bluuebunny/crossref_metadata_2025 huggingface dataset:
Enantiomerically Pure Thrombin Inhibitors for Exploring the Molecular‐Recognition Features of the Oxyanion Hole
Authors: Schärer Kaspar , Morgenthaler Martin , Seiler Paul , Diederich François , Banner David W. , Tschopp Thomas , Obst‐Sander Ulrike
Published: October 2004

A new route via intermediate pseudoenantiomers was developed to synthesize racemic and enantiomerically pure new non‐peptidic inhibitors of thrombin, a key serine protease in the blood‐coagulation cascade. These ligands feature a conformationally rigid tricyclic core and are decorated with substituents to fill the major binding pockets (distal (D), proximal (P), selectivity (S1), and oxyanion hole) at the thrombin active site (Fig. 1). The key step in the preparation of the new inhibitors is the 1,3‐dipolar cycloaddition between an optically active azomethine ylide, prepared in situ from L‐(4R)‐hydroxyproline and 4‐bromobenzaldehyde, and N‐piperonylmaleimide (Scheme 1). According to this protocol, tricyclic imide (compounds (±)‐15‐(±)‐18 and (+)‐21) and lactam (compound (+)‐2) inhibitors with OH or ether substituents at C(7) in the proline‐derived pyrrolidine ring were synthesized to specifically explore the binding features of the oxyanion hole (Schemes 2–4). Biological assays (Table) showed that the polar oxyanion hole in thrombin is not suitable for the accommodation of bulky substituents of low polarity, thereby confirming previous findings. In contrast, tricyclic lactam (+)‐2 (Ki=9 nM, Ki(trypsin)/Ki(thrombin)=1055) and tricyclic imide (+)‐21 (Ki=36 nM, Ki(trypsin)/Ki(thrombin)=50) with OH‐substituents at the (R)‐configured C(7)‐atom are among the most‐potent and most‐selective thrombin inhibitors in their respective classes, prepared today. While initial modeling predicted H‐bonding between the OH group at C(7) in (+)‐2 and (+)‐21 with the H2O molecule bound in the oxyanion hole (Fig. 2), the X‐ray crystal structure of the complex of (+)‐21 (Fig. 7, b) revealed a different interaction for this group. The propionate side chain of Glu192 undergoes a conformational change, thereby re‐orienting towards the OH group at C(7) under formation of a very short ionic H‐bond (OH⋅⋅⋅−OOC; d(O⋅⋅⋅O)=2.4 Å). The energetic contribution of this H‐bond, however, is negligible, due to its location on the surface of the protein and the unfavorable conformation of the H‐bonded propionate side chain.
Preparation and Characterization of New Phosphonyl‐Substituted Imidazolium Ionic Liquids
Authors: Mu Zong‐gang , Zhou Feng , Zhang Shu‐xiang , Liang Yong‐min , Liu Wei‐min
Published: October 2004

A new series of diethoxyphosphinyl‐substituted imidazolium ‘room‐temperature ionic liquids’ (RTILs) were synthesized and characterized. The new compounds 1–12 (Table 1) were shown to have similar densities, but higher viscosities, than common ionic liquids. The new materials remain liquid over a broad temperature range, possess extremely low vapor pressures, display relatively high thermal stabilities (up to 325°), and decompose in a two‐step process. Analysis of the solid/liquid phase transition showed that all of the new RTILs possess low glass‐transition temperatures (Tg) associated with an intense change in molar heat capacity (ΔCpm).
Synthetic Studies Towards the Preparation of 2‐Benzyl‐2‐ hydroxybenzofuran‐3(2H)‐one, the Prototype of Naturally Occurring Hydrated Auronols
Authors: Löser Reik , Chlupacova Marta , Marecek Ales , Opletalova Veronika , Gütschow Michael
Published: October 2004

Various synthetic approaches were employed to prepare 2‐benzyl‐2‐hydroxybenzofuran‐3(2H)‐one (8), the prototype of naturally occurring auronols. While the base‐induced ring transformation of 3‐hydroxyflavanone (2) as well as the hydration of 2‐benzylidenebenzofuran‐3(2H)‐one (=aurone; 6) proved to be inappropriate, the hydrogenolytic epoxide‐ring opening of 2′‐phenylspiro[benzofuran‐2(3H),2′‐oxiran]‐3‐one (7), obtained from 6, represents an efficient method to afford the auronol 8.
Structure, Characterization, and Metal‐Complexation Properties of a New Tetraazamacrocycle Containing Two Phenolic Pendant Arms
Authors: Cui Xiuling , Calhorda Maria José , Costa Paulo J. , Delgado Rita , Drew Michael G. B. , Félix Vítor
Published: October 2004

