bluuebunny/crossref_metadata_2025 huggingface dataset:
Qualitative and quantitative evaluation of annonaceous acetogenins by high performance liquid chromatography
Authors: Gromek Danuta , Hocquemiller Reynald , Cavé André
Published: March 2007

A high performance liquid chromatographic (HPLC) method for the separation, identification and quantification of Annonaceous acetogenins under isocratic or gradient conditions, using ultraviolet, refractometric or evaporative light scattering (ELSD) detection is reported. The system, consisting of a μBondapak C 18 (10 μm) column and a combination of isocratic, step and linear gradient elutions with water and acetonitrile, allowed all six acetogenins of Annona muricata to be well resolved and separated. Well resolved and symetrical peaks were also obtained for other acetogenins with a variety of substitution patterns under isocratic conditions using methanol: water in the ratio of 90:10 to 80:20 or acetonitrile: water in the ratio of 90:10 to 70:30 as mobile phases. The effect of the number, position and type of substituents are discussed. HPLC using μBondapak C 18 (10 μm) column as stationary phase and acetonitrile: water as a mobile phase was successful for the separation of two epimeric acetogenins: rolliniastatin‐1 and rolliniastatin‐2. In order to demonstrate the possibility of quantifying the acetogenins in crude extracts, the quantitative evaluation of annonacin in the seeds of A. muricata was carried out. Semipreparative separations of some acetogenins by HPLC are also reported.
Liquid chromatography coupled with mass spectrometry in the analysis of alkaloids
Authors: Verpoorte R. , Niessen W. M. A.
Published: March 2007

General aspects of liquid chromatography‐mass spectrometry (LC‐MS) are discussed such as type of interfaces, ionization modes, solvent compatibility and stationary phases, all with special reference to the analysis of alkaloids. The literature on LC‐MS of various classes of alkaloids is reviewed.
A general method for high performance liquid chromatography of pyrrolizidine alkaloid free bases andN‐oxides
Authors: Brown Milford S. , Molyneux Russell J. , Roitman James N.
Published: March 2007

A reverse phase, ion‐pair high performance liquid chromatographic method for the separation of five distinct structural subclasses of pyrrolizidine alkaloids has been developed. The system consists of a μBondapak CN or Nova‐Pak Phenyl column in a radial compression apparatus, eluted isocratically with methanol: water (27:73) containing 0.01 M dibutylammonium phosphate. Symmetrical, well‐resolved peaks were obtained for 30 pyrrolizidine alkaloids within a 15 min elution time. Both the free base and theN‐oxide forms of the alkaloids can be analysed under the same conditions. The elution times are indicative of the relative polarities of the alkaloids being separated.
Determination of cyanogenic glucosides in white clover (Trifolium repens L.) by high performance liquid chromatography
Authors: Stochmal A. , Oleszek W.
Published: March 2007

A high performance liquid chromatographic method used for the determination of cyanogenic glucosides in flax seed has been modified to make it suitable for the analysis of these compounds in dried white clover (Trifolium repens L.) samples. Moreover, the extraction of glycosides from clover samples and purification of exracts on the C18 support prior to analysis has been developed. Linamarin and lotaustralin were identified in T. repens cv. Armena in concentrations of 1.29 and 3.13 mg/g of dry matter, respectively.
Accurate molecular mass determination by mass spectrometrical techniques: Differentiation of soybean lipoxygenase isoenzymes
Authors: Scheller G. , Stahl B. , Weyd S. , Karas M. , Hillenkamp F. , Schreier P.
Published: March 2007

Molecular mass determinations for the four lipoxygenase isoenzymes from soybean seeds were compared using two mass spectrometrical (MS) techniques as well as gel permeation chromatography and sodium dodecylsulphate‐polyacrylamide gel electrophoresis. The data obtained by MS techniques were in good agreement with the molecular masses evaluated from the corresponding cDNA. The MS techniques allowed to distinguish between the lipoxygenase isoenzymes and to check the purity of enzyme preparations.
Rapid high performance liquid chromatographic quantification of valepotriates in hairy root cultures of Valeriana officinalis L. var. sambucifolia Mikan
Authors: Gränicher F. , Christen P. , Vuagnat P.
Published: March 2007

The quantitative determination of valepotriates in Valeriana officinalis L. var. sambucifolia Mikan hairy roots by a new high performance liquid chromatographic (HPLC) method is reported. The quantification is based on the simultaneous isocratic determination of the monoene and diene derivatives at one wavelength (208 nm). The analysis is rapid and highly reproducible, giving results similar to those obtained with a currently used HPLC method in which valepotriate quantification is undertaken using two separate runs.
Structural elucidation of infuscatin, a diterpenoid from Salvia infuscata
Authors: Ortega Alfredo , Maldonado Emma , Jankowski Christopher K. , Van Calsteren Marie Rose , Díz† Eduardo
Published: March 2007

A new trihydroxy neoö‐clerodane diterpene, infuscatin, has been isolated from Salvia infuscata. Its structure was established as 15,16‐epoxy‐4β, 8α, 10β‐trihydroxy neo‐cleroda‐1,13(16),14‐trien‐17,12R,18,19‐diolide by spectroscopic means, including 1H1H COSY, 13C NMR, DEPT 135, DEPT 90, COLOC and NOE differential experiments.
Determination ofS‐adenosyl‐L‐methionine andS‐adenosyl‐L‐homocysteine in plants
Authors: Edwards Robert
Published: March 2007

