bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the toxic mechanism triggered by Alzheimer's amyloid‐β peptides via p75 neurotrophin receptor in neuronal hybrid cells
Authors: Tsukamoto Emi , Hashimoto Yuichi , Kanekura Kohsuke , Niikura Takako , Aiso Sadakazu , Nishimoto Ikuo
Published: August 2003

Neuronal pathology of the brain with Alzheimer's disease (AD) is characterized by numerous depositions of amyloid‐β peptides (Aβ). Aβ binding to the 75‐kDa neurotrophin receptor (p75NTR) causes neuronal cell death. Here we report that Aβ causes cell death in neuronal hybrid cells transfected with p75NTR, but not in nontransfected cells, and that p75NTRL401K cannot mediate Aβ neurotoxicity. We analyzed the cytotoxic pathway by transfecting pertussis toxin (PTX)‐resistant G protein α subunits in the presence of PTX and identified that Gαo, but not Gαi, proteins are involved in p75NTR‐mediated Aβ neurotoxicity. Further investigation suggested that Aβ neurotoxicity via p75NTR involved JNK, NADPH oxidase, and caspases‐9/3 and was inhibited by activity‐dependent neurotrophic factor, insulin‐like growth factor‐I, basic fibroblast growth factor, and Humanin, as observed in primary neuron cultures. Understanding the Aβ neurotoxic mechanism would contribute significantly to the development of anti‐AD therapies. © 2003 Wiley‐Liss, Inc.
Rapid increase of Nurr1 expression in the substantia nigra after 6‐hydroxydopamine lesion in the striatum of the rat
Authors: Ojeda Viviana , Fuentealba José Antonio , Galleguillos Danny , Andrés María Estela
Published: August 2003

Nurr1 is a transcription factor essential for the genesis of ventral dopaminergic neurons. In this study, we investigated the expression of Nurr1 protein and mRNA in the adult rat brain by using immunohistochemistry and in situ hybridization, respectively. Another aim of our study was to investigate Nurr1 expression in substantia nigra after dopamine depletion induced by the injection of 6‐hydroxydopamine in the striatum. We observed that Nurr1 mRNA and protein are expressed in several brain regions, including cortex, hippocampus, substantia nigra, and ventral tegmental area, in agreement with previous reports using in situ hybridization. Additionally, we found that Nurr1 is expressed in brain regions that have not been previously reported, such as striatum, septum, and superior colliculus. Highest levels of expression were found in cortex, medial septum, dentate gyrus, some hypothalamic nuclei, and substantia nigra. Interestingly, we observed that, in the superior colliculus, Nurr1 protein is localized in the cytoplasm of cells, whereas, in other regions, it was localized mainly in the nuclei, suggesting that Nurr1 subcellular localization is regulated and may have functional implications. Dopamine depletion induced by an injection of 6‐hydroxydopamine into the striatum produced an increase in the number of cells expressing Nurr1 mRNA and protein in both substantia nigra compacta and substantia nigra reticulata, ipsilateral and contralateral to the lesioned side, measured 24 hr after the 6‐hydroxydopamine injection. These results suggest that Nurr1 may be involved in many neuronal functions in the adult central nervous system and, in particular, might be related to the compensation processes that take place in dopaminergic cells in order to normalize extracellular dopamine levels in the striatum. © 2003 Wiley‐Liss, Inc.
Synergistic expression of inducible nitric oxide synthase by phorbol ester and interferon‐γ is mediated through NF‐κB and ERK in microglial cells
Authors: Han Inn‐Oc , Kim Hee‐Sun , Kim Hyoung‐Chun , Joe Eun‐Hye , Kim Won‐Ki
Published: August 2003

A proinflammatory cytokine IFN‐γ stimulates microglia in the injured brain; however, signaling pathways for IFN‐γ‐mediated microglia activation are not well characterized. In the present study, a protein kinase C (PKC) activator phorbol 12‐myristate 13‐acetate (PMA) acts in concert with IFN‐γ to enhance nitric oxide (NO) production in murine microglial BV2 cells by synergistically increasing expression of inducible NO synthase (iNOS). The synergistic NO production by PMA was in part decreased by a PKC inhibitor Gö6976. PMA alone induced activation of nuclear factor‐kappa B (NF‐κB) and extracellular signal‐regulated kinase (ERK) of mitogen‐activated protein kinases (MAPKs) subtypes, whereas IFN‐γ alone had little effect. PMA and IFN‐γ synergistically enhanced activity of NF‐κB, but not ERK. The inhibitors of NF‐κB (pyrrolidine dithiocarbamate, PDTC) and ERK (1,4‐diamino‐2,3‐dicyano‐1,4 bis[2‐aminophenylthio]butadiene; U0126) markedly decreased synergistic NO production in BV2 cells treated with IFN‐γ and PMA in combination. We found further that co‐treatment with IFN‐γ and PMA synergistically induced interferon regulatory factor‐1 (IRF‐1), which is the major transcription factor for IFN‐γ‐mediated iNOS expression. The present results demonstrate the cooperative interaction of multiple signaling pathways in the induction of NO production in activated microglial cells, and suggest that the functional interplay of these pathways may be important for the onset of microglia‐mediated inflammatory responses in brain. © 2003 Wiley‐Liss, Inc.
Relationships between cholinergic phenotype and acetyl‐CoA level in hybrid murine neuroblastoma cells of septal origin
Authors: Bielarczyk Hanna , Tomaszewicz Maria , Madziar Beata , Ćwikowska Justyna , Pawełczyk Tadeusz , Szutowicz Andrzej
Published: August 2003

