bluuebunny/crossref_metadata_2025 huggingface dataset:
N-terminal pro-atrial natriuretic peptide as a biochemical marker of long-term interventional success after radiofrequency catheter ablation of paroxysmal supraventricular tachyarrhythmias
Authors: Brueckmann Martina , Bertsch Thomas , Hoffmann Ursula , Lang Siegfried , Kaden Jens J. , Wolpert Christian , Huhle Guenter , Borggrefe Martin , Haase Karl K.
Published: August 2004

Radiofrequency (RF) catheter ablation has been shown to be highly effective in the treatment of supraventricular tachycardias. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (B-type natriuretic peptide; BNP) are secreted by the heart mainly in response to myocardial stretch induced by volume load. The aim of the present study was to determine the time course of the N-terminal prohormone forms of ANP (NT-proANP) and BNP (NT-proBNP) in patients undergoing radiofrequency (RF) catheter ablation for paroxysmal supraventricular tachycardias.

Serial blood samples were taken from 13 patients with symptomatic paroxysmal supraventricular tachycardias undergoing RF ablation and from 13 age- and gender-matched healthy controls. Blood was taken before ablation (day 0, baseline), and at day one and day 120 after ablation. Levels of NT-proANP were significantly higher before RF ablation (4862 ± 726 pmol/l) as compared to day one (2021 ± 220 pmol/l) and day 120 after RF ablation (2470 ± 349 pmol/l) (with p < 0.01 on day one and p < 0.05 on day 120; n = 13). The size of the left atrium decreased from 41.0 ± 5.5 mm before ablation to 34.9 ± 5.9 mm (n = 13; p < 0.05) on day 120 as measured by M-mode echocardiography. Levels of NT-proBNP showed comparable values before and on day one and day 120 after ablation and were not significantly elevated as compared to healthy controls.

NT-proANP levels are increased in patients presenting with paroxysmal supraventricular tachycardias and decrease one day after radiofrequency catheter ablation, possibly reflecting a transient reduction of ANP secretion from injured myocardial cells. Lower NT-proANP levels in the long-term time course may result from reduction of atrial volume load and reconstitution of atrial architecture after successful treatment of supraventricular tachycardias. NT-proANP may serve as a useful laboratory marker to describe the long-term interventional success after RF ablation.
Preventing in vitro lipoperoxidation in the malondialdehyde-thiobarbituric assay
Authors: Gonzalo Ricardo , Vives-Bauza Cristofol , Andreu Antonio L. , García-Arumí Elena
Published: August 2004

The malondialdehyde-thiobarbituric acid assay is widely used to study lipid peroxidation. Among the various methods used to perform the assay, the most widely accepted is the quantification of malondialdehyde using the thiobarbituric acid reaction, followed by reversed-phase chromatography. However, unacceptable results may be obtained as malondialdehyde can be produced in vitro. To study the conditions that inhibit in vitro lipid peroxidation, malondialdehyde levels were measured in cultured cells using different concentrations of butylated hydroxytoluene, EDTA or a combination of both. Butylated hydroxytoluene alone inhibits in vitro lipid peroxidation effectively. EDTA reduces artificially produced malondialdehyde, but not totally. Finally, the combination of EDTA and butylated hydroxytoluene does not improve the results obtained using butylated hydroxytoluene alone. The conclusion is that in the malondialdehyde-thiobarbituric acid assay it is necessary to add an inhibitor of the in vitro lipid peroxidation and assay the necessary concentration depending on the specimen used.
Oxidative stress: potential of distinct peroxide determination systems
Authors: Lindschinger Meinrad , Nadlinger Karl , Adelwöhrer Norbert , Holweg Karin , Wögerbauer Markus , Birkmayer Jörg , Smolle Karl-Heinz , Wonisch Willibald
Published: August 2004

When reactive oxygen species attack biological structures, peroxides, which are short-lived oxidative intermediates, are generated. We evaluated the potential of two different, commercially available peroxide activity assays (Pox-Act and d-ROMS) to see whether the results were associated with the clinical condition of subjects who were participating in a routine health care program. Furthermore, we determined the total antioxidant status (TAS) and the titer of autoantibodies against oxidized low-density lipoprotein (oLAb) to verify the hydroperoxide measurements.

Subjects with medical conditions (hereafter referred to as patients) had significantly increased serum peroxide levels compared to healthy subjects. The d-ROMS kit indicated that 86% of subjects had an increased level of total peroxides. Although the assays had a significant correlation (p < 0.001), 34% of the subjects had an increased total peroxide concentration in the Pox-Act assay that was clearly associated with clinical symptoms. Furthermore, the sensitivity of the Pox-Act assay was 35 times higher than that of the d-ROMS kit. In subjects with medical conditions, there was a trend toward a decreased TAS and a slightly increased oLAb titer in comparison to healthy subjects, but this was not statistically significant. The Pox-Act assay seems to be a valuable tool for the determination of total peroxides, while the results from the d-ROMS kit should be considered with caution.
Quality assessment in cytogenetic and molecular genetic testing: the experience of the Italian Project on Standardisation and Quality Assurance
Authors: Taruscio Domenica , Falbo Vincenzo , Floridia Giovanna , Salvatore Marco , Pescucci Chiara , Cantafora Alfredo , Marongiu Cesarina , Baroncini Anna , Calzolari Elisa , Cao Antonio , Castaldo Giuseppe , Bricarelli Franca Dagna , Guanti Ginevra , Nitsch Lucio , Pignatti Pier Franco , Rosatelli Cristina , Salvatore Francesco , Zuffardi Orsetta
Published: August 2004