A sensitive method has been developed for the simultaneous determination of S‐adenosyl‐L‐homocysteine (SAH) and S‐adenosyl‐L‐methionine (SAM) in a variety of plant tissues. Samples were extracted in acid and the extracts cleaned up and concentrated by a combination of partitioning with diethyl ether and cation exchange chromatography using phosphocellulose paper. After elution from the phosphocellulose paper with a minimal volume of 6M HCI, SAM and SAH were quantified by ion‐pair reversed phase high performance liquid chromatography with UV detection at 257 nm. Recoveries were monitored using a spike of [14C]‐SAM and were typically between 30 and 40%. In alfalfa, peas and maize the levels of SAM exceeded those of SAH, and in peas levels of SAM were higher in young roots and shoots than in older tissues. When alfalfa cell cultures were treated with a fungal elicitor preparation, the levels of SAM and SAH increased approximately two‐fold over a 12 h period and then declined.
Health literacy and patient understanding of screening tests for aneuploidy and neural tube defects
Authors: Cho Regina N. , Plunkett Beth A. , Wolf Michael S. , Simon Charla E. , Grobman William A.
Published: March 2007

Objective

To determine if health literacy is associated with patient understanding of prenatal screening tests for fetal aneuploidy and neural tube defects.

Methods

We performed a prospective observational study on a cohort of English‐speaking patients receiving prenatal care in two resident‐staffed ambulatory clinics. Health literacy was measured using the Rapid Estimate of Adult Literacy in Medicine‐7. Understanding of the prenatal screening tests was assessed using a modified Maternal Serum Screening Knowledge Questionnaire.

Results

Over an 8‐month period, 125 patients were approached, and 101 (81%) consented to the study. Thirty‐eight (38%) women demonstrated low health literacy. Patients with low health literacy were more likely to demonstrate inadequate understanding when compared to those with adequate health literacy (97% versus 11%, respectively; P < 0.01). Similarly, patients with < 12th grade education were more likely to have inadequate understanding when compared to patients with > 12th grade education (53% versus 30%, respectively; P = 0.02). Health literacy is a more sensitive and specific predictor of inadequate understanding than education (sensitivity 84% versus 70%, respectively, P < 0.05; specificity 98% versus 47%, respectively, P < 0.05).

Conclusion

Patients with low health literacy are more likely to demonstrate inadequate understanding of these prenatal screening tests than women with adequate health literacy. Copyright © 2007 John Wiley & Sons, Ltd.
The correlation between coping strategies, doctor–patient/spouse relationships and psychological distress among women cancer patients and their spouses
Authors: Gilbar Ora , Zusman Alla
Published: March 2007

Objectives: The objectives of the study were (1) to assess similarities and differences between women cancer patients and their spouses in terms of coping strategies, psychological distress and doctor–patient/spouse relationships; and (2) to investigate the impact of formal social support, namely the doctor–patient relationship and coping strategies, on patients' and spouses' psychological distress.

Method: Fifty‐seven women with cancer, and their spouses, completed questionnaires that measured distress (BSI), coping strategies (PF, EF) and doctor–patient relationships (Pat, Md).

Results: Patient distress was greater than that of spouses. Patients used more strategies involving problem‐focused coping than spouses. A positive relationship was found between patients and spouses in terms of psychological distress, paternalism and emotion‐focused strategies. Emotion‐focused strategies were found to impact patient psychological distress, as indicated in a hierarchical regression model.

Conclusion: The paternalism relationship model is an important factor in patient psychological distress but not in spousal psychological distress. Copyright © 2007 John Wiley & Sons, Ltd.
Exploring the economic impact of breast cancers during the 18 months following diagnosis
Authors: Gordon Louisa , Scuffham Paul , Hayes Sandi , Newman Beth
Published: March 2007

The economic impact on individuals with breast cancer is not well understood. We sought to identify and describe the direct and indirect economic losses to breast cancer survivors in Australia. A longitudinal, population‐based study of 287 women was used to explore economic outcomes (costs and lost income) for women with breast cancer 0–18 months post‐diagnosis. Survey methods collected data on out‐of‐pocket costs, care‐giving support, paid and unpaid work reductions, and perceptions from participants on these financial impacts. Bootstrapping was used to estimate 95% confidence intervals around means. Data were sub‐grouped by cost type, age category and disease severity. Lost income, health service expenditures and lost unpaid work were the greatest sources of economic burden. Women with positive lymph nodes reported significantly higher costs than those with negative lymph nodes (US$6674 versus US$3533, p<0.001), and younger women (⩽50 years) with positive lymph nodes experienced costs 80% greater than older women (US$8880 versus US$4937, p<0.001). Economic costs related to breast cancer may continue to affect women 18 months post‐diagnosis. Economic research adds an important dimension for understanding the impact of breast cancer, and findings may be used to help improve supportive care services for women and families confronted by this disease. Copyright © 2007 John Wiley & Sons, Ltd.
Assessment is not enough: a randomized controlled trial of the effects of HRQL assessment on quality of life and satisfaction in oncology clinical practice
Authors: Rosenbloom Sarah K. , Victorson David E. , Hahn Elizabeth A. , Peterman Amy H. , Cella David
Published: March 2007