High susceptibility of cholinergic neurons to neurotoxic signals may result from their utilization of acetyl‐CoA for both energy production and acetylcholine synthesis. SN56 cholinergic cells were transfected stably with cDNA for choline acetyltransferase. Transfected cells (SN56ChAT2) expressed choline acetyltransferase activity and acetylcholine content, 17 times and 2 times higher, respectively, than did nontransfected cells. Transfection did not change pyruvate dehydrogenase but decreased the acetyl‐CoA level by 62%. Differentiation by cAMP and retinoic acid caused an increase of choline acetyltransferase activity and decrease of acetyl‐CoA levels in both cell lines. Negative correlation was found between choline acetyltransferase activity and acetyl‐CoA level in these cells. SN56ChAT2 cells were more susceptible to excess NO than were native SN56 cells, as evidenced by the thiazolyl blue reduction assay. Thus, the sensitivity of cholinergic neurons to pathologic conditions may depend on the cholinergic phenotype‐dependent availability of acetyl‐CoA. © 2003 Wiley‐Liss, Inc.
Evidence for a second wave of oligodendrogenesis in the postnatal cerebral cortex of the mouse
Authors: Ivanova Anna , Nakahira Eiko , Kagawa Tetsushi , Oba Akio , Wada Tamaki , Takebayashi Hirohide , Spassky Nathalie , Levine Joel , Zalc Bernard , Ikenaka Kazuhiro
Published: August 2003

The existing view is that cortical oligodendrocytes (OLs) in rodents are born from the cortical subventricular zone (SVZ) after birth, but recent data suggest that many forebrain oligodendrocyte progenitor cells (OPCs) are specified much earlier (between E9.5 and E13.5 in the mouse) in the ventricular zone of the ventral forebrain under the control of sonic hedgehog (Shh) and migrate into the cortex afterward. We examined expression of specific early OL markers (PDGFRα, PLP/DM20, Olig2, and NG2) in the developing forebrain to clarify this issue. We propose that OPCs colonize the developing cortex in two temporally distinct waves. The gray matter is at least partially populated by a first wave of OPCs that arises in the medial ganglionic eminence and the entopeduncular area and spreads into the cortex via the developing cortical plate. The cerebral cortex benefits from the second wave of OPCs coming from residential SVZ. In the second wave, there might be two different types of precursor cells: PLP/DM20+ cells populating only inner layers and PDGFRα+ cells, which might eventually myelinate the outer regions as well. © 2003 Wiley‐Liss, Inc.
Differentiating work autonomy facets in a non‐Western context
Authors: Sadler‐Smith Eugene , El‐Kot Ghada , Leat Mike
Published: August 2003

Work autonomy is one important component of job design theory which in recent decades has been elaborated upon by a number of researchers who have argued that it may be disaggregated into separate work method, work schedule and work criterion autonomy facets. Breaugh (1985) developed the Work Autonomy Scales as measures of each of these. This article reports the results of two studies carried out in Egypt that explored the validity of Breaugh's scales in relation to job design theory. In Study 1, in which Breaugh's scales were administered to 534 employees in two large Egyptian organizations, the Work Autonomy Scales' three‐factor structure was verified using exploratory and confirmatory factor analyses. In Study 2, using a sample of 120 managers from four organizations, the associations between the three facets of work autonomy and other variables with which they would be expected to correlate, along with their relationships with a number of outcome variables, were explored. Statistically significant correlations were observed between certain of the work autonomy scales and task interdependence, Hackman and Oldham's autonomy scale and job complexity. In terms of outcomes, work schedule autonomy was associated with job commitment, while work criterion autonomy was associated with job satisfaction. The results are discussed in the light of previous findings and some suggestions for future research are offered. Copyright © 2003 John Wiley & Sons, Ltd.
Factor structure of the transformational leadership model in human service teams
Authors: Garman Andrew N. , Davis‐Lenane Deborah , Corrigan Patrick W.
Published: August 2003

The purpose of this study was to examine the factor structure of the transformational leadership model in human service teams. As the nature of this work environment mandates certain management‐by‐exception practices, patterns of correlations between perceptions of active and passive management‐by‐exception behaviors and transformational, transactional, and laissez‐faire leadership were of interest. 236 leaders and 620 subordinates from 54 mental health teams completed the Multifactor Leadership Questionnaire, form 8Y. Results suggest that active and passive management‐by‐exception factors are independent constructs. Copyright © 2003 John Wiley & Sons, Ltd.
Group absenteeism and positive affective tone: a longitudinal study
Authors: Mason Claire M. , Griffin Mark A.
Published: August 2003

This study investigates temporal variation in group absence behavior, and the relationship between group absenteeism and the group's positive affective tone. Absenteeism data were obtained from 97 work groups, aggregated over each of the four quarters of a year. The group's positive affective tone was measured through two employee opinion surveys. Multi‐level regression analyses were carried out, in which linear, quadratic, and cubic change trends were tested as predictors of change over time in group absenteeism. All three change trends explained unique variance in the group absenteeism data, indicating that the level of group absenteeism changes over time. We also found that there was significant variation between groups in the strength and direction of the linear and quadratic change trends. Positive affective tone was negatively related to the level of group absenteeism, and change in positive affective tone predicted the strength and direction of the linear change trend for group absenteeism. Copyright © 2003 John Wiley & Sons, Ltd.
Predictors of success in the era of the boundaryless career
Authors: Eby Lillian T. , Butts Marcus , Lockwood Angie
Published: August 2003