The first Italian national trial of external quality assessment in genetic testing was organised within the framework of the “Italian National Project for Standardisation and Quality Assurance of Genetic Tests”. Sixty-eight Public Health Service laboratories volunteered for the trial, which involved molecular genetic tests (cystic fibrosis, β-thalassaemia, familial adenomatous polyposis coli and fragile-X syndrome) and cytogenetic tests (prenatal and postnatal, the latter included cancer cytogenetics). The response rate was high (88.2%). The level of analytical accuracy was good, i.e., the percentage of laboratories that correctly genotyped all samples was 89.3% for cystic fibrosis, 90.9% for β-thalassaemia, 100% for familial adenomatous polyposis coli (despite two laboratories did not complete the analysis because the amount of DNA was considered insufficient), and 90.5% for fragile-X syndrome. Written reports differed widely and were judged “inadequate” in over 50% of cases. Most laboratories from the present study already have experience in previous European external quality assessments for at least one genetic test; this can explain the higher analytical accuracy in the Italian external quality assessment with respect to quality control programmes in other countries. Collaborative networks are strongly suggested to improve the quality of the reports.
Guidelines for blood smear preparation and staining procedure for setting up an external quality assessment scheme for blood smear interpretation. Part I: control material
Authors: Corrons Juan-Lluis Vives , Albarède Stephanie , Flandrin George , Heller Silke , Horvath Katalin , Houwen Berend , Nordin Gunnar , Sarkani Erika , Skitek Milan , Blerk Marjan Van , Libeer Jean-Claude
Published: August 2004

Blood smear analysis is a well known technique in medical laboratories. Clinical relevance of this analysis and its interpretation are very important. Consequently, monitoring of laboratory performance by an external quality assessment scheme is strongly recommended. Most starting external quality organizers set up a scheme for clinical chemistry. Due to a lack of guidance documents, many organizers are reluctant to offer a hematology scheme. This article aims to be a very practical guidance document for external quality assessment organizers for the set up of blood smear schemes.
Measurement of serum and plasma osmolality in healthy young humans – influence of time and storage conditions
Authors: Seifarth Christian C. , Miertschischk Johannes , Hahn Eckhardt G. , Hensen Johannes
Published: August 2004

Background: The precise measurement of osmolality is crucial in the differential diagnosis of disorders of water balance. Storage conditions, and freezing and thawing of serum or plasma samples before osmometry may influence the accuracy of measured values. Methods: A series of serum and plasma samples of 25 healthy young individuals were stored under different conditions at different temperatures (room temperature (22°C), 7°C, –21°C, –78°C) for up to 56 days. Before freezing a protein-stabilizing agent (bacitracin) was added to one part of the samples. Osmolality was examined using the freezing point method. Results: At room temperature osmolality was stable for up to 3 days but showed a tendency toward an increase that was significant on day 14. In contrast, at 7°C an initial significant decrease in serum osmolality occurred (day 1), which was followed by a slow increase. Serum samples stored at –21°C showed a significantly lower osmolality on the 14th day compared to baseline. Adding bacitracin before freezing reduced this decrease by more than half, but the deviation was still significant. In samples stored at –78°C no significant alteration of osmolality from baseline was observed over the observation period of 56 days if samples were thawed in a 37°C water bath. Conclusion: Immediate measurement of osmolality is most reliable in order to obtain accurate values, although storing at room temperature does not influence osmolality significantly during the first 3 days. If storage is necessary for longer, samples should be stored at –78°C and must be thawed quickly (at 37°C). Under these conditions reliable values can be obtained from frozen serum or plasma. Storage at 7°C is not recommended. If samples are stored at –21°C the addition of a protein-stabilizing agent may be useful.
High in-hospital mortality of intensive care patients with nucleated red blood cells in blood
Authors: Stachon Axel , Holland-Letz Tim , Krieg Michael
Published: August 2004

The detection of nucleated red blood cells (NRBCs) in blood of patients suffering from a variety of severe diseases is known to be highly associated with increased mortality. Blood analyzers to routinely measure NRBC concentrations are now available. However, the diagnostic and prognostic significance of this parameter for intensive care patients has not been evaluated. Using a Sysmex XE-2100 analyzer, NRBC concentrations were determined in blood samples from 421 patients treated in intensive care units (general and accident surgery, cardiothoracic surgery, and internal medicine) of a university hospital. NRBCs were found at least once in 19.2% of all patients. The mortality of NRBC-positive patients (n = 81) was 42.0% (n = 34); this was significantly higher (p < 0.001) than the mortality of NRBC-negative patients (5.9%, n = 340). The NRBC concentration was 115 ± 4 × 10
Frequency of –163 C > A and 63 C > G single nucleotide polymorphism of cytochrome P450 1A2 in two African populations
Authors: Dandara Collet , Basvi Patience T. , Bapiro Tashinga E. , Sayi Jane , Hasler Julia A.
Published: August 2004

Cytochrome P450 1A2 (CYP1A2) is an important member of the cytochrome P450 superfamily of enzymes because of its involvement in the metabolism of some carcinogens and therapeutically important drugs. As a result, factors affecting the activity of the enzyme are the focus of considerable research effort as they may have important pharmacological or toxicological implications. CYP1A2 has been shown to exhibit a genetic polymorphism with most of the data, however, coming from studies in Caucasian and Oriental populations. In this study therefore, we investigated the frequencies of two point mutations, –163C > A and 63C > G, in two Bantu African populations. A total of 214 healthy subjects were recruited from Zimbabwe (n = 143) and Tanzania (n = 71). The two single nucleotide polymorphisms were detected using polymerase chain reaction-restriction fragment length polymorphism analysis. The frequency of –163A was 57% (95% confidence interval (CI), 54%, 60%) and 49% (95% CI, 45%, 53%) among Zimbabweans and Tanzanians, respectively, but the difference between the two populations was not statistically significant (p = 0.123). The base change 63C > G was not found in any of the subjects from the two populations. We report here a high frequency of –163C > A base change and an absence of the 63C > G change in the two African populations.
Long-term stability of endogenous B-type natriuretic peptide (BNP) and amino terminal proBNP (NT-proBNP) in frozen plasma samples
Authors: Mueller Thomas , Gegenhuber Alfons , Dieplinger Benjamin , Poelz Werner , Haltmayer Meinhard
Published: August 2004