The new tetraazamacrocycle 2 (=2,2′‐[[7‐Methyl‐3,7,11,17‐tetraazabicyclo[11.3.1]heptadeca‐1(17),13,15‐triene‐3,11‐diyl]bis(methylene)]bis(4‐bromophenol)) was synthesized and used as a ligand for different metal‐ion complexes. The X‐ray crystal structures of the complexes of the general formula [M(H‐2)]+NO$\rm{_{3}^{-}}$⋅MeOH (M=Ni2+, Zn2+), in which only one of the two pendant phenolic OH groups of 2 is deprotonated, were determined. In both complexes, the coordination environment is of the [5+1] type, the four N‐atoms of the macrocyclic framework defining a square‐planar arrangement around the metal center, with similar NiN and ZnN distances of 1.961(9) to 2.157(9) Å and 2.021(9) to 2.284(8) Å, respectively. In contrast, the MO distances are markedly different, 2.060(6) and 2.449(8) Å in the NiII complex, and 2.027(7) and 2.941(9) Å in the ZnII complex. The UV/VIS spectra of the NiII and CuII complexes with ligand 2, and the EPR spectra of the CuII system, suggest the same type of structure for the complexes in solution as in the solid state. Theoretical studies by means of density functional theory (DFT) confirmed the experimental structures of the NiII and ZnII complexes, and led to a proposal of a similar structure for the corresponding CuII complex. The calculated EPR parameters for the latter and comparison with related data support this interpretation. The singly occupied molecular orbital (SOMO) in these systems is mainly made of a d orbital of Cu, with a strong antibonding (σ*) contribution of the axially bound phenolate residue.
About a Practical Synthesis of Ambrox® from Sclareol: a New Preparation of a Ketone Key Intermediate and a Close Look at its Baeyer–Villiger Oxidation
Authors: Moulines Jean , Bats Jean‐Paul , Lamidey Anne‐Marie , Da Silva Nicole
Published: October 2004

The latest route to Ambrox® (1) starting from sclareol (2) proceeds through an oxy ketone 4 (Scheme 1). A new practical synthesis of the key intermediate 4 is described; it is equivalent to a partial oxidative degradation of sclareol (2) with peracetic and periodic acids (Scheme 2). The final product of the BaeyerVilliger oxidation of the oxy ketone 4 with commercial peracetic acid is decisively dependent on the reaction conditions because the expected acetate 9 reacts with any nucleophile, especially the peracid (Scheme 3). Furthermore, this acetate 9 is very prone to eliminative coupling (Scheme 4).
A New Approach to Nicotine: Symmetry Consideration for Synthesis Design
Authors: Ho Tse‐Lok , Kuzakov Eugene V.
Published: October 2004

A synthesis of nicotyrine (9), and hence formally racemic nicotine, was carried out by elaboration of the 1 : 1 adduct 2 of cycloocta‐1,5‐diene and chlorosulfonyl isocyanate (ClSO2NCO). Transformation of adduct 2 into carbamate 4 was followed by ozonolysis, tosylation, and NaH treatment, which led to pyrrolidinylpiperidinone 6. LiAlH4 Reduction, debenzylation, and aromatization yielded 2.
Simulated impacts of climate change and land‐clearing on runoff from a small Sahelian catchment
Authors: Séguis L. , Cappelaere B. , Milési G. , Peugeot C. , Massuel S. , Favreau G.
Published: October 2004

In the Sahel, there are few long‐term data series available to estimate the climatic and anthropogenic impacts on runoff in small catchments. Since 1950, land clearing has enhanced runoff. The question is whether and by how much this anthropogenic effect offsets the current drought. To answer this question, a physically based distributed hydrological model was used to simulate runoff in a small Sahelian catchment in Niger, from the 1950–1998 rain‐series. The simulation was carried out for three soil surface states of the catchment (1950, 1975 and 1992). The catchment is characterized by an increase in cultivated land, with associated fallow, from 6% in 1950 to 56% in 1992, together with an increase in the extent of eroded land (from 7 to 16%), at the expense of the savanna. Effects of climate and land use are first analysed separately: irrespective of the land cover state, the simulated mean annual runoff decreases by about 40% from the wet period (1950–1969) to the dry period (1970–1998); calculated on the 1950–1998 rainfall‐series, the changes that occurred in land cover between 1950 and 1992 multiplies the mean annual runoff by a factor close to three. The analysis of a joint climatic and anthropogenic change shows that the transition from a wet period under a ‘natural’ land cover (1950) to a dry period under a cultivated land cover (1992) results in an increase in runoff of the order of 30 to 70%. At the scale of a small Sahelian catchment, the anthropogenic impact on runoff is probably more important than that of drought. This figure for relative increase in runoff contributions to ponds, preferential sites of seepage to groundwater, is less than that currently estimated for aquifer recharge, which has been causing a significant continuous water table rise over the same period. Copyright © 2004 John Wiley & Sons, Ltd.
Long‐term final void salinity prediction for a post‐mining landscape in the Hunter Valley, New South Wales, Australia
Authors: Hancock G. R. , Wright A. , De Silva H.
Published: October 2004