The present study examines three classes of career competencies proposed as important predictors of success in the boundaryless career. Three criteria of career success were examined: perceived career satisfaction, perceived internal marketability, and perceived external marketability. Using data from 458 alumni from a large southeastern university, predictions were tested using partial correlations and dominance analysis. The results found support for the importance of ‘knowing why,’ ‘knowing whom,’ and ‘knowing how’ as suggested by previous theoretical work. The findings are discussed in reference to future research and theorizing on the boundaryless career. Copyright © 2003 John Wiley & Sons, Ltd.
Firm reputation and applicant pool characteristics
Authors: Turban Daniel B. , Cable Daniel M.
Published: August 2003

Scholars have suggested that a firm's reputation can provide it with a competitive advantage by attracting more, and possibly higher‐caliber, applicants. No research has actually investigated this relationship, however, in large part because researchers have not assessed applicant pool characteristics but instead have measured applicants' intentions. Therefore, we conducted two studies to investigate whether organizational reputation influenced the number and the quality of applicants actually seeking positions with firms. Company reputation was operationalized using two different published reputation measures, and applicant quality data were obtained from career services offices at business schools at two universities. Results from both studies supported the previously untested belief that firms with better reputations attract more applicants. Furthermore, some evidence suggested that firms with better reputations could select higher‐quality applicants. Copyright © 2003 John Wiley & Sons, Ltd.
Why do lay people believe that satisfaction and performance are correlated? possible sources of a commonsense theory
Authors: Fisher Cynthia D.
Published: August 2003

Decades of research have shown that the correlation between job satisfaction and job performance is modest in magnitude, yet lay people are thought to believe strongly that satisfied or ‘happy’ employees are more productive at work. This paper first documents the strength and pervasiveness of belief in several versions of the happy–productive worker hypothesis (Study 1), then proposes and explores potential substantive explanations for these beliefs (Study 2). It is possible that lay people base their beliefs on genuinely stronger relationships that occur at a different level of analysis than usually studied by researchers, and/or that exist between satisfaction‐like and performance‐like variables other than the constructs typically investigated by scholars. Study 2 provides data relevant to several of these possibilities. The most compelling findings were at the within‐person level of analysis. The average within‐person correlation between momentary task satisfaction and concurrent perceived task performance was 0.57. Individuals feel more satisfied than usual when they believe they are performing better than usual for them. If lay persons mistakenly generalize from their own within‐person experiences of satisfaction–performance covariation to the between‐persons level, this relationship may be the basis for the strong lay belief that satisfied workers perform better. Copyright © 2003 John Wiley & Sons, Ltd.
Diversity and team outcomes: the moderating effects of outcome interdependence and group longevity and the mediating effect of reflexivity
Authors: Schippers Michaéla C. , Den Hartog Deanne N. , Koopman Paul L. , Wienk Janique A.
Published: August 2003

Reflexivity—the extent to which teams reflect upon and modify their functioning—has been identified as a possible key factor in the effectiveness of work teams. We examined the extent to which team composition affected team process (i.e., reflexivity) and in turn team outcomes (i.e., satisfaction, commitment, and performance). The results of diversity research thus far have been inconclusive in terms of positive or negative effects of team composition on team process and outcomes. In the current research, group longevity and outcome interdependence were expected to moderate the relationship between diversity on the one hand and reflexivity and team outcomes on the other hand. Reflexivity was expected to mediate these interaction effects. The current field study was conducted among 54 work teams from 13 different organizations. As predicted, few main effects were found. Instead, analyses showed interaction effects of diversity and outcome interdependence on the measures of reflexivity, satisfaction, and performance. As predicted, interaction effects were also found for diversity and group longevity on the measures of reflexivity, satisfaction, and performance. Three‐way interactions were found for satisfaction and commitment. Also, reflexivity was shown to mediate these relationships, indicating that the moderating effects of outcome interdependence and group longevity on the relation between diversity and team outcomes are due to the effects on process. Copyright © 2003 John Wiley & Sons, Ltd.
Tephrochronology and tephrostratigraphy of two Pleistocene continental fossiliferous successions from central Italy
Authors: Marcolini F. , Bigazzi G. , Bonadonna F. P. , Centamore E. , Cioni R. , Zanchetta G.
Published: August 2003

The stratigraphical context of two Middle Pleistocene fossiliferous palaeosols from Central Italy (Abruzzo and Tuscany) have been studied. Small mammals and molluscs occur in both palaeosols, which are covered by tephra layers that were analysed using an interdisciplinary approach. Application of fission‐track dating to apatites separated from the Case Picconetto tephra (Pescara, Abruzzo), yielded an age of 0.48 ± 0.04 Ma, indistinguishable from those previously determined for the Campani Quarry (Lower Valdarno, Tuscany) (0.46 ± 0.05 Ma and 0.48 ± 0.05 Ma). Geochemical and petrographic investigations indicate that these tephra originated from different volcanoes, the Alban Hills Volcanic Complex and the Vico Volcano (Latium) respectively. Small mammal and mollusc assemblages indicate different palaeoclimatic and palaeoenvironmental conditions for the Case Picconetto and Campani Quarry palaeosols. Warm and humid conditions can be inferred for the Campani Quarry site, whereas open and cold conditions can be inferred for Case Picconetto. On the basis of faunal data, fission‐track dates and attribution of tephra to specific volcanic eruptions, we suggest a correlation of these faunas with marine oxygen isotope stage 14 (Case Picconetto) and with marine oxygen isotope stage 11 (Campani Quarry), respectively. Copyright © 2003 John Wiley & Sons, Ltd.
A late Holocene record of arid events from the Cuzco region, Peru
Authors: Chepstow‐Lusty Alex , Frogley Michael R. , Bauer Brian S. , Bush Mark. B. , Herrera Alfredo Tupayachi
Published: August 2003