The aim of the present study was to assess the long-term stability of endogenous B-type natriuretic peptide (BNP) and amino terminal proBNP (NT-proBNP) in plasma samples stored at –20°C without addition of protease inhibitors (e.g., aprotinin). Stability of BNP and NT-proBNP was tested in 60 EDTA plasma samples with BNP values between 30 and 420 pg/ml. Initial BNP and NT-proBNP plasma concentrations were determined within four hours after blood collection using the AxSYM BNP and the Elecsys NT-proBNP assays. Subsequently, all samples were stored at –20°C and were thawed for the second BNP and NT-proBNP determination on the two instruments after one day, 30 days, 60 days, 90 days and 120 days, respectively. Mean recovery (i.e., residual immunoreactivity) of BNP and NT-proBNP expressed in percent of the initial value for the given time interval of storage was calculated. Mean recovery of BNP was less than 70% after one day of storage at –20°C and decreased to less than 50% after two to four months of storage (e.g., recovery of endogenous BNP after three months of storage at –20°C ranging from 0% to 71%). In contrast, mean recovery of NT-proBNP was generally greater than 90%, irrespective of the duration of storage at –20°C (e.g., recovery of endogenous NT-proBNP after three months of storage at –20°C ranging from 91% to 112%). In conclusion, the determination of endogenous BNP with the AxSYM assay using frozen plasma samples may not be valid under the conditions tested. In contrast, NT-proBNP as measured by the Elecsys assay may be stored at –20°C for at least four months without a relevant loss of the immunoreactive analyte.
Antioxidant capacity of the human pericardial fluid: does gender have a role?
Authors: Seres Leila , Soós Pál , Székely Mária , Horkay Ferenc , Selmeci László
Published: August 2004

The aim of the present study was to assess the antioxidant capacity in the serum and pericardial fluid of patients undergoing heart surgery for coronary heart disease (CHD) or valvular heart disease (VHD) and to find out whether there are gender-related differences in the antioxidant defense. This study involved 85 patients (35 VHD and 50 CHD) undergoing elective heart surgery. Blood samples from the peripheral vein and from the pericardial fluid were taken intraoperatively. Variables determined in the serum and pericardial fluid were: total protein, albumin, uric acid and antioxidant capacity. In the total patient population the antioxidant capacity in the pericardial fluid was lower than in the serum but still relatively high as determined by two independent techniques. No major differences were seen in serum or pericardial fluid antioxidant capacity between the two patient groups. In the overall patient population uric acid (p < 0.05), albumin (p < 0.01) and total protein concentrations (p < 0.01) were, however, significantly greater in the pericardial fluid of male than of female patients. The pericardial fluid may contribute to the local antioxidant defense of the myocardium. It appears that male gender confers advantage in this respect. It remains to be elucidated whether this finding has any implication for the higher risk for women of perioperative complications and of cardiovascular mortality after coronary bypass grafting or coronary angioplasty.
Comparison of serum digoxin concentration monitoring by fluorescence polarization immunoassay on the TDxFLx® and dry chemistry enzyme immunoassay on the Vitros 950
Authors: Solnica Bogdan
Published: August 2004

The aim of the study was to compare the results of digoxin assays performed using fluorescence polarization immunoassay (FPIA) on the TDxFLx
Multicenter analytical performance evaluation of the Elecsys® proBNP assay
Authors: Sokoll Lori J. , Baum Hannsjörg , Collinson Paul O. , Gurr Eberhard , Haass Markus , Luthe Hilmar , Morton James J. , Nowatzke William , Zingler Christiana
Published: August 2004

The purpose of this multicenter study was to evaluate the technical performance of the automated Elecsys proBNP (brain natriuretic peptide) assay, which is indicated as an aid in the diagnosis of individuals suspected of having congestive heart failure. The Elecsys proBNP assay is an electrochemiluminescent immunoassay employing two polyclonal NT-proBNP-specific antibodies in a sandwich test format. The study was performed on the three Elecsys analyzers (E 1010, E 2010, and E 170) at eight different sites world-wide. Within- and total precision were ≤3%, with total precision slightly higher on the Elecsys E 170 instrument with multiple modules. Reproducibility among sites and platforms was <5%. Precision at particularly low NT-proBNP concentrations was assessed down to approximately 25 pg/ml with CVs of 12.6% at 29.2 pg/ml and 9.6% at 38.5 pg/ml for the Elecsys 1010/2010 and E 170, respectively. Linearity was evaluated up to 25,000 pg/ml with a sample-based non-linear response observed with recoveries of <90% for proBNP concentrations <10 000 pg/ml. Slopes ranged between 0.92 and 1.02 and intercepts from –5.3 to 10.4 pg/ml (r≥0.998) among the three types of analyzers. Slopes were 4.95 and 4.53 in comparison to the Biosite Triage and Shionogi BNP assays. There was no assay interference, and no effect of barrier gels, tube composition, or freeze-thaw. NT-proBNP concentrations in EDTA plasma were up to 10% lower than in serum or heparinized plasma and the analyte was stable at 4°C for up to 72 hours (the maximum time tested). There was no circadian rhythm in normal subjects or congestive heart failure patients and there was no effect of drawing position. In summary, the Elecsys proBNP assay exhibits good technical performance and is suitable for use in routine clinical laboratories to aid in the diagnosis of congestive heart failure.
The effects of initial spacing on wood density, fibre and pulp properties in jack pine (Pinus banksiana Lamb.)
Authors: Kang Kyu-Young , Zhang Shu Y. , Mansfield Shawn D.
Published: August 2004