The potential benefits of health‐related quality of life (HRQL) assessment in oncology clinical practice include better detection of problems, enhanced disease and treatment monitoring and improved care. However, few empirical studies have investigated the effects of incorporating such assessments into routine clinical care. Recent randomized studies have reported improved detection of and communication about patients' concerns, but few have found effects on patient HRQL or satisfaction. This study examined whether offering interpretive assistance of HRQL results would improve these patient outcomes. Two hundred and thirteen participants with metastatic breast, lung or colorectal cancer were randomly assigned to one of three conditions: usual care; HRQL assessment or HRQL assessment followed by a structured interview and discussion. Interviews about patients' assessment responses were conducted by a research nurse, who then presented HRQL information to the treating nurse. HRQL and treatment satisfaction outcomes were assessed at 3 and 6 months. No significant differences were found between study conditions in HRQL or satisfaction. Results suggest that routine HRQL assessment, even with description of results, is insufficient to improve patient HRQL and satisfaction. It is suggested that positive effects may require supplementing assessment results with specific suggestions for clinical management changes. Copyright © 2007 John Wiley & Sons, Ltd.
The lower limit of mountain permafrost in the Russian Altai Mountains
Authors: Fukui Kotaro , Fujii Yoshiyuki , Mikhailov Nikolai , Ostanin Oleg , Iwahana Go
Published: March 2007

Permafrost‐indicator features, such as rock glaciers, pingos and ice‐wedge polygons, exist at many locations in and around the South Chuyskiy Range of the Russian Altai Mountains (∼50°N). The distribution of these features suggests that the altitudinal range of the sporadic/patchy permafrost zones and the widespread discontinuous/continuous permafrost zones are 1800–2000 m ASL and above 2000 m ASL, respectively. The lower limit of discontinuous permafrost is approximately 200 m lower than in the Mongolian Altai, which are at a similar latitude. Cold air drainage and/or temperature inversions during winter within U‐shaped valleys together with a thin snow cover because of low precipitation during the same season likely cause the lower permafrost limit in the study area. The calibrated 14C ages of tree remnants found in a rock glacier front in the lower Akkol valley were 293 ± 21 years BP and 548 ± 21 years BP. Given the time of emergence from beneath the Sofiyskiy glacier, this rock glacier developed between 3800–2600 and 550 years BP. Copyright © 2007 John Wiley & Sons, Ltd.
Analysis of the HLA class I associated peptide repertoire in a hepatocellular carcinoma cell line reveals tumor‐specific peptides as putative targets for immunotherapy
Authors: Alvarez Iñaki , Carrascal Montserrat , Canals Francesc , Muixí Laia , Abián Joaquín , Jaraquemada Dolores
Published: March 2007

HLA class I molecules present peptides on the cell surface to CD8+ T cells. The repertoire of peptides that associate to class I molecules represents the cellular proteome. Therefore, cells expressing different proteomes could generate different class I‐associated peptide repertoires. A large number of peptides have been sequenced from HLA class I alleles, mostly from lymphoid cells. On the other hand, T cell immunotherapy is a goal in the fight against cancer, but the identification of T cell epitopes is a laborious task. Proteomic techniques allow the definition of putative T cell epitopes by the identification of HLA natural ligands in tumor cells. In this study, we have compared the HLA class I‐associated peptide repertoire from the hepatocellular carcinoma (HCC) cell line SK‐Hep‐1 with that previously described from lymphoid cells. The analysis of the peptide pool confirmed that, as expected, the peptides from SK‐Hep‐1 derive from proteins localized in the same compartments as in lymphoid cells. Within this pool, we have identified 12 HLA class I peptides derived from HCC‐related proteins. This confirms that tumor cell lines could be a good source of tumor associated antigens to be used, together with MS, to define putative epitopes for cytotoxic T cells from cancer patients.
Proteomic and transcriptomic analysis of human CD8+ T lymphocytes over‐expressing telomerase
Authors: Thadikkaran Lynne , Menzel Olivier , Tissot Jean‐Daniel , Rufer Nathalie
Published: March 2007

Human T lymphocytes have a finite life span resulting from progressive telomere shortening that occurs at each cell division, eventually leading to chromosomal instability. It has been shown that ectopic expression of the human telomerase reverse transcriptase (hTERT) gene into various human cells results in the extension of their replicative life span, without inducing changes associated with transformation. However, it is still unclear whether cells that over‐express telomerase are physiologically and biochemically indistinguishable from normal cells. To address this question, we compared the proteome of young and aged human CD8+ T lymphocytes with that of T cells transduced with hTERT. Interestingly, we found no global changes in the protein pattern in young T cells, irrespective of telomerase expression. In contrast, several relevant proteins with differential expression patterns were observed in hTERT‐transduced T cells with extended life span upon long‐term culture. Altogether, our data revealed that T lymphocytes over‐expressing telomerase displayed an intermediate protein pattern, sharing a similar protein expression not only with young T cells, but also with aged T cells. Finally, the results obtained from this global proteomic approach are in agreement with the overall gene transcription profiling performed on the same T‐cell derived clones.
Non‐radiative relaxation of excited states of non‐bridging oxygen hole centers in silica
Authors: Zatsepin A. F. , Kortov V. S. , Biryukov D. Yu.
Published: March 2007