Opencast mining alters surface and subsurface hydrology of a landscape both during and post‐mining. At mine closure, following opencast mining in mines with low overburden to coal ratios, a void is left in the final landform. This final void is the location of the active mine pit at closure. Voids are generally not infilled within the mines' lifetime, because of the prohibitive cost of earthwork operations, and they become post‐mining water bodies or pit lakes. Water quality is a significant issue for pit lakes. Groundwater within coal seams and associated rocks can be saline, depending on the nature of the strata and groundwater circulation patterns. This groundwater may be preferentially drawn to and collected in the final void. Surface runoff to the void will not only collect salts from rainfall and atmospheric fallout, but also from the ground surface and the weathering of fresh rock. As the void water level rises, its evaporative surface area increases, concentrating salts that are held in solution. This paper presents a study of the long term, water quality trends in a post‐mining final void in the Hunter Valley, New South Wales, Australia. This process is complex and occurs long term, and modelling offers the only method of evaluating water quality. Using available geochemical, climate and hydrogeological data as inputs into a mass‐balance model, water quality in the final void was found to increase rapidly in salinity through time (2452 to 8909 mg l−1 over 500 years) as evaporation concentrates the salt in the void and regional groundwater containing high loads of salt continues to flow into the void. Copyright © 2004 John Wiley & Sons, Ltd.
Hydrochemistry of groundwaters in a spa area of Korea: an implication for water quality degradation by intensive pumping
Authors: Kim Kangjoo , Koo Min‐Ho , Moon Sang‐Ho , Yum Byoung‐Woo , Lee Kwang‐Sik
Published: October 2004

A geochemical study was carried out in a small spa area (Onyang Spa, Korea) where intensive pumping of deep thermal groundwater (1 300 000 m3 year−1) is taking place. This has caused the deep fractures to lose their artesian pressure and the upper shallow fractures have been encroached by shallow, cold waters. To quantify the influence of long‐term heavy pumping on the quality of the geothermal water, groundwater sampling and chemical analysis, water‐level measurement, and well loggings were performed for the selected deep thermal wells and shallow cold wells. Chemical analysis results indicate a big contrast in water chemistry and origins between the two water types. Shallow groundwater shows a wider concentration ranges in solutes that are closely related to human activity, illustrating the water's vulnerability to contamination near the land surface. Plots of water chemistry as a function of fluoride reveal that the quality of the thermal water was greatly influenced by the shallow, cold groundwater and that intensive pumping of the deep thermal groundwater has caused the introduction of shallow groundwater into the deeper fractures. Although the deep and the shallow fractures were piezometrically separated to some extent, a mixing model based on fluoride and nitrate indicated that the cold‐water fractions in the thermal wells are up to 50%. This suggests that the thermal water is faced with water quality degradation by the downward flow of the shallow, cold water. Restriction on the total of all the pumpage permits per unit area is suggested to restore the artesian pressure of the deep thermal aquifer and to prevent cold‐water intrusion in the study area. Copyright © 2004 John Wiley & Sons, Ltd.
Novel markers for poor prognosis in head and neck cancer
Authors: Chin David , Boyle Glen M. , Williams Rebecca M. , Ferguson Kaltin , Pandeya Nirmala , Pedley Julie , Campbell Catherine M. , Theile David R. , Parsons Peter G. , Coman William B.
Published: October 2004