Relationships between basic tree and wood properties, and species, seed source, geographic location, site conditions and management decisions are very complex. The objective of this study was to quantify the effects of forest management practices on wood density, fibre and pulp properties in jack pine, one of the most important commercial species in Northern America. A better understanding of the relationship between initial spacing and wood and end-product quality should help define improved forest management strategies required to produce quality wood and products in the future. On the basis of the oldest jack pine initial spacing trial established in 1941 by the USDA Forest Service, this study examined the impact of four different initial spacing trials on tree growth, wood density, fibre and pulp properties of jack pine.

The results clearly show that initial stand spacing has a significant effect on all of these properties, and thus it is possible to improve yield and wood and pulp fibre properties of jack pine through stand density regulation. Additionally, a positive effect of pre-commercial thinning on fibre properties was also demonstrated. As a consequence of these results, basic prescription information for decision-making in the establishment of jack pine plantations with desirable pulp properties can be elucidated.
An improved procedure for isolation of residual lignins from hardwood kraft pulps
Authors: Capanema Ewellyn Augsten , Balakshin Mikhail Yurievich , Chen Chen-Loung
Published: August 2004

Residual lignin preparations were isolated from birch, aspen and Eucalyptus grandis kraft pulp by enzymatic hydrolysis of the pulps with cellulase:hemicellulase mixture. Residual lignin preparations were characterized by investigation of nitrogen content, carbohydrate composition and molecular mass distribution. The use of enzyme with high activity and optimization of enzyme charge resulted in significant decrease in protein contaminants in residual lignin preparations as compared to previously published results. A second order law correlation between enzyme mass charge and nitrogen content in birch residual lignin preparations indicates a strong effect of enzyme charge on the amount of protein contaminants. However, the enzyme charge in the range studied does not appreciably affect either the yields of the residual lignin preparations or percentage and composition of carbohydrates in these preparations. The optimal enzyme charge was highest for Eucalyptus grandis pulp and lowest for birch pulp. It has been suggested that a significant part of the hardwood residual lignin in pulps, especially in E. grandis pulp, consists of low molecular mass lignin fragments bonded to pulp carbohydrates. Higher amount of glucose in E. grandis residual lignin preparation compared to those from birch and aspen implied a higher frequency of lignin-cellulose bonds in eucalypt pulp. Different fractions of birch residual lignin have rather similar molecular mass distribution, which was not affected by the charge of the enzyme. Eucalypt residual lignin preparation had higher molecular mass than birch residual lignin.
Application of confocal Raman spectroscopy for the topochemical distribution of lignin and cellulose in plant cell walls of beech wood (Fagus sylvatica L.) compared to UV microspectrophotometry
Authors: Röder Thomas , Koch Gerald , Sixta Herbert
Published: August 2004

In a comparative study, the topochemical distribution of lignin in individual cell wall layers of beech wood tissue was determined by confocal Raman spectroscopy and scanning UV microspectrophotometry. The Raman technique was additionally applied to the determination of cellulose content in individual wall layers. In good agreement, the two methods showed maxima of lignin distribution in middle lamellae and cell corners, along with a minimum of cellulose content.
UV-microscopic analysis of acetylated spruce and birch cell walls
Authors: Hansmann Christian , Schwanninger Manfred , Stefke Barbara , Hinterstoisser Barbara , Gindl Wolfgang
Published: August 2004

Spruce and birch earlywood was acetylated to different weight percent gains using three different acetylation procedures. The absorbance spectra of secondary cell wall and compound cell corner middle lamella were determined by means of UV microscopy. Analysis of the spectra showed that the characteristic lignin absorbance peak in the UV spectrum of wood around 280 nm shifted to shorter wavelengths in acetylated samples. A distinct relationship between achieved weight percent gains after acetylation and observed spectral shifts could be established revealing a certain potential to measure acetylation on a cellular level by means of UV microscopy.
On-line study of lignin behaviour in dilute alkaline solution by the SEC-UV method
Authors: Bikova Tatjana , Treimanis Arnis , Rossinska Galina , Telysheva Galina
Published: August 2004

The dynamic method for monitoring ionisation of the lignin functional groups in a 0.1 N NaOH solution at ambient temperature by means of the SEC technique with multiwave UV detection was performed. An increase in absorbance at 210, 278, 304, 320 and 350 nm was examined to reveal the ionisation dynamics in respect to functional groups’ acidity; that is, carboxyl groups, carbonyl- and double-bond conjugated phenol hydroxyls. A distinctive response of absorbance at 210 and 278 nm on the ionisation of carbonyl- and double-bond-conjugated phenols was found. Simultaneous characterisation of lignin by molecular weight (MW) and chemical heterogeneity was performed. A non-uniform distribution of reactive sites over the MW distribution for commercial kraft lignin (Curan) was found employing the family of chemical composition distribution curves. The redistribution of extended chromophore structures over time along the lignin’s MW distribution causes a misrepresentation of the UV chromatogram pattern and influences the accuracy of MW values.
Nondestructive characterization of wood by monitoring of local elastic anisotropy and dynamic nonlinearity
Authors: Solodov Igor , Pfleiderer Klaus , Busse Gerhard
Published: August 2004