Processes involved in the excited‐state relaxation of non‐bridging oxygen hole centers (NBOHCs) were studied in glassy SiO2 using luminescence, optical absorption and photoelectron emission spectroscopy. It was shown that photoexcited NBOHCs generally have three channels of relaxation. Along with radiative transitions responsible for the luminescence band at 1.9 eV, two non‐radiative channels caused by transitions between levels of photoexcited state were observed. The first non‐radiative channel was connected with transformation of the electron excitation energy to thermal lattice vibrations and represented an intracenter process of NBOHC luminescence quenching (the activation barrier was 0.05 eV). The second non‐radiative relaxation channel for excited NBOHCs was identified as thermally activated external luminescence quenching with the energy barrier of 0.46 eV. As a result of realization of the specified process, the transfer of the excitation energy from NBOHCs to oxygen‐deficient centers (ODCs) acting as electron emitters took place. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
EXAFS and XRD studies of nanocrystalline cerium oxide: the effect of preparation method on the microstructure
Authors: Savin S. L. P. , Chadwick A. V. , Smith M. E. , O'Dell L. A.
Published: March 2007

There is considerable interest in nanocrystalline materials due to their unusual properties, such as enhanced ionic conductivity in the case of nanocrystalline ionic solids. This has potential commercial applications, particularly for oxide ion conductors. However, a detailed knowledge of the microstructure is important in fully understanding the novel properties exhibited by nanocrystalline materials. The final microstructure of a material is dependent on the preparation method used, for example, sol‐gel and ball‐milling methods are commonly used in the preparation of nanocrystalline oxides. Additionally, there is a problem in maintaining the materials in nanocrystalline form when they are subjected to elevated temperatures. We have been exploring strategies to restrict the growth of nanocrystalline oxides and have found that adding a small amount of an inert material, e.g. SiO2 or Al2O3, is particularly effective. We will report XRD and EXAFS studies of nanocrystalline ceria prepared by sol‐gel, sol‐gel pinned and ball‐milling methods and the effect of preparation method on the final microstructure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation into thallium sites and defects in doped scintillation crystals
Authors: Blacklocks A. N. , Chadwick A. V. , Jackson R. A. , Hutton K. B.
Published: March 2007

Thallium doped caesium iodide, CsI(Tl), and sodium iodide, NaI(Tl) are two of the most efficient scintillators developed and are already widely used for radiation detection and imaging applications. Their use in fast imaging applications however has been hindered by a long lasting high level of afterglow – the percentage of the luminescence pulse remaining a short time after excitation. Very little is known about the point defects in these crystals, such as structure and concentrations, and the first step to understanding the causes of the afterglow is to understand the nature of the defects responsible for the scintillation. In this paper the local structure of the thallium activator ion has been investigated via EXAFS spectroscopy and some basic intrinsic defects calculated using the General Utility Lattice Program (GULP). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Origin of 1/f noise as a runaway phenomenon due to the zeropoint field (ZPF) of quantum electrodynamics (QED)
Authors: Cavalleri Giancarlo , Bosi Leonardo
Published: March 2007

The origin of electron transport noise whose power spectral density is inversely proportional to the frequency f has been realized after 80 years of attempts. Here we give its conceptual explanation that has required a sequence of five ideas and corresponding results: 1) The reduction of the nonlinear Boltzmann equation with electron‐electron (e –e) interaction to a Fokker‐Planck (denoted as e –e FP) equation containing two electron collision frequencies ν1 and ν2; 2) the application of the e –e FP to materials and its‐steady state solution that depends on ν1(υ), ν2(υ), and the square a2 of the acceleration a = e E/m; 3) the steadystate solution of the e –e FP equation becomes similar to the Fermi‐Dirac distribution function if a2 is considered as mainly due to the zero‐point field (ZPF) of quantum electrodynamics (QED) or, realistically, of stochastic electrodynamics (SED); 4) in this δυ range the e –e FP is similar to the usual FP solved by Stenflo when ν (υ) ∝ 1/υ. It is just because of aZPF that for any conduction current there is always a small interval δυ for the electron speed υ where ν1 ∝ ν2 ∝ 1/υ, condition that is at the threshold of runaways. The relevant time‐dependent Green solution of the e –e FP equation decreases as τ–ε with ε < 0.006. The consequent power spectral density S (f) turns out to be ∝ 1/f1–ε in an indefinite medium. Our S (f) also depends on the electrons concentration N and excellently fits the experimental data; 5) In a finite sample the memory or a fluctuation is preserved beyond the electron transit time because the transmission of information is mainly due to e –e interactions and to the diffusion coefficient that diverges at the threshold of runaways. A pimple (due to fluctuation) in the distribution function on the electron speeds is almost crystallized, decaying as τ–0.005 without any cut‐off at the transit time. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computer modelling of the optical properties of rare‐earth doped metal fluorides
Authors: Jackson R. A. , Valerio M. E. G. , Amaral J. B. , Couto dos Santos M. A. , Maddock E. M.
Published: March 2007

A computational approach to calculating the optical properties of doped metal fluoride materials is presented, and applied to rare earth doping in the BaY2F8 and LaF3 systems. Optimal locations for dopant ions are predicted, along with solution energies and charge compensation mechanisms. Energy levels for dopant ions are predicted using adapted crystal field calculations. The results of the predictions are compared with experimental data. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radiation effects in sapphire optical fibers
Authors: Sporea Dan , Sporea Adelina
Published: March 2007