The small recently infilled lake basin of Marcacocha (13°13′S, 72°12′W, 3355 m) in the Cuzco region of Peru has a morphology and location that renders it extremely sensitive to environmental change. A record of vegetation, human impact and climatic change during the past 4200 yr has been obtained from a highly organic core taken from the centre of the basin. Sustained arid episodes that affected the Peruvian Andes may be detectable using the proxy indicator of sedge (Cyperaceae) pollen abundances. As the lake‐level was lowered during sustained drier conditions, the local catchment was colonised by Cyperaceae, whereas during lake floods, they retreated or were submerged and pollen production was correspondingly reduced. Drier episodes during prehistoric times occurred around 900 bc, 500 bc, ad 100 and ad 550, with a longer dry episode occurring from ad 900 to 1800. Evidence from the independently derived Quelccaya ice‐core record and the archaeological chronology for the Cuzco region appears to support the climatic inferences derived from the sedge data. Many of these aridity episodes appear to correspond with important cultural changes in the Cuzco region and elsewhere in the Central Andes. Copyright © 2003 John Wiley & Sons, Ltd.
High‐pressure metastable phase transitions in β‐Ge3N4 studied by Raman spectroscopy
Authors: McMillan Paul F. , Deb Sudip K. , Dong Jian‐Jung
Published: August 2003

We studied polymorphic transitions occurring in β‐Ge3N4 metastably compressed to high pressures (P = 40 GPa) at room temperature. Previous studies under high‐pressure–high‐temperature conditions have shown that this phase transforms into a newly discovered spinel‐structured material (γ‐Ge3N4) above 10 GPa and 1200°C. However, ab initio theoretical studies have indicated that the phenacite‐structured low‐pressure β‐Ge3N4 polymorph should also undergo a series of metastable transformations upon compression at low temperatures. Here we studied these transformations by in situ Raman spectroscopy in a diamond anvil cell. The phase transitions were first predicted to involve a sequence of second‐order phase changes driven by soft phonon modes at the Brillouin zone centre (the Γ point: q = 0) resulting in displacive motions of the N atoms, causing the symmetry to descend from P63/m through P6 to P3. The two transitions were predicted to occur at P = 20 and 28 GPa. However, it was also noted that a direct first‐order transition between P63/m and P3 phases might occur at P = 23 GPa if order–disorder processes or phonon condensations away from the Brillouin zone centre were considered. Here we present experimental evidence for a phase transition occurring at P = 20 GPa, within β‐Ge3N4 that has been metastably compressed at ambient temperature. From the number of Raman modes observed, this transition most likely corresponds to the direct P63/m–P3 transformation, and it is therefore first order in character, but with a small activation energy barrier as ascertained by little or no hysteresis observed upon decompression. However, when all the minor features appearing in the Raman spectrum are accounted for, the number of observed resonances is greater than the number of zone centre modes expected even for the P3 structure. This indicates that the true unit cell is larger than expected from zone‐centre mode softening, and that order–disorder processes or phonon instabilities at q≠0 must have occurred during the transition. Copyright © 2003 John Wiley & Sons, Ltd.
Raman scattering studies at high pressure and low temperature: technique and application to the piezoelectric material PbZr0.52Ti0.48O3
Authors: Haines J. , Rouquette J. , Bornand V. , Pintard M. , Papet Ph. , Gorelli F. A.
Published: August 2003

Raman spectroscopy is a powerful tool for the study of solids under extreme conditions of pressure and temperature. This technique can be used to determine phase diagrams and study phase transition mechanisms. Raman spectroscopy can be used to characterize disorder present in crystalline solids and is sensitive to local structural configurations. The combined use of diamond anvil cells and closed‐cycle helium cryostats enables Raman scattering experiments to be performed at pressures exceeding 50 GPa in the 10–300 K temperature range. The use of this technique to study the perovskite‐type piezoelectric material PbZr0.52Ti0.48O3 enables the monoclinic and cubic phases present in this system to be characterized and their pressure–temperature domains of stability to be defined. Raman scattering results indicate the presence of polar domains in the cubic, high‐pressure phase. The ferroelectric monoclinic phases exhibit extended stability at high pressure and low temperature. Copyright © 2003 John Wiley & Sons, Ltd.
High‐pressure phase transitions in tetrahedrally coordinated chain structures
Authors: Serghiou G.
Published: August 2003

We present an overview of phase transition trends and medium range order structural criteria proposed to dictate the transformation of chain silicates to either dense crystalline or amorphous phases at high pressures. These are based on Raman spectroscopic measurements of the tetrahedrally coordinated (SiO4) chain silicates MgSiO3, Ca0.5Mg0.5SiO3, CaSiO3 and MnSiO3 and of octahedrally coordinated (SiO6) MgSiO3 ilmenite to 70 GPa. The tetrahedrally coordinated structures either become amorphous or transform to dense crystalline phases upon compression, depending on the sequencing of their building blocks (labeled P and C modules). Chain silicates containing only P modules transform to dense crystalline phases whereas chain silicates containing a sequence of P and C modules become amorphous, and those containing only C modules exhibit both crystalline and amorphous regions. Based on a comparison with the high‐pressure Raman spectra of octahedrally coordinated (SiO6) ilmenite MgSiO3, the dense metastable high pressure crystalline Ca0.5Mg0.5SiO3, MgSiO3 and CaSiO3 phases also contain SiO6 units. Copyright © 2003 John Wiley & Sons, Ltd.
In situ Raman monitoring of the growth of CVD diamond films
Authors: Mermoux M. , Marcus B. , Abello L. , Rosman N. , Lucazeau G.
Published: August 2003