The results of non-contact measurements of local in-plane elastic anisotropy in wood by monitoring the flexural plate wave velocity as a function of azimuth angle of propagation are reported. The Focused Slanted Transmission of air-coupled ultrasound is used to generate and detect locally the flexural waves in wood as well as to measure their velocities. The analysis presented shows that for thin plates the flexural wave velocity can be readily used to evaluate the anisotropy of Young’s modulus. This conclusion is confirmed by measurements of the plate wave anisotropy factors for veneer laminae and cross-ply laminates of spruce and beech. The technique is sensitive enough to detect the anisotropy variation of earlywood caused by the incorporation of latewood areas in growth rings. A new approach based on dynamic nonlinearity of wood is developed and applied to acoustic imaging of wood structure and detecting of defects in wood. The hysteresis mechanism of the dynamic nonlinearity is shown to dominate in clear wood and to manifest in a primary generation of odd acoustic harmonics. Local maxima of the odd higher harmonic amplitudes in the LR- and LT-planes of softwood are observed in the earlywood area close to latewood/earlywood transition interface that indicates the lower stiffness and strength of wood in those areas. The higher-order even harmonics and subharmonics in the nonlinear vibration spectra of wood are mostly produced by “clapping” in defect areas. Measurements of local amplitudes of these modes are applied to nonlinear acoustic imaging of cracks, delaminations and knots in wood and wood composites.
Chemical reaction of maritime pine sapwood (Pinus pinaster Soland) with alkoxysilane molecules: A study of chemical pathways
Authors: Sèbe Gilles , Tingaut Philippe , Safou-Tchiama Rodrigue , Pétraud Michel , Grelier Stéphane , De Jéso Bernard
Published: August 2004

The chemical modification of maritime pine sapwood (Pinus pinaster) with alkoxysilanes was studied according to three different pathways: carbamoylation with 3-isocyanatopropyltriethoxysilane, etherification with 3-glycidoxypropyltrimethoxysilane and alcoholysis of n-propyltrimethoxysilane. Grafting was confirmed by weight percent gain calculations (WPG), infrared spectroscopy (FTIR) as well as 13C and 29Si NMR CP MAS analysis. Signals of the grafted groups in the different spectra were assigned and the reactivity of the trialkoxysilane moieties towards wood was discussed. Experiments with model wood blocks showed that the reactions investigated occurred within the wood cell walls. Grafted chemicals were found to be relatively stable with regard to water leaching but only slight dimensional stabilisation was noted after treatment.
Thermal forming of chemically modified wood to make high-performance plastic-like wood composites
Authors: Timar Maria Cristina , Maher Kevin , Irle Mark , Mihai Maria Daniela
Published: August 2004

Chemically modified wood composites were obtained via the compression moulding of thermoplasticised Aspen (Populus tremula) sawdust. This sawdust was previously prepared by esterification with maleic anhydride (MA) and subsequent oligoesterification with maleic anhydride and glycidyl methacrylate (GMA). The thermoplastic properties of the chemically modified wood resulting from different modification procedures were confirmed and compared by compression-moulding experiments leading to preliminary and final products. An SEM study of the resulting products clearly showed that the oligoesterified wood had partially melted under pressure and temperature, such that the overlapping and surface melting of particles ensured adhesive bonding between those particles. A new type of wood/thermoplastic-wood composite was obtained. In these composites, the melted part of the modified wood plays the role of the cohesive matrix whilst none-melted wood remains as a fibrous reinforcing material. FTIR spectra suggested that changes in the chemical structure of the modified wood are possible during the thermal forming process (e.g. polymerisation of C=C double bonds).

The final composites were yellowish-brown, glossy, plastic-like products that showed interesting physical, mechanical and biological properties. They are water-resistant and dimensionally stable and display good electrical insulating behaviour. Their mechanical properties (bending strength of ca. 64 MPa and tensile strength of ca. 36 MPa) are in the typical range for plastics and conventional wood-fibre/plastic composites, and are superior to common wood products such as fibreboards and particleboards. Furthermore, the outstandingly high internal bond (ca. 3.0 MPa) highlights the totally different adhesion mechanism operating in these new types of composites. Although the novel composites are much more resistant to decay than the original unmodified wood, they remain ultimately biodegradable plastic-like composites.
Eco-composite from poly(lactic acid) and bamboo fiber
Authors: Lee Seung-Hwan , Ohkita Tsutomu , Kitagawa Kazuo
Published: August 2004

Bamboo fiber-filled poly(lactic acid) (PLA) eco-composites were prepared by mechano-chemical compositing with bamboo fiber (BF)-esterified maleic anhydride (MA) (BF-e-MA) in the presence of dicumyl peroxide as a radical initiator. Tensile properties of the composites were improved by adding BF-e-MA and the dicumyl peroxide. A sufficient effect of the addition on the tensile property of the composites was observed even in the presence of the dicumyl peroxide of 0.25%. However, the composites with BF-e-MA usually showed a higher activation energy for thermal flow, indicating that their flow became more difficult, because molecular motions were rather suppressed by cross-linking of BF-e-MA with the PLA matrix resin. The crystallization temperature of PLA became higher by the addition of BF and BF-e-MA in non-isothermal crystallization. It was confirmed by scanning electron microscope and polarizing microscope observation that interfacial properties between BF and PLA were improved after the addition of BF-e-MA. A diffusion coefficient (D) of water in the PLA/BF composites with BF-e-MA was smaller than that in the composites without BF-e-MA. An equilibrium water-sorption amount (M∞) was higher in the order of composites without BF-e-MA>composites with BF-e-MA>pure PLA.
Bamboo fiber (BF)-filled poly(butylenes succinate) bio-composite – Effect of BF-e-MA on the properties and crystallization kinetics
Authors: Lee Seung-Hwan , Ohkita Tsutomu
Published: August 2004