Radiation effects on sapphire optical fibers were investigated using off‐line gamma‐ray, neutron and electron beam irradiation and on‐line proton irradiation. The optical attenuation of these optical fibers was studied from UV to IR (200 nm – 1700 nm). For the in‐situ measurements radioluminescence was also investigated as function of the total irradiation dose. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Holographic properties of azobenzene oligomers with differently bonded chromophore groups
Authors: Ozols A. , Saharov Dm. , Kampars V. , Kokars V. , Kreicberga J. , Ratyeva S.
Published: March 2007

Holographic properties of two types (I and II, specified in the text) of azobenzene oligomers (ABO) have been experimentally studied in the spectral region of low absorption at 633 nm. In the case of type I ABO the chromophore groups were covalently bonded to either tolyl‐polyurethane or hexamethylene‐polyurethane matrix. In the case of type II ABO azobenzene chromophores were dispersed in polystyrene matrix, and their concentration was varied from 0.005 to 0.200 mol/l. Samples were in the form of 10 µm thick films. In both cases the diffraction efficiency exposure time dependences were measured for the holographic grating period of 2 (m at 633 nm. The diffraction efficiency of more than 2% and the specific recording energy down to 30 ‐ 60 J/(cm2%) were achieved in both cases. In the case of type I ABO the best results were achieved with 4‐nitronaphtylazobenzene chromophore groups in hexamethylene‐polyurethane matrix. The chromophore concentration threshold within 0.01 – 0.04 mol/l range, the holographic efficiency growth with chromophore concentration and the photosensitization effect were found in the case of type II ABO. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fractal characteristics of metal clusters self‐assembled in alkali halide matrices
Authors: Enculescu M. , Enculescu I.
Published: March 2007

Metal nanoclusters of Ag and Au were obtained in alkali halide crystals (NaCl, KBr and KCl). The fractal character of the structures is proved by the fractal dimensions calculated using a home made computer program. The self aggregation of the metallic structures is governed in both cases (Ag and Au) by the DLA mechanism. This is proved by the values of the fractal dimension calculated using two methods, sandbox and box‐counting, which are between 1.7 and 1.8 for Ag and for Au between 1.7 and 1.9. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman studies of ferroelectric domain walls in lithium tantalate and niobate
Authors: Capek Pavel , Stone Greg , Dierolf Volkmar , Althouse Chad , Gopolan Venkat
Published: March 2007

Using confocal Raman spectroscopy at low temperature we investigated the perturbation of the phonon modes across a domain wall region as a function of sample stoichiometry in lithium tantalate and niobate. For all samples, we found that the Raman spectra were changed. The intensity of the A(LO) phonon modes and most of the E(TO) phonon modes were shifted and changed in their relative intensity over a 20 μm length scale. Our measurements suggest that the intensity of the A(LO) phonon modes change due to local charges induced by pyroelectric effect and/or photoionization, while the observed shifts are due to strains that are not relaxed in the domain wall region. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Relative features of the principal and secondary luminescence lifetimes in quartz
Authors: Chithambo M.L. , Ogundare F.O.
Published: March 2007

The form of time‐resolved luminescence spectra has been studied for quartz annealed at 800 °C and pulse‐stimulated at 470 nm. Depending on the measurement temperature and the irradiation dose, the spectra may be de‐convolved into two possible components to produce a principal and subsidiary lifetime component. Measurements between 20 and 200 °C show that both components are affected by thermal quenching of the associated luminescence, qualitatively so for the subsidiary one, but with an activation energy of 0.71 eV for the principal lifetime. Regarding influence of irradiation, time‐resolved spectra consist of a single component below about 260 Gy but two components thereafter independent of irradiation. The irradiation‐dependent features of the lifetimes are accounted for in terms of the relative importance of the various luminescence centers in quartz. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anomalous zero‐phonon line broadening of the (NV)– center in diamond
Authors: Nishikori H. , Mita Y. , Nisida Y. , Okada M. , Nakashima T.
Published: March 2007

Absorption measurements were carried out on the (NV)– centers in diamond at low temperature after laser illumination. It was observed that the width of the zero‐phonon line becomes persistently more than two times larger. This characteristic phenomenon was studied in detail about excitation photon energy, illumination time, sample temperature and recovery nature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron paramagnetic resonance line shape investigation of the 29Si hyperfine doublet of the E′γ center in a‐SiO2
Authors: Buscarino Gianpiero , Agnello Simonpietro , Parlato Aldo
Published: March 2007

We report an experimental study by electron paramagnetic resonance (EPR) spectroscopy of the E′γ center and of its hyperfine structure, consisting in a pair of lines split by 42 mT. Our results show that two types of E′γ centers can be distinguished on the basis of the EPR line shapes of their main resonance line and hyperfine structure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dielectric spectra of doped and X‐ray irradiated calcium fluoride crystals
Authors: Nicoara I. , Munteanu M. , Pecingina‐Garjoaba N. , Stef M. , Preda E. , Lucaci A.
Published: March 2007

