bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of N′4‐[11C]methyl‐ciprofloxacin for positron emission tomography studies
Authors: Goethals Patrick , Volkaert Anneke
Published: January 2005

The synthesis of N′4‐[11C]methyl‐ciprofloxacin for pharmacological studies using positron emission tomography is described. The starting material was treated with [11C]methyl iodide at 120°C in DMF for 5 min. After HPLC separation on a C18‐column with water/ethanol as mobile phase, the [11C]methyl labelled compound was produced with a radiochemical yield of at least 25% (end of synthesis from [11C]CO2). Activities from 1.48 to 2.22 GBq (40 to 60 mCi) were obtained 1 h after the irradiation, ready for intravenous injection. The carrier ranged between 0.05 and 0.08 μmol (0.010–0.016 μmol/ml). Copyright © 2002 John Wiley & Sons, Ltd.
11C labelling of AG957—a potential tyrphostin radiotracer for PET
Authors: Ackermann Uwe , Tochon‐Danguy Henri J. , Young Kenneth , Sachinidis John I. , Gordon Chan J. , Scott Andrew M.
Published: January 2005

Carbon‐11 labelled 4‐(N‐2,5‐dihydroxybenzyl)amino methyl benzoate (AG957), a potential radiotracer for imaging bcr–abl receptors was synthesized. [11C]AG957 was prepared by labelling 4‐aminobenzoic acid using [11C]CH3I, which affords the corresponding [11C] methyl ester in excellent yields. Subsequent condensation of the amino group with 2,5‐dihydroxy‐benzaldehyde formed the respective Schiff base. Reduction of this compound with NaBH3CN gave [11C]AG957 in overall decay corrected radiochemical yield of 65–75% (based on 11CH3I) with an average specific radioactivity of 40 GBq/μmol (1.1 Ci/μmol). The total synthesis time from EOB including formulation was 45 min. At physiological pH, the compound was found to be sufficiently stable for in vitro and in vivo investigations. Copyright © 2002 John Wiley & Sons, Ltd.
C‐Terminal 18F‐fluoroethylamidation exemplified on [Gly‐OH9] oxytocin
Authors: Jelinski M. , Hamacher K. , Coenen H. H.
Published: January 2005

The no‐carrier‐added (n.c.a.) 18F‐fluoroethylamidation of the acid function of the protected nonapeptide Boc–Cys–Tyr(tBu)–Ile–Gln(Mtt)–Asn(Mtt)–Cys–Pro–Leu–Gly–OH forming the labelled peptide hormone derivative [Gly‐(2‐[18F]fluoroethyl)NH9]‐oxytocin is described. The labelling conditions were elaborated using a protected tripeptide, identical to the C‐terminal sequence of oxytocin. The prosthetic group n.c.a. 2‐[18F]fluoroethylamine was synthesised via cryptate mediated n.c.a. 18F‐fluorination of N‐Boc‐2‐(p‐toluenesulfonyloxy)ethylamine in DMSO (RCY: ca. 60%) and subsequent deprotection with a radiochemical yield of 46±5%. [18F]Fluoroethylamine was reacted with Z–Pro–Leu–Gly–OH in presence of the coupling reagent TBTU or with activated esters of the model‐tripeptide. The activated ester method as well as the condensation in presence of TBTU yielded ⩾90% of the 18F‐fluoroethyl‐amidated tripeptide. TBTU‐mediated condensation of n.c.a. 2‐[18F]fluoro‐ethylamine with the C‐terminal free acid group of protected oxytocin gave the radiochemical yield of about 75%. Deprotection under acidic conditions led to the formation of [Gly–(2‐[18F]fluoroethyl)NH9]oxytocin within 75 min with a radiochemical yield of about 30% as measured by analytical HPLC. Copyright © 2002 John Wiley & Sons, Ltd.
Solid phase preparations of 99mTc labeled radiopharmaceuticals
Authors: Rao Ponugoti S. , Li Hongyu , Reddy Kishan C. , Thakur Mathew L.
Published: January 2005

For the preparation of most 99mTc radiopharmaceuticals, SnCl2 has remained the agent of choice for reduction of Tc7+ to lower valency states, which facilitates its chelation by compounds of diagnostic importance. We have developed a simple technique in which SnCl2 lyophilized in a glass vial, either alone or on a solid matrix of polymeric microspheres (beads), was used. Tin‐113 (t1/2 – 115 d) was used as a tracer, which facilitated quantitative assessment of loss or release of tin in the reaction mixtures. The feasibility and efficacy of this technique were examined for preparations of four 99mTc‐ labeled peptides, in which SnCl2 was used as a reducing agent for radiolabeling, a procedure well established in our laboratory. Labeling efficiencies for all four peptides using SnCl2 on solid phase was greater than 95%, as compared to less than 90% (P=0.05) for SnCl2 lyophilized without the solid matrix. Colloid formation was less than 3% in either case. The stability of SnCl2 was greater than six months for solid matrix, and less for that without the microspheres. The 113Sn measured as a daughter product 113mIn indicated that release of SnCl2 from microspheres in reaction mixture was 85±3%, as compared to 80±5% lyophilized alone. The recovery of 99mTc in solution from microspheres was 95–100%. The large size of the microspheres used (649 μm) eliminated the risk of drawing them through a needle in a syringe used for injection of a preparation. Copyright © 2002 John Wiley & Sons, Ltd.
Specific labelling of nucleosides and nucleotides with 13C and 15N
Authors: Milecki Jan
Published: January 2005