Head and neck cancer (HNSCC) is one of the most distressing human cancers, causing pain and affecting the basic survival functions of breathing and swallowing. Mortality rates have not changed despite recent advances in radiotherapy and surgical treatment. We have compared the expression of over 13,000 unique genes in 7 cases of matched HNSCC and normal oral mucosa. Of the 1,260 genes that showed statistically significant differences in expression between normal and tumor tissue at the mRNA level, the three top ranking of the top 5% were selected for further analysis by immunohistochemistry on paraffin sections, along with the tumor suppressor genes p16 and p53, in a total of 62 patients including 55 for whom >4‐year clinical data was available. Using univariate and multivariate survival analysis, we identified SPARC/osteonectin as a powerful independent prognostic marker for short disease‐free interval (DFI) (p < 0.002) and poor overall survival (OS) (p = 0.018) of HNSCC patients. In combination with other ECM proteins found in our analysis, PAI‐1 and uPA, the association with DFI and OS became even more significant (p < 0.001). Our study represents the first instance of SPARC as an independent prognostic marker in HNSCC.
Red meat consumption and risk of cancers of the proximal colon, distal colon and rectum: The Swedish Mammography Cohort
Authors: Larsson Susanna C. , Rafter Joseph , Holmberg Lars , Bergkvist Leif , Wolk Alicja
Published: October 2004

Although there is considerable evidence that high consumption of red meat may increase the risk of colorectal cancer, data by subsite within the colon are sparse. The objective of our study was to prospectively examine whether the association of red meat consumption with cancer risk varies by subsite within the large bowel. We analyzed data from the Swedish Mammography Cohort of 61,433 women aged 40–75 years and free from diagnosed cancer at baseline in 1987–1990. Diet was assessed at baseline using a self‐administered food‐frequency questionnaire. Over a mean follow‐up of 13.9 years, we identified 234 proximal colon cancers, 155 distal colon cancers and 230 rectal cancers. We observed a significant positive association between red meat consumption and risk of distal colon cancer (p for trend = 0.001) but not of cancers of the proximal colon (p for trend = 0.95) or rectum (p for trend = 0.32). The multivariate rate ratio for women who consumed 94 or more g/day of red meat compared to those who consumed less than 50 g/day was 2.22 (95% confidence interval [CI] 1.34–3.68) for distal colon, 1.03 (95% CI 0.67–1.60) for proximal colon and 1.28 (95% CI 0.83–1.98) for rectum. Although there was no association between consumption of fish and risk of cancer at any subsite, poultry consumption was weakly inversely related to risk of total colorectal cancer (p for trend = 0.04). These findings suggest that high consumption of red meat may substantially increase the risk of distal colon cancer. Future investigations on red meat and colorectal cancer risk should consider cancer subsites separately. © 2004 Wiley‐Liss, Inc.
In vitro culture of rat neuromicrovascular endothelial cells on polymeric scaffolds
Authors: Conconi Maria Teresa , Lora Silvano , Baiguera Silvia , Boscolo Elisa , Folin Marcella , Scienza Renato , Rebuffat Piera , Parnigotto Pier Paolo , Nussdorfer Gastone Giovanni
Published: October 2004

Polyphosphazenes are polymers possessing a skeleton composed of alternating phosphorous and nitrogen atoms, and two side‐moieties linked to each phosphorous atom. Polyphosphazenes with amino acid esters as side‐moieties are biocompatible and biodegradable polymers. Two polyphosphazenes, poly[bis(ethyl alanate) phosphazene] and poly[(ethyl phenylalanate)0.8(ethyl alanate)0.8(ethyl glycinate)0.4 phosphazene] (PPAGP) were synthesized, and processed to form small fibers. Their ability to support rat neuromicrovascular endothelial cell (EC) adhesion and growth has been studied, using poly(D,L‐lactic acid) as reference compound. Scanning electron microscopy revealed that both poly[bis(ethyl alanate) phosphazene] and PPAGP fibers were thinner than poly(D,L‐lactic acid) fibers, and possessed a more irregular and porous surface. All polymers increased EC adhesion, compared with polystyrene, but only polyphosphazenes were able to improve EC growth. The highest increase in EC proliferation was induced by PPAGP, which, as revealed by environmental scanning electron microscopy, was also able to induce ECs to arrange into tubular structures. The conclusion is drawn that PPAGP may provide the best scaffold for engineered blood vessels, because it promotes adhesion, growth, and organization of ECs into capillary‐like structures. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 669–674, 2004
Mediation of cadmium‐induced oxidative damage and glucose‐6‐phosphate dehydrogenase expression through glutathione depletion
Authors: Xu Jun , Maki Daisuke , Stapleton Susan R.
Published: October 2004

