibit a hyperreactivity toward a novel object but normal anxiety-like behavior. The behavioral changes are associated with abnormalities of the mossy fiber projection and an up-regulation of GR expression in the hippocampus. Adult mutant mice show normal corticosterone levels at circadian trough and peak. This genetic model provides important information about the consequences of a permanently altered balance between limbic MR and GR, with implications for stress-related neuroendocrine and neuropsychiatric diseases.
Deregulation of common genes by c-Myc and its direct target, MT-MC1
Authors: Rogulski Kenneth R. , Cohen Debra E. , Corcoran David L. , Benos Panayiotis V. , Prochownik Edward V.
Published: December 2005

In addition to its role in cancer, the c-Myc oncoprotein controls many normal cellular processes as a consequence of its function as a basic helix–loop–helix leucine zipper transcription factor. Determining which of the myriad genes under c-Myc control are relevant for these various roles is thus a major challenge.
mt-mc1
is a direct c-Myc target gene whose overexpression recapitulates multiple c-Myc phenotypes, including transformation. Using transcriptional profiling, we now show that MT-MC1-overexpressing myeloid cells misregulate a total of 47 distinct transcripts, a large proportion of which are involved in signal transduction and/or cancer. Analysis of these genes reveals a consensus promoter structure consisting of multiple, often closely spaced c-Myc binding sites and three additional Wilm's tumor and Egr1-like motifs. More than one-third of MT-MC1 target genes are also clustered on six cancer-associated chromosomal loci. Most surprisingly, all of the transcripts examined also are regulated by c-Myc. Finally, an estrogen receptor–MT-MC1 fusion protein was used to establish that all examined transcripts were regulated directly by the chimeric protein. Our results thus indicate that MT-MC1 target genes largely comprise a subset of those regulated by c-Myc. We propose that the properties imparted by MT-MC1 are the result of its control of a small and select c-Myc target gene population.
Placing confidence limits on the molecular age of the human–chimpanzee divergence
Authors: Kumar Sudhir , Filipski Alan , Swarna Vinod , Walker Alan , Hedges S. Blair
Published: December 2005

Molecular clocks have been used to date the divergence of humans and chimpanzees for nearly four decades. Nonetheless, this date and its confidence interval remain to be firmly established. In an effort to generate a genomic view of the human–chimpanzee divergence, we have analyzed 167 nuclear protein-coding genes and built a reliable confidence interval around the calculated time by applying a multifactor bootstrap-resampling approach. Bayesian and maximum likelihood analyses of neutral DNA substitutions show that the human–chimpanzee divergence is close to 20% of the ape–Old World monkey (OWM) divergence. Therefore, the generally accepted range of 23.8–35 millions of years ago for the ape–OWM divergence yields a range of 4.98–7.02 millions of years ago for human–chimpanzee divergence. Thus, the older time estimates for the human–chimpanzee divergence, from molecular and paleontological studies, are unlikely to be correct. For a given the ape–OWM divergence time, the 95% confidence interval of the human–chimpanzee divergence ranges from –12% to 19% of the estimated time. Computer simulations suggest that the 95% confidence intervals obtained by using a multifactor bootstrap-resampling approach contain the true value with >95% probability, whether deviations from the molecular clock are random or correlated among lineages. Analyses revealed that the use of amino acid sequence differences is not optimal for dating human–chimpanzee divergence and that the inclusion of additional genes is unlikely to narrow the confidence interval significantly. We conclude that tests of hypotheses about the timing of human–chimpanzee divergence demand more precise fossil-based calibrations.
Socio‐scientific issues and the quality of exploratory talk—what can be learned from schools involved in a ‘collapsed day’ project?
Authors: Harris Richard , Ratcliffe Mary
Published: December 2005

This project was designed to examine the feasibility of using a ‘collapsed day’ to explore socio‐scientific issues relating to genes and genetic engineering in secondary schools by enabling science and humanities staff to collaborate. It was believed that science staff would have expertise in promoting understanding of genetics and humanities staff would have expertise in managing the ethical debates that emerged. The study took place in eight secondary schools with pupils aged 14–16. A surprising result of the project was the lack of high quality ‘public discourse’ or ‘exploratory talk’ around the ethical dilemmas raised by the topic. An examination of the data suggests that clarity about the nature of the day, teacher expertise in motivating and managing discussion, and pupil experience of discussion might be related to the level of discourse seen.
Formative assessment for all: a whole‐school approach to pedagogic change
Authors: Priestley Mark , Sime Daniela
Published: December 2005

Scotland's Assessment is for Learning initiative (AifL) seeks to introduce a co‐ordinated national system for assessment in schools. Formative assessment is a major plank in this. The initiative has moved beyond its pilot phase and it is intended that it will be adopted by all Scottish schools by 2007. This article draws upon the case‐study of a primary school that has adopted a whole‐school approach to enacting the formative assessment principles of AifL since 2004. It utilizes Margaret Archer's social theory to analyse and explain the processes of change that have underpinned the development of formative assessment in the school. The article argues that meaningful change in schools can be stimulated by encouraging socio‐cultural interaction among practitioners, via the impetus provided by a central initiative combined with the creation of spaces for dialogue and the extension of professional trust and autonomy.
Youth alcohol and other drug use in the United States and Australia: a cross‐national comparison of three state‐wide samples
Authors: TOUMBOUROU J. W. , BEYERS J. M. , CATALANO R. F. , HAWKINS J. D. , ARTHUR M. W. , EVANS‐WHIPP T. , BOND L. , PATTON G. C.
Published: December 2005

Although youth drug and alcohol harm minimization policies in Australia are often contrasted with the abstinence and zero tolerance policies adopted in the United States, there has been little research directly comparing youth substance use behaviour in the two countries. Three state representative samples in Victoria, Australia (n = 7898) and in the US states of Oregon (n = 15 224) and Maine (n = 16 245) completed a common cross‐sectional student survey. Rates of alcohol use (lifetime alcohol use, recent use in the past 30 days), alcohol use exceeding recommended consumption limits (binge drinking: five or more drinks in a session), other licit drug use (tobacco use), and norm‐violating substance use (substance use at school, use in the past 30 days of marijuana or other illicit drug use) were compared for males and females at ages 12–17. Rates were lower (odds ratios 0.5‐0.8) for youth in Maine and Oregon compared to Victoria for lifetime and recent alcohol use, binge drinking and daily cigarette smoking. However, rates of recent marijuana use and recent use of other illicit drugs were higher in Maine and Oregon, as were reports of being drunk or high at school. In contradiction of harm minimization objectives, Victoria, relative to the US states of Oregon and Maine, demonstrated higher rates of alcohol use exceeding recommended consumption limits and daily tobacco use. However, findings suggested that aspects of norm‐violating substance use (substance use at school, marijuana use and other illicit drug use) were higher in the US states compared to Victoria.