Synthetic methods leading to nucleosides and deoxynucleosides specifically labelled with 13C and 15N are reviewed. The paper covers labelling the sugar part of the molecule (with 13C) and the aglycone part (both with 13C and 15N). Synthetic methods for labelling at every relevant site of the nucleoside molecule are discussed. The paper also presents the strategies for the synthesis of multilabelled nucleosides. Copyright © 2002 John Wiley & Sons, Ltd.
Synthesis of selectively 15N‐ or 13C‐labelled malachite green
Authors: DeFina Steven C. , Dieckmann Thorsten
Published: January 2005

Two complimentary syntheses of selectively 15N‐ or 13C‐labelled malachite green hydrochloride were developed in order to provide labelled ligands for structural studies of RNA aptamer/ligand complexes. The 15N‐ and 13C‐labelled versions of the dye have been used in NMR studies to probe the changes in the electronic charge distribution and dynamics of the dye upon binding to RNA. Copyright © 2002 John Wiley & Sons, Ltd.
Microbiotic synthesis of 14C‐ringlabelled aminodinitrotoluenes (ADNT) and diaminonitrotoluenes (DANT)
Authors: Kröger Mario , Fels Gregor
Published: January 2005

The four 14C‐ringlabelled TNT‐metabolites 2‐aminodinitrotoluene (2‐ADNT), 4‐aminodinitrotoluene (4‐ADNT), 2,4‐diaminonitrotoluene (2,4‐DANT) and 2,6‐diaminonitrotoluene (2,6‐DANT) were synthesized in one step from TNT by reduction with baker's yeast (Saccharomyces cervisiae). Copyright © 2002 John Wiley & Sons, Ltd.
Synthesis of MMP inhibitor radiotracers [11C]methyl‐CGS 27023A and its analogs, new potential PET breast cancer imaging agents
Authors: Fei Xiangshu , Zheng Qi‐Huang , Hutchins Gary D. , Liu Xuan , Stone K. Lee , Carlson Kathy A. , Mock Bruce H. , Winkle Wendy L. , Glick‐Wilson Barbara E. , Miller Kathy D. , Fife Rose S. , Sledge George W. , Sun Hui Bin , Carr Raymond E.
Published: January 2005

[11C]Methyl‐CGS 27023A (1a) and its analogs [11C]methyl‐2‐picolyl‐CGS 27023A (1b), [11C]methyl‐benzyl‐CGS 27023A (1c), [11C]methyl‐2‐nitro‐CGS 27023A (1d), [11C]methyl‐3‐nitro‐CGS 27023A (1e), and [11C]methyl‐4‐nitro‐CGS 27023A (1f), novel radiolabeled matrix metalloproteinase (MMP) inhibitors, have been synthesized for evaluation as new potential positron emission tomography (PET) breast cancer imaging agents. The appropriate precursors for radiolabeling were obtained in four to five steps from starting material amino acid D‐valine with moderate to excellent chemical yields. Precursors were labeled by [11C]methyl triflate through 11C–O‐methylation method at the aminohydroxyl position under basic conditions and isolated by solid‐phase extraction (SPE) purification to produce pure target compounds in 40–60% radiochemical yields (decay corrected to end of bombardment), in 20–25 min synthesis time. Copyright © 2002 John Wiley & Sons, Ltd.
Labelled compounds of interest as antitumour agents – VIII. Synthesis of 2H‐isotopomers of pentamethylmelamine and of a potential prodrug thereof
Authors: Ferrer Sandra , Naughton Declan P. , Threadgill Michael D.
Published: January 2005

Treatment of 2‐chloro‐4,6‐(dimethylamino)‐1,3,5‐triazine with trideuteromethylamine gave 4,6‐(dimethylamino)‐2‐trideuteromethyl‐1,3,5‐triazine, an isotopomer of the experimental anticancer agent pentamethylmelamine (PMM). Mitsunobu coupling with 1,2‐dimethyl‐3‐hydroxymethyl‐5‐methoxy‐indole‐4,7‐dione gave 1,2‐dimethyl‐3‐(N‐(4,6‐bis(dimethylamino)‐1,3,5‐triazin‐2‐yl)‐N‐trideuteromethylaminomethyl)‐5‐methoxyindole‐4,7‐dione. This conjugate is a potential reductively triggered prodrug of PMM. Copyright © 2002 John Wiley & Sons, Ltd.
Radiohalogen incorporation into organic systems
Authors: Bolton R.
Published: January 2005

This Review reports the more recent applications of radiohalogen labelling in organic compounds. Modern synthetic methods place more emphasis upon substitution at specific sites. Electrophilic substitution, especially at aromatic carbon atoms, involves displacement of halogen or of metals rather than the earlier popular halogen‐deprotiation processes. Nucleophilic displacement, at either aliphatic or aromatic sites, has also become widespread since it may be made more selective by the inclusion of appropriate activating groups or suitable displaced groups. Microwave and thermally induced methods are both reported with a critical assessment of the value of each process. Copyright © 2002 John Wiley & Sons, Ltd.
Rapid microwave‐assisted cleavage of methyl phenyl ethers: new method for synthesizing desmethyl precursors and for removing protecting groups
Authors: Fredriksson Anna , Stone‐Elander Sharon
Published: January 2005