Raman spectroscopy was applied to monitor the growth of diamond in different plasma‐assisted chemical vapour deposition reactors. A gated, multichannel detection system was used to discriminate against the high level of background radiation produced by the plasma and the hot substrate. As a result, Raman spectra could be taken during diamond growth without interruption of the process. The ability to detect and distinguish between diamond and non‐diamond phases during film growth is demonstrated. A sufficient signal‐to‐noise ratio in the spectra was achieved for stress formation to be observed. Copyright © 2003 John Wiley & Sons, Ltd.
High temperatures and Raman scattering through pulsed spectroscopy and CCD detection
Authors: Simon P. , Moulin B. , Buixaderas E. , Raimboux N. , Herault E. , Chazallon B. , Cattey H. , Magneron N. , Oswalt J. , Hocrelle D.
Published: August 2003

A Raman scattering system devoted to high temperatures is presented. It is based on a pulsed system to remove thermal emission with retaining charge‐coupled device (CCD) detection. Two types of optical gating are used: a Pockels switch or an intensified CCD (ICCD), combining in this case the optical gate and the CCD detection. The performances of both systems are presented and their respective advantages are discussed and compared. The ICCD device allows recording of spectra in the 2000°C range, and typical results obtained on alumina and zirconia ceramics are shown. Copyright © 2003 John Wiley & Sons, Ltd.
High‐pressure polymerization of phenylacetylene and of the benzene and acetylene moieties
Authors: Santoro Mario , Ciabini Lucia , Bini Roberto , Schettino Vincenzo
Published: August 2003

The reactivity induced in acetylene, benzene and phenylacetylene crystals by the application of high external pressure is discussed. Acetylene, the simplest model system involving the CC triple bond, reacts above 3.0 GPa in the orthorhombic crystal phase. The molecular arrangement in this phase determines the final conformation of the recovered polymer. The role of laser irradiation in branching the polyenic chains, through the dissociation of the double bonds, is revealed. Benzene, the model aromatic molecule, starts to react in the solid state above 23 GPa. A progressive distortion of the rings is observed on increasing pressure up to 50 GPa but the transformation becomes complete, close to ambient pressure, only during the decompression run. An amorphous hydrogenated carbon compound (a‐C:H) is formed in this reaction. Laser irradiation with suitable wavelengths reduces the reaction pressure threshold revealing the role of the S1 excited state in driving the high‐pressure reaction. Finally, phenylacetylene was taken into account since it is the simplest molecule involving both the triple bond and the aromatic ring and its reactivity could be possibly interpreted according to the previous model systems. Phenylacetylene starts to react in the solid state above 8 GPa. The reaction mainly involves the triple bond of the ethynyl fragment forming polyphenylacetylenic chains. On the basis of the infrared spectra a possible polymer structure is proposed. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of pressure and temperature on Raman spectra of solids: anharmonicity
Authors: Lucazeau Guy
Published: August 2003

This paper gives a brief review of the effect of temperature and pressure on Raman spectra. Anharmonicity, defined by the cubic, quartic and higher terms in the potential expansion, is shown to be responsible for various properties such as dilatation or for variations of wavenumber and half‐width of Raman bands with temperature and pressure, or may be strongly involved in phase transitions. This contribution does not pretend to be an exhaustive review on the subject but aims to introduce some basic concepts in a tutorial way before showing how intricated are these manifestations of anharmonicity. Copyright © 2003 John Wiley & Sons, Ltd.
Raman spectroscopy of metals, high‐temperature superconductors and related materials under high pressure
Authors: Goncharov Alexander F. , Struzhkin Viktor V.
Published: August 2003

An overview is presented of recent Raman scattering measurements in metals under conditions of high static pressure in the diamond anvil cell. Also discussed are the practical improvements of the traditional technique that have made these measurements possible. We present the results of several studies including those of hexagonal close‐packed (hcp) ε‐Fe and its solid solutions Fe(1−x)Nix (x ≤ 0.2) over a wide temperature range, and also of high‐temperature superconductors (YBCO) and their prototypes, i.e. materials with strong electronic correlations such as the 3d metal oxides CoO and FeO. Copyright © 2003 John Wiley & Sons, Ltd.
Brillouin scattering at high pressure: an overview
Authors: Polian Alain
Published: August 2003

Brillouin scattering allows the determination of acoustic velocities and adiabatic elastic moduli in matter. These data are crucial in many areas of science, such as fundamental physics, geosciences and technology, especially when measured as a function of the density (pressure). In this paper, we present a review of the work performed on Brillouin scattering under high pressure in diamond anvil cells, emphasizing the most recent results. Copyright © 2003 John Wiley & Sons, Ltd.
High‐pressure Raman spectroscopy of nano‐structured ABO3 perovskites: a case study of relaxor ferroelectrics
Authors: Kreisel J. , Bouvier P.
Published: August 2003