The effect of cadmium (Cd), a significant environmental contaminant, on the expression of glucose‐6‐phosphate dehydrogenase (G6PDH), has been investigated. G6PDH is the key rate‐limiting enzyme in the pentose pathway and the expression of its gene has been shown to be redox‐sensitive. We show that incubation of primary rat hepatocytes with Cd induces oxidative stress in a time‐ and concentration‐dependent manner as measured by increases in the cytotoxic parameters, lactate dehydrogenase (LDH) and lipid peroxidation (LPO). Significant increases in LDH leakage and LPO can be measured after 12 and 24 h, respectively, in the presence of 4 μM cadmium chloride. However, prior to significant increases in cytotoxic parameters, and within only 6 h of Cd treatment, significant decreases in reduced glutathione and increases in the expression of G6PDH as measured by mRNA levels and enzyme activity are observed. The signal protein MAP kinase (MAPK) is also induced by Cd within 6 h. Blocking the Cd induction of MAPK using the antioxidant N‐acetyl cysteine (10 mM) or Trolox (0.5 mM) or the MEK specific inhibitor PD098059 (20 μM) also blocks the Cd induction of G6PDH suggesting that MAPK is a signal protein involved in the redox regulation of this gene. © 2003 Wiley Periodicals, Inc. J Biochem Mol Toxicol 17:67–75, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10062
Hepatic enzymatic synthesis and hydrolysis of CoA esters of solvent‐derived oxa acids
Authors: Panuganti Sree D. , Penn Jill M , Moore Kathleen H.
Published: October 2004

Many ethylene glycol‐derived solvents are oxidized to xenobiotic alkoxyacetic acids (3‐oxa acids) by hepatic enzymes. The toxicity of these ubiquitous solvents has been associated with their oxa acid metabolites. For many xenobiotic carboxylic acids, the toxicity is associated with the CoA ester of the acid. In this study, related alkoxyacetic acids were evaluated as potential substrates for acyl‐CoA synthetases found in mitochondrial, peroxisomal, and microsomal fractions isolated from rat liver. Likewise, chemically synthesized oxa acyl‐CoAs were used as substrates for acyl‐CoA hydrolases associated with the same rat liver fractions. Activities of the xenobiotic oxygen‐substituted substrates were compared with analogous physiologic aliphatic substrates by UV–vis spectrophotometric methods. All of the solvent‐derived oxa acids were reasonable substrates for the acyl‐CoA synthetases, although their activity was usually less than the corresponding physiologic acid. Acyl‐CoA hydrolase activities were decreased compared with acyl‐CoA synthetase activities for all substrates, especially for the oxa acyl‐CoAs. These studies suggest that these xenobiotic carboxylic acids may be converted to reactive acyl‐CoA moieties which will persist in areas of the cell proximal to lipid synthesis, β‐oxidation, protein acylation, and amino acid conjugation. The interaction of these xenobiotic acyl‐CoAs with those processes may be important to their toxicity and/or detoxification. © 2003 Wiley Periodicals, Inc. J Biochem Mol Toxicol 17:76–85, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10063
Evaluation of toxic potential of captan: Induction of hsp70 and tissue damage in transgenic drosophila melanogaster (hsp70‐lacZ) Bg9
Authors: Nazir Aamir , Mukhopadhyay Indranil , Saxena D. K. , Siddiqui M. Saeed , Chowdhuri D. Kar
Published: October 2004

The study investigated the working hypothesis that a widely used fungicide captan exerts toxic effects on nontarget organisms. Transgenic Drosophila melanogaster (hsp70‐lacZ) was used as a model by assaying stress gene expression as an endpoint for cytotoxicity and also to evaluate whether stress gene expression is sufficient enough to protect and to prevent tissue damage against toxic insult of the chemical. The study was further extended to understand the effect of the pesticide on development, life cycle, and reproduction of the organism and finally to evaluate a concentration of the chemical to be nontoxic to the organism. The study showed that (i) captan causes cytotoxicity at and above 0.015 ppm; (ii) at 0.0015 ppm captan, absence of hsp70 expression in the exposed organism was evaluated as the concentration referred to as no observed adverse effect level (NOAEL) for Drosophila; (iii) emergence pattern of flies was affected only at the highest concentration of captan by 4 days, while hatching and survivorship were unaffected even at this concentration; (iv) reproductive performance was significantly affected only at 125.0 and 1250.0 ppm captan, while in the lower dietary concentrations no such deleterious effects were observed; (v) at 1250.0 ppm, hsp70 failed to protect the cells from toxicant assault after 48 h exposure, thus leading to tissue damage as revealed by Trypan Blue staining. The present study shows the cytotoxic potential of captan and further reveals the application of stress genes in determining NOAEL and its expression as bioindicator of exposure to environmental contaminants. © 2003 Wiley Periodicals, Inc. J Biochem Mol Toxicol 17:98–107, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10066
Detection of recipient’s cells in liver graft using antibodies to mismatched HLA class I antigens
Authors: Grassi Alberto , Susca Micaela , Ravaioli Matteo , Grazi Gian Luca , D’Errico Antonia , Bontadini Andrea , Zauli Daniela , Pinna Antonio , Bianchi Francesco B. , Ballardini Giorgio
Published: October 2004