A new microwave‐enhanced method for rapid demethylation of methyl phenyl ethers using neat methanesulfonic acid (CH3SO3H) is presented. Using a monomodal microwave cavity, cleavage of anisole (1), used as model compound, to phenol (2) was achieved with high conversions (ca 80%) in very short reaction times (10–20 s). The feasibility of cleaving one or both of two methoxy groups was illustrated with 4‐(3‐bromoanilino)‐6,7‐dimethoxy‐quinazoline (PD153035, 3). High conversions (⩾82%) of 3 were attained with four different conditions (i.e. combination of input effect (35–125 W) and time (15 s–2 min)). 4‐(3‐Bromoanilino)‐7‐hydroxy‐6‐methoxyquinazoline (4), 4‐(3‐bromoanilino)‐6‐hydroxy‐7‐methoxyquinazoline (5) and 4‐(3‐bromoanilino)‐6,7‐dihydroxyquinazoline (6), the possible mono‐ or di‐demethylated compounds, were obtained. Methods for rapid demethylations are of interest in radiochemistry for post‐labeling deprotections of hydroxyl containing aromatic rings and also provide a more direct route for synthesizing precursor compounds for labeling by alkylation. Copyright © 2002 John Wiley & Sons, Ltd.
Src homology‐2 domain binding assays by scintillation proximity and surface plasmon resonance
Authors: Mandine Eliane , Gofflo Dominique , Jean‐Baptiste Véronique , Sarubbi Edoardo , Touyer Gaetan , Deprez Pierre , Lesuisse Dominique
Published: January 2005

Various SH2 competitive binding assays, based on different techniques, have been described in the literature to identify and characterize SH2 ligands. The consideration that most reported methods show experimental limitations associated with assay parameters has prompted us to base our Src‐SH2 inhibitor discovery program on the use of two different assays.
 In this study, two conceptually different biochemical methods designed to discover Src‐SH2 inhibitors, respectively scintillation proximity assay (SPA) and surface plasmon resonance (SPR), have been evaluated and compared. For its high sensitivity and adaptability to automation SPA was chosen for high capacity screening (primary screen), whereas SPR was used for hits confirmation (secondary screening). However with the drastic improvement of inhibitor affinities, the limit of sensitivity was rapidly reached for the SPR assay based on the canonical pYEEI ligand. The substitution of the natural, monophosphorylated peptide ligand with a triphosphorylated peptide has allowed us to remarkably increase its sensitivity, so that molecules with nanomolar affinities could be easily differentiated in terms of IC50 ranking. Such a new, improved SPR assay can be of great interest for the study of high affinity ligands of different SH2‐based drug targets. Copyright © 2001 John Wiley & Sons, Ltd.
NF‐κB pathway protects cochlear hair cells from aminoglycoside‐induced ototoxicity
Authors: Jiang Hongyan , Sha Su‐Hua , Schacht Jochen
Published: January 2005

Cell death in outer hair cells of the mammalian inner ear induced by aminoglycoside antibiotics is mediated by reactive oxygen species (ROS) and can be prevented by antioxidants. The current study investigates the role of the nuclear factor (NF)‐κB pathway in cell death or survival in adult CBA mice. Kanamycin (700 mg/kg subcutaneously, twice per day) progressively destroys hair cells but after 7 days of treatment auditory function and morphology are not yet affected significantly, permitting investigations of early events in drug‐induced cell death. Immunostaining for 4‐hydroxynonenal, indicative of lipid peroxidation, was elevated in the cochlea, but there was no effect on nitrotyrosine, a marker for peroxynitrite. NF‐κB was increased at 3 hr, 3 days, and 7 days of treatment, with p50 and p65 proteins as its most abundant subunits. Immunoreactivity for p50 was present in nuclei of inner hair cells and supporting cells that survive the drug treatment. In contrast, nuclei of outer hair cells were devoid of label. Concomitant injections of antioxidants, however, such as 2,3‐dihydroxybenzoic acid or salicylate (which prevent cell death induced by kanamycin), promoted the translocation of NF‐κB into the nuclei of outer hair cells. In addition, kanamycin treatment decreased tyrosine phosphorylation of the inhibitory IκBα protein, leading to increased IκBα levels in the cochlea; the effect was reversed by cotreatment with antioxidants. These results suggest that changes in the redox state of the cochlea stimulate the activation of NF‐κB and that this activation is cell protective. © 2005 Wiley‐Liss, Inc.
Schwann cells exhibit excitotoxicity consistent with release of NMDA receptor agonists
Authors: Wu Sheng‐Zhou , Jiang Shujun , Sims Terry J. , Barger Steven W.
Published: January 2005

Neurodegenerative effects of Schwann cells transplanted into the central nervous system have been observed previously. We report here that conditioned medium from Schwann cell cultures exhibit degenerative influences on hippocampal neurons. Aliquots of Schwann cell‐conditioned medium compromised the morphologic integrity of the neurons, markedly elevated their intracellular calcium concentrations, and decreased their viability. The degenerative effects of Schwann cell medium on neuronal morphology and viability were blocked by N‐methyl‐D‐aspartate (NMDA) receptor antagonists D‐(−)‐2‐amino‐5‐phosphonopentanoic acid (D‐APV) and 5,7‐dicholorokynurenic acid (DCKA). Glutamate was detected in Schwann cell‐conditioned medium at a concentration on the order of 10−5 M. D‐Amino acid oxidase (DAAOx) also attenuated the neurotoxicity exhibited by Schwann cells. These data suggest that Schwann cells release biologically relevant concentrations of excitotoxins that include glutamate and D‐serine. © 2005 Wiley‐Liss, Inc.
Identification and characterization of Caenorhabditis elegans palmitoyl protein thioesterase1
Authors: Porter Morwenna Y. , Turmaine Mark , Mole Sara E.
Published: January 2005