Effects of bamboo fiber (BF)-esterified with maleic anhydride (MA) (BF-e-MA) on the properties of BF-filled poly(butylene succinate) (PBS) bio-composites were investigated. Adding 5% BF-e-MA increased the tensile strength of the PBS/BF (70/30) composite from 21 MPa to 28 MPa in the presence of radical initiator (0.5%). Melt viscosity was also increased by adding BF-e-MA. The Avrami and Ozawa equations were used to analyze the isothermal and nonisothermal crystallization kinetics, respectively. At the same crystallization temperature, all composites showed lower values for the Avrami and Ozawa exponents than pure PBS. Furthermore, the values for the PBS/BF-e-MA composite were smaller than those for the PBS/BF composite. Equilibrium water-sorption amount (M
∞) were highest for the composite without BF-e-MA, followed by the composites with BF-e-MA and finally pure PBS. The diffusion coefficient (D) was smaller for the composites with BF-e-MA than without. Scanning electron microscopy revealed that interfacial adhesion between BF and PBS matrix was improved after addition of BF-e-MA.
Dimensional changes in Corsican pine (Pinus nigra Arnold) modified with acetic anhydride measured using a helium pycnometer
Authors: Hill Callum A.S. , Ormondroyd Graham A.
Published: August 2004

Helium pycnometry was used to determine the changes in volume of wood samples of Corsican pine following modification with acetic anhydride. Results were compared with changes in volume determined from external dimensions only. Percentage change in volume, as determined from external dimensions of the sample, showed a non-linear relationship with weight percentage gain as a result of acetylation; whereas percentage volume change determined by helium pycnometry showed a linear relationship. The difference in volume as determined by the two methods is explained by considering volume change of the lumens as level of cell wall substitution increases. Results obtained in this study show that volume increases due to chemical modification, when determined by measurement of external dimensions, should not be used to evaluate changes in cell wall volume.
Microwave-enhanced release of formaldehyde from plywood
Authors: Saito Yukie , Nakano Kousuke , Shida Satoshi , Soma Tomoaki , Arima Takanori
Published: August 2004

The release of formaldehyde from plywood has been greatly reduced by treatment with microwave radiation. Formaldehyde emission in the air was measured before, during, and after 2.45-GHz microwave treatment. The concentration of formaldehyde released increased with microwave irradiation and, after the microwave treatment, decreased to a level below that of nontreated material. Microwaves were effective in releasing free formaldehyde from the plywood, which is preferable to it being emitted as “potential formaldehyde” via hydrolysis. Microwaves released formaldehyde from plywood samples more effectively compared to samples subjected to thermal energy from external heating. This suggests that microwaves directly activate free formaldehyde molecules, which have a polarity that is susceptible to microwaves. Microwave treatment is expected to be an effective way to reduce free formaldehyde emissions from wood-based materials containing resins.
Artificial weathering of tropical woods. Part 2: Color change
Authors: Kishino Masanori , Nakano Takato
Published: August 2004

This paper describes the change in diffuse reflectance Fourier transform infrared (DRIFT) and ultraviolet-visible (UV-Vis) diffuse reflectance spectra of the following eight tropical woods during artificial weathering up to 600 h in relation to their color changes, especially to yellowing: Amnurana acreana, Acacia auriculiformis, Dipterocarpus spp., Eucalyptus marginata, Eucalyptus robusta, Shorea spp. and Tabebuia spp. with relatively high and low specific gravity. For A. acreana, A. auriculiformis, Dipterocarpus spp. and both Tabebuia spp., Δb* (yellowing) increased with exposure up to 50 h, and decreased above 50 h. For E. marginata, E. robusta and Shorea spp., on the other hand, both Δa* (shift to red) and Δb* decreased with increased exposure time. For woods in which Δb* increased, the Δb* showed a positive dependence on the difference in relative intensity ratio of a band at 1740 cm–1 to that at 2900 cm–1 (ΔD1740/D2900) in DRIFT spectra of specimens before and after exposure. This result indicated that the increased band at 1740 cm–1 played a significant role in the increased Δb*. Then again, also for woods in which Δb* decreased, the ΔD1740/D2900 increased, but was not related to the Db*. The ΔD1740/D2900 for woods in which Δb* decreased had a positive relationship to the difference in remission function at 410 nm (ΔF(R∞)410) in UV-Vis diffuse reflectance spectra for specimens before and after exposure, while woods in which Δb* increased were independent of the ΔF(R∞)410. Therefore, it is suggested that woods in which Δb* increased and decreased differ from one another in the contribution to the increase in the band at 1740 cm–1, resulting in either an increase or decrease of Δb*.
Modellgestützte Moderation in CSCL-Umgebungen – ein Mittelweg zwischen Fremd- und Selbststeuerung (Model Based Support for Self-Directed Learning in CSCL-Environments – an Appropriate Approach between Instruction and Self-Direction)
Authors: Carell Angela , Herrmann Thomas , Kienle Andrea , Schneider Helge
Published: August 2004

Sowohl Ziel als auch Voraussetzung erfolgreicher kollaborativer Lernprozesse ist es, dass Lerngruppen ihren Lern- und Kooperationsprozess weitgehend selbst steuern. In der Praxis setzt sich dieses selbstgesteuerte Lernen aus fremd- und selbstgesteuerten Teilen zusammen. Die bisherigen Ansätze zur Unterstützung kollaborativer Lernprozesse (z.B. cooperation scripts) sind jedoch i.d.R. zu direktiv und deshalb ungeeignet, wenn es um die Förderung selbstgesteuerter Lernprozesse geht. In diesem Beitrag gehen wir der Frage nach, wie eine geeignete Unterstützung solcher Prozesse aussehen kann. Dazu stellen wir das Konzept der modellbasierten Moderation beim CSCL (mod-CSCL) vor, das auf Basis grafischer Modelle Orientierungen anbietet, um Lerngruppen dabei zu unterstützen, ihren gemeinsamen Lernprozess selbstgesteuert zu planen und durchzuführen, ohne sie dabei zu sehr zu reglementieren. Ein besonderes Merkmal unseres Ansatzes ist, dass Lerngrup-pen mit jeweils unterschiedlichem Bedarf an Anleitung unterstützt werden können.
CURE – Eine Umgebung für selbstorganisiertes Gruppenlernen (CURE – an Environment for Self-Organized Collaborative Learning)
Authors: Haake Jörg M. , Schümmer Till , Bourimi Mohamed , Landgraf Britta , Haake Anja
Published: August 2004