A large number of outstanding physical properties observed in perovskite‐type oxides, such as giant piezoelectricity, colossal magneto‐resistance and high‐Tc superconductivity, are related to an intrinsic nano‐scaled local structure. For instance, the presence of a nano‐scaled structure is characteristic of so‐called relaxor ferroelectrics (relaxors), which have attracted considerable attention since the recent discovery of ultra‐high strain and giant piezoelectric properties. In this paper we review, through a case study of relaxors, how the combination of the external parameter high‐pressure and Raman spectroscopy allows an instructive investigation of nano‐scaled perovskites, which is often at best a difficult task for conventional ‘average‐structure’ techniques such as diffraction. We show that perovskite‐type relaxors present important pressure instabilities with respect to both cation sizes and we suggest that the latter instabilities might well be at the origin of the reduced dielectric performances that are observed for strained thin‐film relaxors. Finally, we briefly illustrate how the approach might be used for nano‐scaled manganite‐type oxides. Copyright © 2003 John Wiley & Sons, Ltd.
Status of phonon studies at high pressure by inelastic x‐ray scattering
Authors: Krisch Michael
Published: August 2003

A representative selection of high‐pressure inelastic x‐ray scattering experiments are described and future perspectives for this relatively new technique are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Raman spectroscopy as a probe for in situ studies of pressure‐induced amorphization: some illustrative examples
Authors: Pereira A. S. , Perottoni C. A. , da Jornada J. A. H.
Published: August 2003

The main models proposed in the literature to describe pressure‐induced amorphization (PIA) are briefly reviewed, with special emphasis on the kinetic aspects of PIA. The high potential of Raman spectroscopy for experimental studies on PIA is highlighted and illustrated by the results obtained for zirconium tungstate (ZrW2O8) and boric acid (H3BO3). Compared with x‐ray diffraction using a conventional x‐ray tube, Raman spectroscopy allowed a much faster identification of the transitions in both compounds. Further, the Raman results for ZrW2O8 have given support to an amorphization mechanism based on the freezing of low‐energy vibrational modes associated with rigid (or quasi‐rigid) ZrO6 and WO4 polyhedral units. For H3BO3, we obtained strong evidence of a PIA associated with hindered decomposition of H3BO3, probably to a mixture of HBO2 and H2O. The short acquisition time for the Raman measurements of samples under high pressure enabled us to follow the kinetics of the transition on H3BO3, which could hardly be done by conventional x‐ray diffraction. Raman spectroscopy proved to be a very convenient technique to study the mechanisms behind PIA, owing not only to the fast acquisition of information about phase transition kinetics, but also to the structural information that can be obtained. Copyright © 2003 John Wiley & Sons, Ltd.
Raman spectroscopy on carbon nanotubes at high pressure
Authors: Loa I.
Published: August 2003

Raman spectroscopy has been the most extensively employed method to study carbon nanotubes at high pressures. This review covers reversible pressure‐induced changes of the lattice dynamics and structure of single‐ and multi‐wall carbon nanotubes and irreversible transformations induced by high pressures. The interplay of covalent and van der Waals bonding in single‐wall nanotube bundles and a structural distortion near 2 GPa are discussed in detail. Attempts to transform carbon nanotubes into diamond and other ‘superhard’ phases are reviewed critically. Copyright © 2003 John Wiley & Sons, Ltd.
Phase diagram of ice in the VII–VIII–X domain. Vibrational and structural data for strongly compressed ice VIII
Authors: Pruzan Ph. , Chervin J. C. , Wolanin E. , Canny B. , Gauthier M. , Hanfland M.
Published: August 2003

The first part of this paper presents a short survey on the phase diagram of ice in the pressure range from 2 to 100 GPa from 10 to 300 K. The description is mainly devoted to the problem of the symmetrization of the O—H· · ·O bond, that is, the transformation of ice VII or VIII to ice X. In connection with this introduction, in the second part of the paper new vibrational and structural data obtained from Raman scattering and x‐ray diffraction in ice VIII are given and these properties are compared with those of ice VII. Specifically, below 100 K, solid VIII vanishes at 62 GPa to give birth to a state which is the first step to ice X. This transition is marked by a softening of the lowest Raman‐active lattice mode and the disappearance of the Raman signal. During the compression of ice VIII the O–H stretching mode wavenumber shows soft mode behaviour. It is found that the expansivity of ice VIII is negative above 10 GPa. Copyright © 2003 John Wiley & Sons, Ltd.
High‐pressure antiferromagnetic phases of solid oxygen
Authors: Gorelli F. A. , Santoro M.
Published: August 2003

We report on the antiferromagnetic character of solid oxygen in the high‐pressure, low‐temperature region enclosed between the β and ε phases. The occurrence of a first‐order phase transition, positioned at 5.5–6.5 GPa, between the monoclinic α (C2/m) and the orthorhombic δ (Fmmm) phases was shown by means of an accurate x‐ray diffraction analysis. The two crystal structures were assessed to be antiferromagnetically ordered, owing to a narrow peak observed in the IR spectrum and assigned to a vibron component. The absorption of this mode is allowed owing to the coupling of the molecular spins, which produces a doubling of the primitive cell. The vibrational coupling parameter was quantitatively related to the exchange integralJinvolved in the Heisenberg interaction. Finally, absorption measurements at different pressures of the electronic transition$^{3}\Sigma_{g}^{-} \rightarrow{}^{1}\Delta_{g}$, lying in the near‐IR spectral range, allowed us, by means of a simple model, to obtain directly the quantityJas a function of the nearest‐neighbour distance. Copyright © 2003 John Wiley & Sons, Ltd.
Megabar high‐pressure cells for Raman measurements
Authors: Eremets M. I.
Published: August 2003