Infantile neuronal ceroid lipofuscinosis (INCL; Batten disease) is a severe neurodegenerative disorder of childhood characterized by the accumulation of autofluorescent storage material in lysosomes. It is caused by mutation of the CLN1/PPT1 gene, which encodes the lysosomal enzyme palmitoyl protein thioesterase‐1 (PPT1), but the mechanism of disease pathogenesis and substrates for the enzyme are unknown. Caenorhabditis elegans is a simple nematode worm, with a fully sequenced genome, which is easy to maintain and manipulate. It has a completely mapped cell lineage and nervous system and has already provided clues about the pathogenesis of several human neuronal and lysosomal storage disorders. We have identified and characterized a PPT1 homologue in C. elegans. We found that, although this gene was not essential for the animal's survival, its mutation resulted in a mild developmental and reproductive phenotype, affected the number and size of mitochondria, and resulted in an abnormality in mitochondrial morphology, possibly suggestive of a role for this organelle in INCL pathogenesis. This strain, deleted for ppt‐1, potentially provides a model system for the study of PPT1 and the pathogenesis of INCL. © 2005 Wiley‐Liss, Inc.
Loss of brain‐derived neurotrophic factor gene allele exacerbates brain monoamine deficiencies and increases stress abnormalities of serotonin transporter knockout mice
Authors: Ren‐Patterson Renee F. , Cochran Lauren W. , Holmes Andrew , Sherrill Suzanne , Huang Su‐Jan , Tolliver Teresa , Lesch Klaus‐Peter , Lu Bai , Murphy Dennis L.
Published: January 2005

To study the neurochemical and behavioral effects of altered brain‐derived neurotrophic factor (BDNF) expression on a brain serotonin system with diminished serotonin transport capability, a double‐mutant mouse model was developed by interbreeding serotonin transporter (SERT) knockout mice with BDNF heterozygous knockout mice (BDNF +/–), producing SERT –/– × BDNF +/– (sb) mice. Prior evidence implicates serotonin and SERT in anxiety and stress responses. Some studies have shown that BDNF supports serotonergic neuronal development, leading to our hypothesis that reduced BDNF availability during development might exaggerate the consequences of absent SERT function. In the present study, brain serotonin and 5‐hydroxyindol acetic acid concentrations in male sb mice were significantly reduced in the hippocampus and hypothalamus compared with wild‐type control SB mice, BDNF‐deficient Sb mice, and serotonin transporter knockout sB mice. The sb mice had significantly increased anxiety‐like behaviors compared with SB, Sb, and sB mice as measured on the elevated plus maze test. These sb mice also had significantly greater increases in plasma adrenocorticotrophic hormone than mice with other genotypes after a stressful stimulus. Analysis of neuronal morphology showed that hypothalamic and hippocampal neurons exhibited 25–30% reductions in dendrites in sb mice compared with SB control mice. These findings support the hypothesis that genetic changes in BDNF expression interact with serotonin and other circuits that modulate anxiety and stress‐related behaviors. Thus, this double‐mutant mouse model should prove valuable in studying other gene × gene consequences for brain plasticity as well as in evaluating epistatic interactions of BDNF and serotonin transporter gene polymorphisms in neuropsychiatric disorders. © 2005 Wiley‐Liss, Inc.
A renewal cluster model for the inter‐arrival times of rainfall events
Authors: Cowpertwait Paul S.P.
Published: January 2005

A statistical model, based on a renewal cluster point process, is proposed and used to infer the distributional properties of dry periods in a continuous‐time record. The model incorporates a mixed probability distribution in which inter‐arrival times are classified into two distinct types, representing cyclonic and anticyclonic weather. This results in rainfall events being clustered in time, and enables objective probabilistic statements to be made about storm properties, e.g. the expected number of events in a storm cluster. The model is fitted to data taken from a gauge near Wellington, New Zealand, by maximizing the likelihood function with respect to the parameters. The Akaike Information Criteria is used to select the best fitting distributions from a range of candidates. The Log‐Normal distribution is found to provide the best fit to the times between successive storm clusters, whilst the Weibull distribution is found to provide the best fit to the times between successive events in the same storm cluster. Harmonic curves are used to provide a parsimonious parameterization, allowing for the seasonal variation in precipitation. Under the fitted model, the interval series is transformed into a residual series, which is assessed to determine overall goodness‐of‐fit. Copyright © 2001 Royal Meteorological Society
Modelling low frequency variability in Southern Hemisphere extra‐tropical cyclone characteristics and its sensitivity to sea‐surface temperature
Authors: Reason C.J.C. , Murray R.J.
Published: January 2005

The outflow regions of the western boundary currents of the Southern Hemisphere and their extensions into the South Indian Ocean, South Pacific and South Atlantic Currents are prominent areas of low frequency variability in sea‐surface temperature (SST). One mechanism of decadal/multidecadal variability involves modulation of surface heat flux exchange and the track and intensity of extra‐tropical cyclones and associated frontal systems in response to a zonal mid‐latitude SST anomaly. Here, the influence of this type of SST pattern on cyclone properties is investigated by applying a vortex tracking scheme to atmospheric general circulation model integrations. In order to assess the subdecadal to multidecadal scale response, these integrations were conducted for a 21‐year period with forcing consisting of a warm SST anomaly stretching across the Southern Hemisphere mid‐latitudes.