Calcium fluoride crystals doped with PbF2 and codoped with LiF, NaF have been grown using the vertical Bridgman method. The frequency (1‐100 kHz) dependence of the real and imaginary parts of the complex dielectric constant, ε1 and ε2, have been studied in the temperature range 160‐300 K; the activation parameters of the relaxation process have been determined for various doped and X‐irradiated calcium fluoride crystals. The optical absorption spectra of the crystals are also investigated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Extended defects in organic molecular semiconductors: the role of crystal growth mechanisms
Authors: Moret M. , Campione M. , Raimondo L. , Sassella A. , Tavazzi S. , Aquilano D.
Published: March 2007

Atomic force and optical microscopy analysis of topographic features on the {001} faces of the organic semiconductor quaterthiophene is employed to establish connections between bulk and surface structure. Observation of interlaced step patterns on growth spirals is indicative of the presence of layers rotated by 180° about the normal of the (001) crystal face. This result, together with the height of the exposed step ledges of the order of 10‐100 nm, suggests the complex polytypic nature of these crystals due to periodic polysynthetic twinning. Therefore, the basic monoclinic structure of quaterthiophene is modified giving rise to many different periodicities along [001] even in one crystallite. The consequences on physical properties of these phenomena arising from growth mechanisms are briefly discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman and infrared spectroscopic characterization of LiNbO3 crystals grown from alkali metal oxide solvents
Authors: Dravecz G. , Kovács L. , Péter Á. , Polgár K. , Bourson P.
Published: March 2007

LiNbO3 crystals grown from Na2O, Rb2O, and Cs2O containing fluxes were characterized by infrared and Raman spectroscopic methods. Pure, nearly stoichiometric crystals with 49.7–50.0 mol% Li2O content were obtained from solvents containing Rb2O and Cs2O, while Na2O entered the crystal as a dopant. The intensity ratio of two OH– absorption peaks at 3480 and 3465 cm–1 in thermal equilibrium was shown to be a useful and accurate parameter for the determination of the lithium content of pure LiNbO3 crystals close to the stoichiometric composition. From the remarkable change of both infrared and Raman spectra in crystals grown from Na2O solvent, the incorporation of Na on Li sites was assumed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tin nanoclusters obtained in potassium chloride by thermal annealing
Authors: Apostol E. , Enculescu M. , Polosan S. , Vasile E. , Topa V.
Published: March 2007

Tin nanoclusters were obtained in potassium chloride crystals following the electrolytic coloration of KCl:Sn2+ and KCl: Sn2++Ca2+ crystals and thermal annealing at various temperatures and times. Electrolytic coloration of KCl:Sn2+ crystals produces electronic centers inside of samples, presumably negative metal ions of tin. Optical absorption measurements were performed on as grown sample, colored and thermal annealed samples. The behavior of the samples with Sn colloids was compared with theoretical predictions according to Mie's theory. Tin nanoclusters in KCl exhibit an absorption band with a peak at 215 nm. The structure of the nanoclusters was studied by optical absorption and transmission electron microscopy means. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic methods for the determination of the composition of potassium lithium niobate crystals
Authors: Hajdara I. , Lengyel K. , Dravecz G. , Kovács L. , Péter Á. , Szaller Zs.
Published: March 2007

Beside the ferroelectric Curie‐temperature, the ultraviolet and infrared spectra of potassium lithium niobate (K3Li2Nb5O15, KLN) were shown to be very sensitive to the compositional variations observed in the crystals along the growth axis. The absorption edge shifts to the UV with decreasing Nb content, independently of the K/Li ratio of the crystal, while the ratio of the intensities of the OH– stretching vibrational bands at 3440 and 3520 cm–1 depends on the K/Li ratio, as well. Combining these optical spectroscopic methods with Curie‐temperature measurements one can determine the crystal composition with high accuracy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermoluminescence of LiF and F2 color centers
Authors: Baldacchini G. , Davidson A. T. , Kalinov V. S. , Kozakiewicz A. G. , Montereali R. M. , Nichelatti E. , Voitovich A. P.
Published: March 2007

Light emitted when heating crystalline materials previously exposed to ionizing radiation is commonly known as thermoluminescence. The resultant glow curve is related to the material, the impurities and the defect centers generated by the irradiation. Several efforts have been made in the past to associate glow peaks with specific defect centers. Recently, in the case of LiF we established a link between F3+ and F3 centers and the temperature region of the glow curve below 200 °C. This result was obtained by using especially treated samples with known concentration of color centers in first place, and annealing measurements in second place. By continuing these studies, it has been possible to establish a further link between F2 centers and a prominent feature of the glow curve near 260 °C. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical absorption, paramagnetic resonance and depolarisation currents in MgAl2O4 spinel
Authors: Paiva Roberto , Carvalhaes Magalhães , Blak Ana Regina
Published: March 2007

Optical Absorption (OA), Electron Paramagnetic Resonance (EPR) and Thermally Stimulated Depolarisation Currents (TSDC) techniques were applied to study the effects of irradiation and thermal treatments in the formation, aggregation and destruction processes of dipole defects in MgAl2O4 spinel. Irradiated MgAl2O4 crystals present two OA bands centred at 3.4 eV and 5.1 eV. The 3.4 eV band increases with the irradiation‐dose, stabilizes its maximum height for doses near 10 kGy and is completely destroyed for thermal treatments above 500 K. This same band decays when the sample is maintained at room temperature reaching a constant value after a few weeks. The EPR spectrum is composed by two superimposed bands at g = 2.011. The gamma dose dependence, the thermal treatments between 370 K and 500 K and the thermal decay of the two bands at room temperature, show that each band behaves in a different way thus indicating that they are associated with two different defects. Gamma dose of 10 kGy produces a TSDC band at 245 K. When the sample is maintained at room temperature, after the gamma irradiation, for several weeks, a displacement in the peak position to 290 K, is observed. Thermal treatments above 500 K destroy the 290 K band. This band is associated to at least two V‐type centres. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Decay time of polaron photoluminescence in congruent lithium niobate
Authors: Harhira A. , Guilbert L. , Bourson P. , Rinnert H.
Published: March 2007