Experimental aspects of Raman measurements at megabar pressures are considered. Features of diamond anvil cells working above 200 GPa are described. Problems of luminescence background at megabar pressures and the use of low‐luminescence diamonds are considered. Methods of pressure measurements at very high pressures are discussed. The pressure dependence of the Raman shift from the diamond anvil tip was used as a reliable estimate of the pressure. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of alkaloids in Ipecacuanhae radix and preparations by capillary zone electrophoresis
Authors: Sturm Sonja , Taglioli Vania , Bilia Anna R. , Vincieri Francesco , Stuppner Hermann
Published: August 2003

A capillary zone electrophoresis method for quantitation of the alkaloids emetine and cephaeline in Ipecacuanhae radix fluid extract and Ipecac syrup using papaverine as internal standard is described. Baseline separation was achieved within 10 min using a fused silica capillary and a running electrolyte consisting of citric acid (50 mM), disodium hydrogenphosphate (100 mM), and 2.5% methanol (pH 4.4). Regression equations revealed a linear response from 0.05 to 1.9 mg/mL for cephaeline and emetine (correlation coefficients 0.9991–0.9993). The lowest quantitation limits were determined as 0.03 mg/mL for both alkaloids, and the limit of detection was 0.012 mg/mL. The day‐to‐day variations of retention times were < 1.3% for both compounds. Whereas no sample pre‐treatment was necessary for analysis of the fluid extract, SPE had to be applied before CE analysis of the syrup. The recovery rate for emetine in this case was > 99.8%.
Study on the feasibility of coupling large‐volume injection to fast gas chromatography with mass spectrometric detection for analysis of organochlorine pesticides
Authors: Korenková Eva , Matisová Eva , Slobodník Jaroslav
Published: August 2003

A combined use of programmable temperature vaporisation injector, fast oven temperature ramp, 0.1 mm ID analytical column and hydrogen carrier gas enabled injection of up to 20 μL of extract containing 15 organochlorine pesticides and separation of all analytes in less than 8 minutes.
Comprehensive two‐dimensional gas chromatography (GC×GC) and GC×GC‐quadrupole MS analysis of Asian and American ginseng
Authors: Shellie Robert A. , Marriott Philip J. , Huie Carmen W.
Published: August 2003

Extracts of the roots of Panax (ginseng) species are analysed using comprehensive two‐dimensional gas chromatography. Comparison of comprehensive two‐dimensional chromatograms reveals the presence of numerous common components, and possible species‐specific components are also observed. Two‐dimensional bubble plot presentations of GC×GC(FID) data allow ready qualitative and semi‐quantitative comparison of the extracts. The use of GC×GC‐quadrupole MS (GC×GC‐qMS), operated at a scanning rate of 20 Hz, in conjunction with retention data, permits identification of separated (major) components. Whilst this scan speed will be insufficient for reliable quantitative analysis, considerably improved quality of uncorrected spectra, arising from the enhanced separation over single column GC‐MS analysis is apparent. Spectral match qualities of up to 99% are found for a number of components. Comparison of GC×GC‐qMS with GC×GC(FID) indicates that good correspondence of peak position patterns is achieved, which aids component identification. It is shown that (quadrupole) mass spectrometric detection is a useful tool for provision of identification of separated compounds in high‐resolution comprehensive two‐dimensional gas chromatography.
Analysis of plasma catecholamines by liquid chromatography with amperometric detection using a novel SPE ion‐exchange procedure
Authors: Raggi Maria Augusta , Sabbioni Cesare , Nicoletta Gianluca , Mandrioli Roberto , Gerra Gilberto
Published: August 2003

Simultaneous determination of the three main catecholamines (Epinephrine, Norepinephrine, and Dopamine) has been implemented by means of liquid chromatography with amperometric detector working in oxidation at +800 mV. The chromatographic analysis was carried out on a reversed phase column (C8 Rainin 150×4.6 mm ID, 5 μm) with a mixture of methanol and an aqueous solution of 5 mM of citric acid, 20 mg L–1 octanesulfonic acid, and 20 mg L–1 EDTA (pH 2.9) as the mobile phase. An original solid phase extraction pretreatment of plasma samples was developed using cationic ionic exchange cartridges with carboxypropylic adsorbent. The steps of the SPE procedure were carefully checked and optimal elution was carried out with perchloric acid. High extraction yield values were obtained for all catecholamines with good reproducibility. Linearity was observed in the 0.06–3.00 ng mL–1 concentration range for all analytes. LOD and LOQ were respectively 0.03 ng mL–1 and 0.06 ng mL–1. The method was applied successfully to the analysis of some real plasma samples from young volunteers under experimental psychological stress.
Study of electroosmotic flow profile by processing of virtual digital Shah function mask and Fourier transform
Authors: Kitagawa Shinya , Mitsuya Kotaro , Chaiyasut Chaiyavat , Tsuda Takao
Published: August 2003

The electroosmotic flow in a packed capillary column (CEC) and in a rectangular capillary (CE) was observed by using a microscope‐CCD‐camera system. The observed image was captured to PC, and virtual digital Shah function mask processing was applied. The flow velocity was calculated by Fourier transform methods. The flow profile was analyzed by multiple measurements of the flow velocity in adjoining regions. The velocity of the electroosmotic flow in a packed capillary column (ID 150 μm, length 18 mm, packed with cation exchanger) was 4.49 μm/s at any point of the column, and the flow profile was flat. The effect of gravity on electroosmotic flow was also studied. The profile of the electroosmotic flow was almost flat under both 1‐G and microgravity, and the electroosmotic flow velocity under microgravity was found to be significantly faster than that under 1‐G.
Novel column oven concept for cold spot large volume sample enrichment in high throughput temperature gradient capillary liquid chromatography
Authors: Holm Anders , Molander Paal , Lundanes Elsa , Greibrokk Tyge
Published: August 2003