In response to this forcing, a large‐scale trough at mid‐latitudes and ridging at higher latitudes are generated in the model. Associated with this change in Southern Hemisphere baroclinicity are increases in the density and flux of cyclonic systems in the 40°–55°S zone but decreases poleward of this latitude belt. It is found that the model response weakens throughout the Southern Hemisphere mid‐ to high‐latitudes in the second decade compared to the first but that there is less evidence of a hemispheric weakening in the second quinquennium relative to the first. Implications of these results for mechanisms of decadal/multidecadal climate variability are discussed. Copyright © 2001 Royal Meteorological Society.
Abrupt and sudden climatic transitions and fluctuations: a review
Authors: Lockwood J.G.
Published: January 2005

This review paper summarizes recent research work on abrupt climatic changes and oscillations. The climatic system is viewed as a dissipative, highly non‐linear system, under non‐equilibrium conditions, and, as such, should be expected to have some unusual properties. These unusual properties include bifurcation points with marked instability just before the point, magnification of semi‐periodic oscillations around bifurcation points, and variations in the strength of teleconnections with distance from equilibrium. These properties are discussed and illustrated for the climatic system using both the historical, Holocene and glacial climatic records. It is found that there are abrupt climatic changes and oscillations on all time‐scales. The amplitudes and frequencies of climate variability and teleconnections are found to vary between different time periods. A number of persistent oscillations exist, particularly one about 1500 years, but their amplitudes vary considerably between time periods. The Holocene appears to be no more climatically benign than the similar period in the Eemian. The importance of the North Atlantic thermohaline circulation for generating abrupt climatic changes in Europe, particularly in association with sudden pulses of fresh water, is illustrated. The concept of antiphase temperature changes between the North and South Atlantic is discussed. Externally generated abrupt climatic deteriorations owing to explosive volcanic eruptions and variations in solar irradiance are also discussed. Copyright © 2001 Royal Meteorological Society
Current approaches to seasonal to interannual climate predictions
Authors: Goddard L. , Mason S.J. , Zebiak S.E. , Ropelewski C.F. , Basher R. , Cane M.A.
Published: January 2005

This review paper presents an assessment of the current state of knowledge and capability in seasonal climate prediction at the end of the 20th century. The discussion covers the full range of issues involved in climate forecasting, including (1) the theory and empirical evidence for predictability; (2) predictions of surface boundary conditions, such as sea surface temperatures (SSTs) that drive the predictable part of the climate; (3) predictions of the climate; and (4) a brief consideration of the application of climate forecasts. Within this context, the research of the coming decades that seeks to address shortcomings in each area is described. Copyright © 2001 Royal Meteorological Society
Evolution of a periglacial landscape in the Late Devensian: environments and palaeobotany of the Mepal area, Cambridgeshire, England
Authors: West R. G. , Burton R. G. O. , Andrew R. , Pettit M. E.
Published: January 2005

The landscape evolution of the Mepal area from Late Devensian Block Fen Terrace times to the beginning of the Flandrian, a period of ca. 8000 radiocarbon years, is reconstructed. Stratigraphy is based on borehole transects and single boreholes, centred on a depression between the Block Fen Terrace and the Isle of Ely. Within the depression is a Devensian late‐glacial sequence, with the Windermere Interstadial represented by radiocarbon‐dated organic sediments. Pollen and plant macroscopic remains of the late‐glacial sediments are analysed. Plant communities with Betula developed in the interstadial. Before and after the interstadial there is much reworked pollen in the inorganic sediments, derived from local pre‐Devensian Pleistocene sediments, including temperate Ipswichian Stage sediments, and from mass‐wasting of the local Jurassic bedrock. Periods of such mass‐movement occur before and after the deposition of the late‐glacial lake sediments. Deposition of aeolian sediment occurs later than the main period of mass movement, but before the Windermere Interstadial. The relationship of the aeolian sediments in time and space to permafrost, indicated by local contraction polygons and cracks, is discussed. Solifluction diverted the flow of the River Great Ouse from a northeast direction in Block Fen Terrace times to a southwest direction as a channel developed to the west of the Chatteris–March ‘island’. This led to a drainage divide in Flandrian times. Copyright © 2002 John Wiley & Sons, Ltd.
Stomatal evidence for a decline in atmospheric CO2 concentration during the Younger Dryas stadial: a comparison with Antarctic ice core records
Authors: Mcelwain J. C. , Mayle F. E. , Beerling D. J.
Published: January 2005

A recent high‐resolution record of Late‐glacial CO2 change from Dome Concordia in Antarctica reveals a trend of increasing CO2 across the Younger Dryas stadial (GS‐1). These results are in good agreement with previous Antarctic ice‐core records. However, they contrast markedly with a proxy CO2 record based on the stomatal approach to CO2 reconstruction, which records a ca. 70 ppm mean CO2 decline at the onset of GS‐1. To address these apparent discrepancies we tested the validity of the stomatal‐based CO2 reconstructions from Kråkenes by obtaining further proxy CO2 records based on a similar approach using fossil leaves from two independent lakes in Atlantic Canada. Our Late‐glacial CO2 reconstructions reveal an abrupt ca. 77 ppm decrease in atmospheric CO2 at the onset of the Younger Dryas stadial, which lagged climatic cooling by ca. 130 yr. Furthermore, the trends recorded in the most accurate high‐resolution ice‐core record of CO2, from Dome Concordia, can be reproduced from our stomatal‐based CO2 records, when time‐averaged by the mean age distribution of air contained within Dome Concordia ice (200 to 550 yr). If correct, our results indicate an abrupt drawdown of atmospheric CO2 within two centuries at the onset of GS‐1, suggesting that some re‐evaluation of the behaviour of atmospheric CO2 sinks and sources during times of rapid climatic change, such as the Late‐glacial, may be required. Copyright © 2002 John Wiley & Sons, Ltd.
Monoclinic–orthorhombic phase transition in Ba2Cu(HCOO)6 crystals: a Raman scattering study
Authors: Paschoal C. W. A. , Ayala A. P. , Guedes I. , Freire P. T. C. , Melo F. E. A. , Mendes Filho J. , Leyva A. G. , Polla G. , Vega D. , Perazzo P. K.
Published: January 2005