Engraftment by recipient’s (R) cells has been already demonstrated in gender mismatched liver grafts using fluorescence in situ hybridization (FISH), with contrasting results concerning epithelial cells. Mismatch for human leukocyte antigen (HLA) class I (HLA-I) is quite common in patients with orthotopic liver transplantation (OLT). We thus aimed to assess whether monoclonal antibodies (MoAbs), currently employed in the HLA typing process, could be used to study the dynamics of R cells in liver grafts. A total of 50 frozen liver biopsies from 37 patients receiving a HLA mismatch liver were tested. Biopsies were obtained from 3 days to more than 360 days after OLT. Frozen sections of graft biopsies were stained using an immunoperoxidase technique with the proper MoAbs. In selected cases, a double immunofluorescence was also performed. Circulating R blood cells and sinusoidal cells were occasionally observed in liver biopsies obtained within 10 days after OLT and were commonly detected after 1 month. The number of sinusoidal cells continued to increase up to 6 months, as shown on serial biopsies. On the whole, R blood cells and R sinusoidal cells were detected in 86% and 82% of the biopsies, respectively. R hepatocytes and biliary cells were detected after 40 and 60 days after OLT, respectively, in 14% (hepatocytes), 8% (bile ducts), and 12% (proliferating bile ducts) of the biopsies. R hepatocytes presented as single cells or groups of few cells; their number was lower than 1% and apparently did not increase with time after OLT. In conclusion, it is possible to detect R cells in liver graft using MoAbs to specific mismatched HLA-I alleles. R sinusoidal cells start to appear after 10 days and are commonly observed after 1 month; bile duct cells and hepatocytes appear later and their number does not increase with time. Engraftment by R epithelial cells seems to be less important than previously reported. (Liver Transpl 2004;10:1406-1414.)
One-year morbidity after donor right hepatectomy
Authors: Rudow Dianne LaPointe , Brown Robert S. , Emond Jean C. , Marratta Douglas , Bellemare Sarah , Kinkhabwala Milan
Published: October 2004

Live donors are becoming an increasingly important source of donor organs in liver transplantation; however, long-term functional aspects of recovery from donor right hepatectomy are unknown. We analyzed donor outcomes at 1-year follow-up. We performed a single-center retrospective analysis of 70 right hepatectomy donors. Six-week and 1-year postoperative follow-up results were compared to preoperative baseline values. Ultrasonography was performed in all donors at 6 weeks and as clinically indicated. All donors were alive and well at the end of the study period. Of 66 right hepatic donors, only 22 (32%) were fully compliant with a 1-year follow-up visit. All those not compliant were contacted by phone. All complications except 1 (late finding of portal vein thrombosis) occurred in the perioperative (90-day) period. The incidence of bile leak was 4.3%, incisional hernia 20%, and autologous transfusion 1.0%. There were no aborted procedures. In those compliant with full 1-year follow-up, total bilirubin, aspartate aminotransferase, and alanine aminotransferase were normal in 97%. A total of 5 donors were noted to have persistence of asymptomatic thrombocytopenia beyond the perioperative period (90 days). These were investigated with Doppler sonography. Sonography was unremarkable in 3 of the 5, while 2 had abnormal findings: splenomegaly alone in 1, and splenomegaly with portal vein thrombosis in the other. Magnetic resonance angiography was performed in both, and the patient with portal vein thrombosis underwent endoscopy, which failed to reveal varices. Neither has clinical portal hypertension. Both remain asymptomatic albeit with stable thrombocytopenia. In conclusion, the majority of complications after donor right hepatectomy occur in the perioperative period. Later findings may include asymptomatic thrombocytopenia, with an incidence possibly as high as 23%, though the significance of this finding remains uncertain. Larger-scale studies are needed to confirm the true incidence and clinical significance of persistent thrombocytopenia in the donor hepatectomy population. Strategies to improve compliance with 1-year follow-up visits need to be developed. (Liver Transpl 2004;10:1428-1431.)
Thermisch hoch beanspruchte Verschleißschutzschichten
Authors: Winkelmann R. , Deppe E.
Published: October 2004