A novel column oven concept with an incorporated cold spot has been tailored for use in capillary liquid chromatography, allowing efficient injection of increased sample volumes by sub‐ambient temperature‐promoted solute enrichment. The column oven system consists of two horizontally connected temperature zones surrounding the packed capillary column. The oven is designed to allow horizontal sliding of the capillary column inside the column oven housing, enabling rapid transportation of the column inlet between the two temperature zones. This design eliminates the time consuming process of re‐cooling the oven after a temperature gradient, which is associated with other column ovens, providing the possibility of high throughput analyses. The cold inlet zone of the oven was operated at sub‐ambient temperatures where elution is suppressed to allow enrichment of large volumes of solutes dissolved in solvents usually associated with high eluting properties. The hot column oven zone allowed temperature‐programmed gradient action, but could also be operated isothermally resulting in a temperature step gradient. The oven was evaluated using the antioxidants Irgafos 168, Irgafos 168‐phosphate, and Irganox 1076 as model compounds using UV‐detection. A 3.5 μm Kromasil C18 0.25 mm ID×20 cm capillary column was used, while the mobile phase and the sample solvent was neat acetonitrile. The flow rate was 5 μL/min. Within‐assay precision and between‐assay precision of peak areas were in the range of 4.3–8.2% relative standard deviation (RSD). The retention time RSD in temperature gradient mode was 2%. The method was linear in the investigated range of 5–100 ng, displaying a correlation coefficient of 0.9995.
Direct high‐performance liquid chromatographic enantioseparation of α‐substituted proline analogues on a quinine‐derived chiral anion‐exchanger stationary phase
Authors: Péter Antal , Vékes Erika , Árki Anita , Tourwé Dirk , Lindner Wolfgang
Published: August 2003

Use of a quinine‐derived chiral anion‐exchanger stationary phase for the direct high‐performance liquid chromatographic enantiomer separation of N‐protected unusual α‐substituted proline analogues is reported. The chromatographic conditions (eluent composition, pH, and buffer concentration) were varied to achieve optimal separation. The readily prepared 2,4‐dinitrophenyl derivatives were well separable, with good efficiency and high resolution. The elution sequences of the enantiomers of the derivatives were determined. Knowledge of the elution sequence allows identification of the configuration of the α‐substituted proline analogues in peptide epimers resulting from use of the racemates in the peptide synthesis. The method also proved suitable for determination of the enantiomeric purity of proline analogues obtained by asymmetric synthesis.
Investigation of the retention behaviour of steroids with calixarene‐based stationary phases by modern NMR spectroscopy
Authors: Skogsberg Urban , Händel Heidi , Gesele Elke , Sokoließ Torsten , Menyes Ulf , Jira Thomas , Roth Ulrich , Albert Klaus
Published: August 2003

A separation of four structurally similar steroids was performed on two calix[8]arene based stationary phases. It was observed that two of the steroids had a reversed retention order when the columns were changed. This implies that two different retention mechanisms are taking place when the analytes are separated. In order to evaluate the mechanism responsible for the reversal of the retention order an extensive study of the interactions between the stationary phases and the analytes was undertaken. By performing a series of transferred NOESY measurements in the suspended state valuable information was obtained about the strengths of the interactions between the analytes and the stationary phases. The magnitudes of the integrals from the trNOESY measurements showed a good correlation with the k´ values obtained from the chromatographic evaluation. The retention mechanism is based mainly on hydrophobic interactions. However, the reversal of the elution order was mainly due to an additional π‐π interaction between one of the analytes and the stationary phase.
Characterization of complex mixtures of polyglycerol fatty acid esters using temperature and solvent gradients in packed capillary LC
Authors: Andersen Thomas , Holm Anders , Skuland Inger Lill , Trones Roger , Greibrokk Tyge
Published: August 2003

A highly complex sample of polyglycerol fatty acid esters has been characterized using both temperature gradient and solvent gradient reversed‐phase packed capillary LC coupled to ELSD and ESI‐TOF‐MS. The techniques showed fairly similar performance in terms of selectivity and efficiency, providing a nice separation of not only the polyglycerol mono‐, di‐, tri‐ and tetra‐fatty acid esters, but also the non‐reacted polyglycerols. The different groups were identified by coupling the packed capillary LC system to a TOF‐MS using an electrospray interface, although the identification of the latest eluting groups in the temperature gradient separation was hampered due to significant column bleeding at elevated column temperatures. By calculating the peak areas in the ELSD chromatograms, the PGE sample was estimated to contain 20.2 ± 0.4 and 22.6 ± 0.5% non‐reacted polyglycerols, 44.4 ± 1.9 and 34.1 ± 1.4% mono‐fatty acid esters, 26.2 ± 1.5 and 27.9 ± 1.7% di‐fatty acid esters, 7.7 ± 0.7 and 12.6 ± 1.0% tri‐fatty acid esters, and 1.4 ± 0.2 and 2.8 ± 0.3% tetra‐fatty acid esters in temperature and solvent gradient mode (n = 3), respectively. The intra‐day precision of the retention times was 0.5–1.4% (n = 3) in the temperature gradient mode, while it was 0.3–1.7% (n = 3) in the solvent gradient mode.