The monoclinic–orthorhombic phase transition in Ba2Cu(HCOO)6 crystals, which takes place when the temperature is raised from 300 to 317 K, was analysed in the light of Raman scattering measurements. The disappearance of two modes related to HCOO vibrations is interpreted as the signature of phase transformation which is characterized by slight modifications in the atomic positions of HCOO in the unit cell. For the sake of completeness, we also show the evolution of the Raman spectrum from 50 to 300 K, where no phase transformation is observed. Copyright © 2002 John Wiley & Sons, Ltd.
Light and deuterated acetonitrile: an unresolved casus?
Authors: Morresi A. , Ombelli M. , Sassi P. , Santini S.
Published: January 2005

In spite of its high degree of symmetry and its simple structure, the physical and dynamic properties of acetonitrile are far from completely understood. In particular, the behaviour of deuterated acetonitrile does not follow the usual rules of isotopic substitution and consequently, it is not directly connected to the characteristics of the light molecule. Simple infrared and Raman experimental data on pure CH3CN and CD3CN together with isotopic and chemical equimolar mixtures the two are illustrated in detail; a qualitative interpretation is possible if it is accepted that the isotopic substitution can substantially modify the local organization of these molecular liquids. Copyright © 2002 John Wiley & Sons, Ltd.
Micro‐Raman study of iridium silicides
Authors: Almendra A. , Rodríguez A. , Rodríguez T. , Martín P. , Jiménez J.
Published: January 2005

The micro‐Raman spectra of three iridium silicides, IrSi, IrSi1.75 and IrSi3, were obtained. The silicides were prepared by rapid thermal annealing of iridium films deposited on Si substrates. The three phases were identified by Rutherford backscattering spectrometry. The main bands observed in the micro‐Raman spectra are described in order to provide a simple characterization method for these silicides with high spatial resolution. The three silicides present phonon bands around 165 and 200 cm−1. Some additional broad bands between 240 and 500 cm−1 were also observed. Copyright © 2002 John Wiley & Sons, Ltd.
Surface‐enhanced Raman scattering of imidazole adsorbed on an iron surface
Authors: Wang G. , Shi J. , Yang H. , Wu X. , Zhang Z. , Gu R. , Cao P.
Published: January 2005

The adsorption of imidazole on a roughened polycrystalline iron electrode was investigated by the SERS technique at pH values of neutral, 11 and 14 and compared with those from each solution. The results indicated that imidazole was adsorbed as mainly the neutral form and/or a certain amount of ylide form on the Fe surface in a neutral solution. The molecules have maximum adsorption at −0.9 V potential with tilted or perpendicular orientation with respect to the Fe surface, whereas a face‐on orientation of imidazole was favored at both more cathodic and anodic potentials. In a weaker basic solution imidazole was also adsorbed on the Fe surface as the neutral form, and took a face‐on orientation with respect to the Fe surface at all measured potentials because of its weaker adsorption than that in a neutral solution. Neutral and anionic forms of imidazole on the Fe surface were indicated by SERS at pH 14. Copyright © 2002 John Wiley & Sons, Ltd.
Spectroscopic and quantum‐control aspects of ultrashort‐pulse synthesis through impulsive high‐order stimulated Raman scattering
Authors: Zheltikov A. M.
Published: January 2005

The spectroscopic and quantum‐control aspects of short‐pulse synthesis through the generation of multiple Stokes and anti‐Stokes sidebands in an impulsively pre‐excited Raman‐active medium are considered. The use of sequences of short laser pulses leading to a resonant excitation of Raman modes is shown to allow the generation of multiple Stokes and anti‐Stokes sidebands to be considerably enhanced, with the characteristic length of the spectral broadening of a probe pulse propagating in a Raman‐active medium pre‐excited by a sequence of short pulses being inversely proportional to the number of pulses in this sequence. Coherent four‐wave mixing techniques are shown to be a convenient tool for visualizing the result of impulsive preparation of a Raman‐active medium. The results of Raman spectroscopic studies are used to specify Raman‐active molecules with sufficiently short periods of Raman vibrations and high efficiencies of Raman scattering, which offer especially much promise for the generation of few‐cycle light pulses in Raman‐active media. Copyright © 2002 John Wiley & Sons, Ltd.
Micro‐Raman scattering in Nb2O5–TiO2 ceramics
Authors: Dobal P. S. , Dixit A. , Katiyar R. S. , Choosuwan H. , Guo R. , Bhalla A. S.
Published: January 2005

Single‐phase (Nb2O5)1−x(TiO2)x ceramics were prepared for x = 0.00, 0.05, 0.08 and 0.11 compositions using a solid‐state reaction technique. The effect of TiO2 substitution on the vibrational and phase transition behavior of Nb2O5 was studied using the micro‐Raman scattering technique and compared with similar results on Ta2O5. The external modes resulting from interaction among various polyhedra were observed and vibrational changes were studied in the temperature range −200 to 1100°C. An increase in structural disorder was reflected in the Raman spectra with increasing TiO2 content in both Nb2O5 and Ta2O5. Ta2O5 shows a phase transition at about 300°C . However, a low‐temperature phase transition was observed about 50°C from (Nb2O5)1−x(TiO2)x compositions. Copyright © 2002 John Wiley & Sons, Ltd.
Polarized infrared and Raman spectra of KGd(WO4)2 and their interpretation based on normal coordinate analysis
Authors: Macalik L. , Hanuza J. , Kaminskii A. A.
Published: January 2005