Eine Entwicklung von Zusatzwerkstoffen für Anwendungen bei tribologisch – thermischer Beanspruchung wird am Beispiel der Paarung Schnecke‐Zylinder von Spritzgießmaschinen vorgestellt. In den Untersuchungen werden sowohl Zusatzwerkstoffe für Plasmapulverauftragschweißungen als auch vergleichend hierzu PM‐HIP‐Legierungen berücksichtigt. Die geschweißten und über den HIP‐Prozeß hergestellten Proben werden vergleichend auf einer Verschleißprüfmaschine bei Temperaturen bis zu 700 °C untersucht. Es erfolgen Messungen des Abtrages und der wirkenden Kräfte. Beurteilt werden sowohl reine Cobaltbasislegierungen als auch Co‐WC‐ und Co‐Mo‐WC‐Legierungen. Insbesondere gilt es, die Sinnfälligkeit der Anwendung sphärischer Carbide zu bewerten. Die Verschleißuntersuchungen sind gekoppelt an metallografische und metallurgische Betrachtungen.
Grundlagenuntersuchungen zum Einsatz umweltverträglicher Tribosysteme beim Zerspanen und in der Kaltumformung
Authors: Klocke F. , Maßmann Th. , Grams J.
Published: October 2004

Im Rahmen des Sonderforschungsbereiches 442 „Umweltverträgliche Tribosysteme”︁ (SFB 442) der Deutschen Forschungsgemeinschaft (DFG) ist der Lehrstuhl für Technologie der Fertigungsverfahren am WZL mit den Teilprojekten B5 „Zerspanung”︁ und B6 „Kaltumformung”︁ vertreten. Ziel beider Teilprojekte ist es, die bisher von den Zwischenstoffen geleisteten tribologischen Funktionen – Werkstofftrennung und Verschleißreduzierung – durch den Einsatz von PVD‐Beschichtungen auf die Werkzeugoberflächen zu übertragen. Dazu werden die tribologischen Bedingungen bei den Zerspanverfahren Drehen und Bohren sowie bei den Verfahren Kaltmassivumformen und Feinschneiden durch analytische Betrachtungen, Finite‐Elemente‐Simulationen und Experimente bestimmt. Aus den tribologischen Bedingungen werden Anforderungen an die Eigenschaften von neu zu entwickelnden Hartstoffschichten abgeleitet. An einem innerhalb des SFB 442 entwickelten Stift‐Scheibe‐Tribometer, mit dem die Bedingungen in der Zerspanung und in der Kaltumformung nachgebildet werden können, werden die neu entwickelten Tribosysteme getestet. Es wird gezeigt, dass eine Hartstoffschicht den Verschleißerscheinungen, die bei Wegfall der tribologischen Funktionen der Fluide auftreten, guten Widerstand bieten kann. Die Basisversuche Drehen, Bohren, Kaltmassivumformung und Feinschneiden dienen dann zur Validierung der im Tribometer gewonnenen Erkenntnisse.
Ortsaufgelöste Messung mikrotribologischer Eigenschaften mehrphasiger Oxidkeramiken mit der Rastersondenmikroskopie
Authors: Ziebert C. , Zum Gahr K.‐H.
Published: October 2004

In der Oberfläche von monolithischer Aluminiumoxidkeramik wurden durch lasergestütztes Umschmelzen und Zugabe von Hafniumoxid (HfO2), Wolfram (W), oder einer Mischung von Zirkonoxid (ZrO2), Wolframkarbid (WC) und Titannitrid (TiN) mehrphasige Gefüge eingestellt. Mit Hilfe der Rastersondenmikroskopie wurden Eigenschaften und das tribologische Verhalten verschiedener zweiter Phasen der mehrphasigen Al2O3‐Keramiken in Kontakt mit Si‐Spitzen auf der Mikro‐/Nanoskala untersucht. Aus den mikrotribologischen Ergebnissen zur Reibungszahl, Einsprungkraft und Abrisskraft in Abhängigkeit von der Luftfeuchte wurden Folgerungen für die tribologischen Wirkmechanismen einzelner Phasen abgeleitet. Es zeigte sich ein starker Einfluss von weichen Oberflächenfilmen auf die mikrotribologischen Wechselwirkungen.
Lasermodifizierte Al2O3‐ und ZTA‐Keramik für reversierend beanspruchte Gleitkomponenten unter Mangelschmierung
Authors: Peter E. , Zum Gahr K.‐H.
Published: October 2004