CURE unterstützt selbstorganisiertes kooperatives Lernen in verteilten Gruppen über das Internet. Verteilte Teams können sich mit CURE finden und in CURE ihr gemeinsames Lernen selbst organisieren sowie in gemeinsamen Arbeitsbereichen Lernmaterial kooperativ bearbeiten und synchron bzw. asynchron miteinander kommunizieren. Erste Erfahrungen aus dem Pilotbetrieb an der FernUniversität in Hagen zeigen, dass die Benutzer von CURE die Konzepte zur flexiblen Gestaltung des Gruppenlernens erfolgreich anwenden.
Einfluss von Motivation und Didaktischem Design in E-Learning-Umgebungen (Effects of Motivation and Instructional Design on E-Learning Environments)
Authors: Zumbach Jörg , Starkloff Philipp , Schmitt Stefanie
Published: August 2004

Mit einem erhofften wirtschaftlichen Aufschwung setzt die Weiterbildungsbranche auf eine steigende Nachfrage nach modernen Lernformen. Speziell beim E-Learning hat sich in den letzten Jahren trotz Branchenkrise in technologischer Hinsicht einiges getan. Die Akzeptanz von E-Learning ist jedoch nach wie vor fragwürdig: Online-Lernangebote bleiben oft hinter den Erwartungen zurück, die Abbrecherquoten sind hoch und die Lern- und Transferleistungen sind meist nicht besser als bei konventionellen Trainings. Um einer Ablehnung von rein onlinebasierten Lernlösungen entgegen zu wirken, erwarten viele Weiterbildner mit dem Trend zum Blended Learning – einer Integration von E-Learning mit Präsenztraining – die Lerner besser zu erreichen. Trotzdem mangelt es häufig an Lernmotivation der potenziellen Nutzer. Ohne eine grundlegende Bereitschaft zum Lernen wird kein Lernerfolg erzielt, speziell bei selbstgesteuerten Lernangeboten. Wie kann man dennoch die Lernenden motivieren, E-Learning zu betreiben? Technische Verbesserungen allein greifen hier zu kurz. Der folgende Beitrag will aufzeigen, wie motivationale Lernfaktoren wirken und wie sie in Lernkonzeptionen berücksichtigt werden können.
Fit für den Beruf – E-Learning in der Qualifizierung zum Industriemeister Metall (Fit for the Job – E-Learning in Vocational Training for Industrial Teamleaders)
Authors: Rickert Anne , Gidion Gerd
Published: August 2004

Im Projekt „Meisternetz“ sind 12 Online-Lernmodule entstanden, die eine handlungsorientierte Didaktik umsetzen. Komplexe, betriebliche Situationsaufgaben, die aus dem realen Berufsalltag abgeleitet sind, wurden medial umgesetzt mit dem Ziel, angehenden Industriemeistern neben dem Erwerb beruflicher Handlungskompetenz den Einstieg in den Umgang mit neuen Technologien zu erleichtern.
Gebrauchstaugliche Gestaltung von E-Learning-Systemen (Designing Usable E-Learning-Systems)
Authors: Finck Matthias , Janneck Michael , Oberquelle Horst
Published: August 2004

Auf der Basis eines humanistischen Menschenbildes und einer darauf basierenden Didaktik lassen sich zentrale software-ergonomische Erkenntnisse über die gebrauchstaugliche Gestaltung von Büroanwendungen, wie sie z.B. in der ISO 9241, Teil 10, formuliert werden, auf Fragen der Gestaltung gebrauchstauglicher E-Learning-Systeme übertragen. Durch diesen Transfer gelingt sogar eine Konkretisierung auf drei wesentliche Prinzipien für die Gestaltung von E-Learning-Systemen: Medienperspektive, Offenheit und Einfachheit.
GUI Redesign für den RolePlay-Chat, ein Werkzeug für das computervermittelte Rollenspiel (Redesign of a Usable User Interface for Computer Supported Roleplay)
Authors: Jödick Friederike
Published: August 2004

Der vorliegende Beitrag zeigt Defizite der grafischen Benutzungsoberfläche eines kooperativen, Chat-basierten Lernwerkzeugs auf, die hauptsächlich fehlender Awareness zuzuschreiben sind. Als Lösungsansatz wird die Prozess-Awareness präsentiert, die das prozessgesteuerte, selbst organisierte Lernen unterstützt und für den Lernenden handhabbarer macht.
Vom virtuellen Wissensraum zur Lernumgebung – Kooperatives Lernen als integrativer Ansatz für eine mediengestützte Bildung (From the Virtual Knowledge Space to a Learning Environment – Cooperative Learning as Integrative Approach to Educational Technology)
Authors: Geißler Sabrina , Hampel Thorsten , Keil-Slawik Reinhard
Published: August 2004