The direction of the transition dipole moments for the vibrations of the single WOW and double WOOW oxygen bridges in layered scheelite tungstates is derived from the Polarized infrared and Raman spectra of the KGd(WO4)2 single crystal. Their experimental values are compared with those obtained from the calculated atomic Cartesian displacements for the particular normal modes. The assignment of the IR and Raman bands to the respective molecular vibrations was obtained on the basis of the normal coordinate analysis and potential energy distribution. Copyright © 2002 John Wiley & Sons, Ltd.
Raman spectra and thermal transformations of ferrihydrite and schwertmannite
Authors: Mazzetti L. , Thistlethwaite P. J.
Published: January 2005

Raman and infrared spectra of 2‐line and 6‐line ferrihydrite and schwertmannite were recorded. The spectra of the ferrihydrites are compatible with octahedrally coordinated Fe3+. The spectra of schwertmannite are consistent with Fe(O,OH)6 octahedra in some of which an OH− ion has been replaced by a SO42− ion which acts as a bridging bidentate ligand to two Fe3+ ions. The Raman spectra show that under heating by the He–Ne laser beam 2‐line ferrihydrite and schwertmannite transform to hematite via a maghemite intermediate, whereas 6‐line ferrihydrite transforms directly to hematite. The different thermal transformation behaviour of the two ferrihydrites accords with recent reports that the two forms are structurally different and suggests that it is the disordered component of 2‐line ferrihydrite that transforms to maghemite on heating. In the case of schwertmannite the loss on heating of SO42− ions in the form of SO3 and H2O entails the simultaneous loss of OH− ions and the conversion of some OH− ions to O2−. The loss and resulting rearrangement of ligands around those Fe3+ ions originally liganded by SO42− results in a fraction of Fe3+ achieving the tetrahedral coordination that is associated with maghemite. Copyright © 2002 John Wiley & Sons, Ltd.
Raman characterization of Ar+ ion‐implanted GaN
Authors: Boudart B. , Guhel Y. , Pesant J. C. , Dhamelincourt P. , Poisson M. A.
Published: January 2005

Ar+ ions were implanted at room temperature in n‐type hexagonal GaN for device isolation purpose. We performed electrical measurements and resonance Raman spectroscopy in order to monitor the electrical and structural changes of non‐annealed and annealed implanted GaN samples. On increasing the implantation dose from 3.4 × 1012 to 3.4 × 1014 ions cm−2, an increase in the electrical isolation and a decrease in the photoluminescence were observed. For a 1016 ions cm−2 dose, the implanted layer became conductive owing to a hopping mechanism and only the first‐order phonon lines remained observable. After annealing at 900 °C for 30 s, the implanted samples became conductive and the photoluminescence reappeared or increased compared with the non‐annealed samples at same implantation doses, except for the sample implanted at the highest dose, which became insulating. Copyright © 2002 John Wiley & Sons, Ltd.
The role of Government in the development of tourism in Kenya
Authors: Akama John S.
Published: January 2005

This study uses the case study of Kenya to analyse the role of government in the development of tourism in the Third World. Usually, government involvement in the development of tourism reflects on the uniqueness and peculiarity of the tourism industry. By its nature, the development and provision of tourism product involves diverse stakeholders and activities. In the diverse socio‐economic situation, it is usually the government that has the required social and political capacity and legitimacy to bring together and co‐ordinate the activities of diverse and different interest groups which are involved in the development of tourism and, also, establish the required level playing field. In this regard, as probably is the case in most less developed countries where tourism is a major socio‐economic activity, the Kenya Government has, over the years, played a crucial role in the development of the country's tourism industry. Particularly, during the exploratory stage of tourism development in Kenya, it was government involvement that helped lay the required groundwork and, as a consequence, jump‐started the rapid development of the country's tourism industry. However, in recent years, particularly in the 1990s, Kenya's tourism industry is confronted with serious problems including declining international visitor arrivals and decreasing tourism revenues. Ironically, the same government that played a crucial role, especially in the initial development of the country's tourism industry, is currently being blamed as being responsible for the industry's current poor performance. Thus, this study will also examine the underlying factors responsible for the current downturns in Kenya's tourism industry and how they relate to the role of government in the development of tourism. Copyright © 2002 John Wiley & Sons, Ltd.
Towards a classification of cultural tourists
Authors: McKercher Bob
Published: January 2005

This paper proposes a model to segment the cultural tourism market according to two dimensions: (i) the importance of cultural motives in the decision to visit a destination and (ii) depth of experience. The model is tested empirically using Hong Kong as a case study. The test identified five discrete cultural tourism market segments that exhibited substantially different behaviour. Copyright © 2002 John Wiley & Sons, Ltd.
Modes of e‐business innovation and structural disruptions in firm knowledge
Authors: Tiwana Amrit
Published: January 2005

This paper explores the linkages between knowledge integration strategy and the modes of innovation in architecturally destructive e‐business settings. Knowledge management (KM) is linked to the concepts of component and architectural knowledge in complex, global e‐business networks. Understanding the structural impact of incremental, radical, architectural, and modular innovations at the business model‐ and systems‐level on knowledge configurations can better guide KM strategy formulation. By delineating these linkages, this paper concludes with implications for managers of globalized teams and highlights open areas for future research. Copyright © 2002 John Wiley & Sons, Ltd.
Sustainability of livestock farming in the communal lands of Southern Namibia
Authors: Kuiper S. M. , Meadows M. E.
Published: January 2005