The intensity, the peak wavelength and the decay time of polaron photoluminescence in congruent lithium niobate are measured versus temperature from 77 K to 290 K. The radiative relaxation shows quasi athermal behaviour (τR ≈ 9 µs) whereas the nonradiative relaxation follows arrhenius law with activation energy of 220 meV. The crossing point between radiative and nonradiative lifetimes is about 210 K. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of the condensed phase on a surface of fiber crystals during their growth by micro pulling down method
Authors: Cherepanova E. V. , Tcherepanov A. N. , Shulgin B. V.
Published: March 2007

New experimental data of the structure of a surface of fiber crystals (NaF, LiF and BGO) are presented in this paper. The explanation of observable features of a structure of their surface is offered. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
UV light energy storage and thermoluminescence in AlN ceramics
Authors: Trinkler L. , Berzina B. , Auzina A. , Benabdesselam M. , Iacconi P.
Published: March 2007

AlN ceramics, untreated and subjected to oxygen ion implantation, are studied for potential application in TL dosimetry of UV light. Based on photoluminescence and thermoluminescence measurements there are shown advantages of the selection of the 480 emission band for TL signal recording instead of the previously used 400 nm band: higher intensity of the TL signal, lower fading rate of the accumulated TL signal, excitation region (270‐340 nm) corresponding to UV‐B range, monitoring of which is actual in UV dosimetry. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coloured inorganic‐organic films on glass
Authors: Cholewa‐Kowalska K. , Wojtach K. , Olejniczak Z. , Laczka M.
Published: March 2007

Two kinds of inorganic‐organic hybrid materials (A and B class) were obtained in the form of thin films on glass. As starting materials were used: PhTES + TEOS (A class); PhTES + GPTMS + TBA (B class). Hybrid materials were coloured using ORASOL type dyes. The coloured coatings were put on glass by dip‐coating technique. The structure of hybrid matrix was examined by spectroscopic methods: FTIR, 29Si MAS NMR, 27Al MAS NMR. On this base structural units of hybrid were identified. UV/VIS spectra of thin films were measured directly after obtainment as well as after thermal and chemical treatment of samples. It has been found that UV/VIS spectra originate from electron transitions between ligands and transition metal ions. The coloured centres in hybrid matrix show good thermal and chemical resistance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence of nanoporous C12A7 compound
Authors: Feldbach E. , Kirm M. , Liblik P. , Maaroos A. , Avarmaa T. , Mändar H.
Published: March 2007

A comparison of excitation spectra of photostimulated and ordinary luminescence enabled us for the first time to determine experimentally the framework energy gap value Eg= 6.5 eV of 12CaO · 7 Al2O3(C12A7). The most short‐wavelength luminescence band (peaked at ∼4.5 eV) detected at 10 K can be interpreted either as luminescence of intrinsic excitations or as recombination of electrons, captured in sub‐nanometer sized cages of C12A7 crystal structure, with holes of valence band. The main peak of thermostimulated luminescence (134–137 K) is composed of two emission bands peaked at 2.8 and 4.5 eV. The calculated activation energy 0.44 eV of spectrally resolved (at 4.5 eV) thermally stimulated luminescence peak at 137 K is close to the value (0.4 eV) needed to initiate the inter‐cage charge transfer of electrons (polaron hopping) between cages. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermal transformation of colour centres in LiF crystals with given content of oxygen, hydroxyl and metal ions
Authors: Baldacchini G. , Goncharova O. , Kalinov V. S. , Montereali R. M. , Vincenti A. , Voitovich A. P.
Published: March 2007

Processes of radiation creation and annealing of Frenkel defects, as well as their transformation processes, have been studied in γ ‐irradiated LiF single crystals containing various impurities, by means of measurements of thermally stimulated changes in absorption and emission spectra. Important information about the density of colour centres in LiF, which depends on γ ‐irradiation doses, impurities and temperatures, has been obtained for small crystal contents of oxygen, hydroxyl and metal ions. A comparison of annealing parameters of the LiF crystals subjected to different doses of irradiation, but to the same thermal bleaching procedures, has been performed and the results are critically discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic transitions in Li2B4O7:Cu single crystals
Authors: Nagirnyi V. , Kotlov A. , Corradi G. , Watterich A. , Kirm M.
Published: March 2007

A low‐temperature study of Li2B4O7:Cu crystals by methods of time‐resolved polarization spectroscopy using synchrotron radiation in the 4–20 eV region and microsecond Xe flash lamp pulses in the 3–6 eV region is reported. The results strongly support the conclusion about a low‐symmetry position of the Cu+ ion in its ground state. The temperature dependence of the decay kinetics of the Cu+‐related 3.35 eV emission indicates a triplet nature for the relaxed excited state of the Cu+ centres. A pseudo off‐centre position of the Cu+ ion in the relaxed excited state is suggested. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hydroxil ions in scheelite type molybdates and tungstates
Authors: Kovács L. , Péter Á. , Ivleva L. I. , Baraldi A. , Capelletti R.
Published: March 2007