Klassische E-Learning-Umgebungen verkörpern vielfach eine ,Einbahnstraße des Lernens‛: Es werden hypermedial aufbereitete Materialien produziert, publiziert und rezipiert. Daneben gibt es Kommunikations- und Kooperationssysteme, die neue Formen der synchronen Interaktion zwischen Lehrenden und Lernenden ermöglichen. In beiden Ansätzen führt die Betonung der damit möglichen Zeit- und Ortsunabhängigkeit dazu, dass Funktionen und Materialien als isoliert zu nutzende Angebote wahrgenommen und umgesetzt werden. Mit dem vorliegenden Ansatz betonen wir dagegen nicht mehr die zeitliche und räumliche Unabhängigkeit, sondern die zeit- und ortsübergreifende Integration aller Prozesse, die im Rahmen eines Lehr- bzw. Lernarrangements auftreten. Dazu stellen wir das Konzept des virtuellen Wissensraums vor, der die nutzergesteuerte Integration unterschiedlicher Funktionsbereiche und Materialien ermöglicht. Da hierbei nicht die Einmalproduktion hochwertiger Materialien im Vordergrund steht, sorgt weiterhin ein multiperspektivischer Modulbegriff dafür, dass mediale Objekte mit unterschiedlichen Zeithorizonten und verschiedenen Rollenzuschreibungen bedarfsgerecht bearbeitet werden können. Die Umsetzung dieser Konzepte wird an einem praktischen Beispiel aus der universitären Lehre illustriert.
Die zehn wichtigsten Gender-Mainstreaming-Regeln bei der Gestaltung von Lernmodulen (The Ten Most Important Gender Mainstreaming Rules for Creating E-Learning Modules)
Authors: Wiesner Heike , Zorn Isabel , Schelhowe Heidi , Baier Barbara , Ebkes Ida
Published: August 2004

Der vorliegende Beitrag beschreibt Ergebnisse aus dem Begleitforschungsprojekt „Gender Mainstreaming medial“ im Programm NMB, an dem untenstehende Personen beteiligt waren. Neben Beratung, Begleitung und Evaluierung von 100 BMBF-Projekten war eine der Aufgaben die Entwicklung von Kriterien für Gender Mainstreaming (GM) in e-Learning-Angeboten. Diese sollten helfen, Grundlagen für Geschlechtergerechtigkeit sowohl in den Projekten als auch in den Lernplattformen und den darin eingelagerten Lernmodulen zu schaffen. Dazu wurden ein GM-Guideline (Wiesner et al. 2004) und ein GM-Styleguide (Wiesner et al. 2003) entwickelt. Außerdem wurden die 100 NMB-Projekte nach GM-Kriterien evaluiert, um BestPractice-Beispiele herauszuarbeiten. Ergebnis der Analyse war, dass es keinem Projekt gelungen ist, alle GM-Kriterien zu erfüllen. Es ist jedoch einigen Projekten gelungen, einzelne GM-Strategien in ihren Lernmodulen erfolgreich umzusetzen. Wir haben diese Aspekte gebündelt und in einem 10-Punkte-Plan für die Gestaltung von Lernmodulen zusammengefasst. Jede der zehn Regeln beschreibt einen zentralen Aspekt bei der genderbewussten Konzeption und Gestaltung von digitalen Lernmodulen. Drei von zehn dieser GM-Aspekte finden innerhalb dieses Artikels eine nähere Erläuterung.
“HistoBrick”: Mobile Edutainment into Descriptive Statistics („HistoBrick“: Mobiles Edutainment zur Deskriptiven Statistik)
Authors: Ströhlein Georg
Published: August 2004

Based on preceding work on a mobile learning scenario a mobile game like application, called “HistoBrick”, is being designed. It serves as a platform for exercises, assignments and self studies in combination with the higher education courseware on descriptive statistics. This paper focuses on the mobile application and ignores its embedding into a suitable Learning Management System (LMS). “HistoBrick” aims to provide a ubiquitous tool for learning about statistic distributions and their most important characteristic numbers. The didactical background is inspired by recent ideas about how learning works in the so-called constructivist setting, in general, and the findings of game-based learning, in particular.
Verbessern von Vorlesungen durch E-Learning Komponenten (Enriching Lectures through E-Learning Components)
Authors: Glowalla Ulrich , Glowalla Gudrun , Görlich Sascha
Published: August 2004

In diesem Beitrag zeigen wir, wie durch den flexiblen Einsatz von E-Learning Komponenten die Präsenzlehre an Universitäten bereichert werden kann. Wir konzentrieren uns dabei auf zwei große Vorlesungen mit jeweils mehreren hundert Teilnehmern, in die wir über ein Learning Management System verschiedene E-Learning Komponenten integrierten. Im Verlauf des Semesters kamen elektronisch verschickte und zu bearbeitende Studierfragen und Gruppenarbeiten, Online- und Offline-Wissenstests sowie das selbständige Erarbeiten von Vorlesungsinhalten anhand einer E-Lecture zum Einsatz. Unsere Ergebnisse zeigen, dass die Studierenden die zusätzlichen Angebote als sinnvolle Ergänzung der Vorlesung erlebten, den Lehrstoff aktiver bearbeiteten und auch bessere Lernleistungen erzielten.
Shadowing and absorption corrections of single-crystal high-pressure data
Authors: Katrusiak Andrzej
Published: August 2004

The effect of shadowing the sample crystal enclosed in the diamond-anvil high-pressure cell (DAC) by the gasket edges, i.e. by the walls of the high-pressure chamber, has been described for unrestricted data-collection procedures. A general vector formalism reveals new features of the shadowing and absorption corrections, depending on the primary beam-DAC-reflection configuration. The corrections apply to the data measured with conventional normal-beam-equatorial diffractometers, or with area-detectors. The simple vector approach optimizes computations and affords straightforward corrections of intensities. Feasibility of enhancing the resolution of numerical integration by applying fine grid divisions, has been discussed.