The impacts of livestock farming in southern Namibia's communal areas are investigated. Small stock farming is ubiquitous in this semiarid region, and provides many people with their only source of wealth and income. It is traditionally thought that livestock grazing negatively impacts on the vegetation resource. Using both interviews and interpretation of sequential aerial photographs, veld (a South African word descriptive of the general vegetation and soils within an area) resilience and changes in vegetation composition and cover were analysed. Results provide contrasting evidence. Resilience is illustrated by good plant regeneration after the 1999–2000 rainy season, an observation that provides support for a disequilibrium interpretation of the landscape, suggesting that productivity here is primarily event driven and not unduly impacted by grazing pressure. Additional, contradictory, results show that vegetation composition has indeed changed in the communal lands, from predominantly palatable perennials to unpalatable annuals. Localized areas of degradation are also evident. Using sequential aerial photography, comparison of land units under commercial tenure (1970) with the situation subsequent to incorporation into Namaland (1998) indicates an increase in bare soil from 6.3 to 11 per cent over the time period in question. This increase is attributed to, among other factors, increased pressure form livestock grazing. Although separating anthropogenic factors from other biophysical ones is difficult, it is argued that appropriate management practices should be employed that take into account both the veld's resilience and the observed localized degradation and species composition changes. Copyright © 2002 John Wiley & Sons, Ltd.
Carbon sequestration in dryland ecosystems of West Asia and North Africa
Authors: Lal R.
Published: January 2005

The West Asia–North Africa (WANA) region has a land area of 1.7 billion ha, and a population of 600 million. Desertification and soil degradation are severe problems in the region. The problem of drought stress is exacerbated by low and erratic rainfall and soils of limited available water holding capacity and soil organic carbon (SOC) content of less than 0.5 per cent. The SOC pool of most soils has been depleted by soil degradation and widespread use of subsistence and exploitative farming systems. The historic loss of a SOC pool for the soils of the WANA region may be 6–12 Pg compared with the global loss of 66–90 Pg. Assuming that 60 per cent of the historic loss can be resequestered, the total soil‐C sink capacity of the WANA region may be 3–7 Pg. This potential may be realized through adoption of measures to control desertification, restore degraded soils and ecosystems, and improve soil and crop management techniques that can enhance the SOC pool and improve soil quality. The strategies of soil‐C sequestration include integrated nutrient management (INM) and recycling, controlled grazing, and growing improved fodder species on rangeland. Improved technologies for cropland include use of INM and biofertilizers, appropriate tillage methods and residue management techniques, crop rotations and cover crops, and water and nutrient recycling technologies. Through adoption of such measures, the potential of soil‐C sequestration in the WANA region is 0.2–0.4 Pg C yr−1. Copyright © 2002 John Wiley & Sons, Ltd.
Rehabilitation of desurfaced soils by afforestation in La Plata County, Argentina
Authors: Giménez J. E. , Salerno M. I. , Hurtado M. A.
Published: January 2005

Removal of topsoil, mainly for making bricks, is one of the main causes of soil loss around large urban centres of the Humid Pampa, Argentina. In about 7 per cent of La Plata County, the 20–40 cm thick A‐horizon has been removed for that purpose. Most of the affected areas were originally prime farmland; however, with removal of the A‐horizon they became unsuitable for agriculture, including grazing, since the exposed Bt‐horizon is unsuited for plant growth due to its high clay content (45–65 per cent) and the low nutrient levels. Since trees survive better on poor soils than do agricultural crops, the possibility of afforestating desurfaced soils has been studied. Eucalyptus are one of the major species used in tree planting programmes aimed at reclaiming degraded soils since they are fast growing and can grow to commercial size in a wide range of soils and climatic conditions. The work reported here was done in a desurfaced Vertic Argiudoll and a similar non‐desurfaced soil (control). Three Eucalyptus species were tested, i.e. E. camaldulensis, E. viminalis and E. dunnii. Their height and diameter (dbh) growth were 47.9 to 75.8 per cent less and timber volume 86.5 to 98.5 per cent less on the desurfaced soil. E. camaldulensis grew best in all the parameters in the desurfaced soil. Although tree growth was poor, afforestation may be an alternative use for desurfaced soils where agriculture and livestock breeding are not possible. Copyright © 2002 John Wiley & Sons, Ltd.
Floodwater use and management strategies in valleys of southeast Spain
Authors: Hooke J. M. , Mant J.
Published: January 2005

Southeast Spain has a semiarid climate with highly variable rainfall from year to year. Global warming scenarios predict a decrease in rainfall in future and land‐use changes may also alter run‐off regimes. Water deficit has meant that various practices of floodwater farming have traditionally operated in valley floors. However, flash floods in the valley floors can also be dangerous and damaging. Many of the boqueras and other floodwater irrigation systems have been abandoned. The effects on the hydrological regime of the channel are calculated. These structures and water management practices could have an effect on the magnitude of low–moderate peak discharges, but are insignificant in high flows. Modern channel and flood management employs check dams, but these are frequently destroyed in moderate–high flows. Alternative strategies of channel management need to be sought and the use of vegetation cover to dissipate flood peaks and to reduce erosion may offer one possibility. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of chemical agent optical clearing potential using in vitro human skin
Authors: Choi Bernard , Tsu Laura , Chen Eric , Ishak Teresa S. , Iskandar Sarah M. , Chess Samuel , Nelson J. Stuart
Published: January 2005

Background and Objectives:

Optical clearing is a method that temporarily reduces the optical scattering of biological tissues.

Study Design/Materials and Methods:

To determine the optical clearing potential (OCP) of various chemical agents, we examined the change in reduced scattering coefficients of in vitro human skin after application directly to the dermal side.

Results/Conclusions:

We found that the mean agent OCP did not correlate with refractive index or osmolality. Lipophilic hyperosmotic agents had a mean OCP less than unity, indicating increased optical scattering. © 2005 Wiley‐Liss, Inc.