The presence of hydroxil ions has been detected for the first time in as‐grown scheelite type crystals. A number of stretching vibrational bands were observed in PbMoO4 and BaWO4 crystals at 8 K, while only very weak OH– absorption was found in CaMoO4, SrMoO4 and SrWO4 in the 3200–3600 cm–1 wavenumber range. The anharmonicity of the stretching modes for all bands in PbMoO4 and BaWO4 was found to be in agreement with that observed in other oxides. The model of weak coupling to a single phonon band was used to interpret the temperature dependence of the OH– band positions and halfwidths. Strong polarization dependence was observed for the OH– vibrations in both crystals indicating that the O–H dipoles incorporate the lattice along different O–O bonds. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nanocrystalline SrTiO3:Eu3+ and BaTiO3:Eu3+: fluorescence spectroscopy and optical studies of structural phase transitions
Authors: Feofilov S. P. , Kaplyanskii A. A. , Kulinkin A. B. , Zakharchenya R. I.
Published: March 2007

The results of optical studies of Eu3+ ions doped nanocrystalline materials which undergo structural phase transitions: SrTiO3:Eu3+ and BaTiO3:Eu3+ are presented. Nanocrystalline SrTiO3 and BaTiO3 samples with crystallite sizes about 25–50 nm were produced by the sol‐gel process. The Eu3+ 5D0,1 → 7Fn fluorescence spectra were studied. Time‐resolved fluorescence spectra enabled to separate different kinds of Eu3+ centers in BaTiO3 samples. Fluorescence spectroscopy of probe Eu3+ ions was used to detect the structural Oh – D4h phase transition in nanocrystalline SrTiO3. The Eu3+ excited states lifetimes were studied in a wide temperature range and the effects of modified refractive index of the media on radiative transitions were observed. The study of ferroelectric C4v – Oh phase transition in nanocrystalline BaTiO3 with optical second harmonic generation technique revealed remarkable hysteresis in the temperature dependence of the second harmonic intensity. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
O– bound polarons in oxide materials
Authors: Schirmer O. F.
Published: March 2007

The optical absorption of holes, self‐trapped at one of the equivalent O2– sites next to acceptor defects in crystalline oxide materials, is treated. The holes are localized by lattice distortion, forming small polarons with typical stabilization energies EP of 1 eV. The light‐induced hole transfer from an initial O– site to an equivalent O2– neighbour occurs under Franck‐Condon conditions, leading to the widest possible homogeneous absorption bands, having high oscillator strength, typically 0.1, and peak energies between 8/3 EP and 1 EP, for 4 up to 12 equivalent neighbours. The basic absorption features, including characteristic excited state tunnelling splittings, are exemplified with representative defects of high point symmetry. Such polarons arise in numerous materials after excitation by light or ionizing radiation. They play important roles as sources of coloration in non‐linear optic and photorefractive compounds, gemstones, as acceptor defects in oxide semiconductors and as catalytic agents, if at a surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radiation‐induced defects in chalcogenide glasses characterized by combined optical spectroscopy, XPS and PALS methods
Authors: Shpotyuk O. , Kovalskiy A. , Golovchak R. , Zurawska A. , Jain H.
Published: March 2007

Temperature‐dependent optical absorption spectroscopy, high‐resolution X‐ray photoelectron spectroscopy and positron annihilation lifetimes spectroscopy are utilized to understand radiation‐induced changes in Ge–Sb–S chalcogenide glasses. Theoretically predicted topological scheme of γ‐induced coordination defect formation in stoichiometric Ge23.5Sb11.8S64.7 glass composition is supported by these measurements. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetism due to defects/oxygen vacancies in HfO2 thin films
Authors: Hong Nguyen Hoa
Published: March 2007

Room temperature ferromagnetism with a large magnetic moment was observed in un‐doped HfO2 films grown on Yttrium Stabilized Zirconia substrates. It is known that neither Hf4+ nor O2– is magnetic. On the other hand, HfO2 bulk is clearly diamagnetic. Since it is certain that there is no contamination in any substrate, it is not possible to attribute such a large magnetic moment to impurities. Certainly thin film form, which might create necessary defects and/or oxygen vacancies, must be the main reason for this un‐doped insulating oxide to become ferromagnetic. Filling up oxygen vacancies can reduce the magnetic moment enormously, and at some critical point, can destroy the ferromagnetic ordering completely. This confirms the assumption that magnetism in HfO2 thin films originates from defects and/or oxygen vacancies. Defects seem to be mostly located at the interface between the film and the substrate. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence of ZrO2 and HfO2 thin films implanted with Eu and Er ions
Authors: Lange S. , Kiisk V. , Aarik J. , Kirm M. , Sildos I.
Published: March 2007

A spectroscopic study of Eu‐ and Er‐implanted ZrO2 and HfO2 thin films was performed. Photoluminescence (PL) of trivalent ions under band‐to band excitation of the host was observed. Annealing up to 1100 °C was required to maximize the PL signal intensity. The Eu3+ ion was used as a probe of local structure. The PL excitation spectra were recorded both for intrinsic and impurity‐related emission. Different channels of indirect excitation of the RE ions were revealed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)