In Hinblick auf mediengeschmierte Gleitsysteme, wie beispielsweise hermetisch dichte Kolbenpumpen, wurden tribologische Untersuchungen an kommerziellen und lasergestützt modifizierten Al2O3‐Keramiken durchgeführt. Um die tribologischen Eigenschaften im mediengeschmierten, reversierenden Gleitkontakt unter Bedingungen der Mischreibung zu verbessern, wurde eine Al2O3‐ und eine Al2O3‐ZrO2‐Keramik (ZTA) in einer Randschichtdicke von 300 bis 400 μm laserlegiert. Als Medien wurden destilliertes Wasser, 1‐molare Natronlauge und 1‐molare Salzsäure eingesetzt. In den ungeschmierten und mediengeschmierten Versuchen in einem Ring/Platte‐Labortribometer zeigten die Paarungen mit den randschichtmodifizierten Keramiken einen deutlich höheren Verschleißwiderstand als die Paarungen mit den handelsüblichen Keramiken. Sowohl die Reibung als auch der Verschleißwiderstand wurden stark durch die Art des Mediums unter den gewählten Versuchsbedingungen beeinflusst.
Einfluss der Temperatur auf das tribologische Verhalten von DLC‐Schichten
Authors: Klaffke D. , Hartelt M. , Brand J. , Brand C. , Wittorf R.
Published: October 2004

Diamantähnliche Kohlenstoffschichten (DLC) zeichnen sich durch ein sehr günstiges Reibungs‐ und Verschleißverhalten aus. Auf vielen Werkzeugen und hochbelasteten Bauteilen ist DLC daher bereits erfolgreich im Einsatz. In naher Zukunft wird die Bedeutung dieser Schichten als Oberflächenschutz in tribologischen Systemen weiter ansteigen.

Wie viele Applikationsbeispiele zeigen, ist die Leistungsfähigkeit von DLC als Schicht zur Verringerung von Reibung und Verschleiß zwar groß, weist aber auch Grenzen auf. Vor allem bei höheren Temperaturen (> 300 °C) treten Strukturveränderungen oder sogar Oxidationsvorgänge auf, die auch die tribologischen Eigenschaften der Schichten verschlechtern können.

Reibungs‐ und Verschleißuntersuchungen (Schwingungsverschleiß) von DLC‐Schichten wurden im Temperaturbereich von 25 °C bis 250 °C durchgeführt und zeigen ein schnelleres Durchreiben der Schicht bei höheren Temperaturen. Die „Lebensdauer”︁ der Schichten wird mit zunehmender Prüftemperatur reduziert. Einsatzgrenzen für DLC‐Schichten können abgeleitet werden.
Neuartige Polyetheretherketon (PEEK)‐Beschichtungen für hohe tribologische Beanspruchungen
Authors: Oster F. , Haupert F. , Friedrich K. , Müller M. , Bickle W.
Published: October 2004

Im Rahmen der hier vorgestellten Arbeiten wurde ein hochtemperaturbeständiger Thermoplast‐Compound für Gleitlageranwendungen mit herausragenden tribologischen Eigenschaften entwickelt. Ausgehend von einer reinen Polyetheretherketon (PEEK)‐Matrix wurden unterschiedliche Mischungen mit konventionellen Füllstoffen, wie Kohlenstoff‐Fasern (CF), Polytetrafluorethylen‐Partikeln (PTFE) oder Graphit‐Pulver, hergestellt. Darüber hinaus kamen auch kleinste Zinksulfid (ZnS)‐ und Titandioxid (TiO2)‐Partikel mit einem mittleren Durchmesser von 300 nm zum Einsatz. Es zeigte sich, dass bei gleichzeitiger Verwendung der Füllstoffe CF, Graphit, ZnS und TiO2 mit definierten Füllstoffgehalten die größte tribologische Leistungssteigerung gefunden wurde. Der entsprechende Compound (PEEK6) wurde gegen den Referenzwerkstoff PEEK4 (etablierter Hochleistungs‐Compound für tribologische Anwendungen) bei erhöhten Temperaturen und unterschiedlichen Lastkollektiven (Variation von Gleitgeschwindigkeit und Normalkraft) untersucht. Hierbei zeigte sich eine deutliche Überlegenheit von PEEK6 gegenüber PEEK4 bei höheren Prüftemperaturen. Weitere Vorteile von PEEK6 ergaben sich bei erhöhten Lastkollektiven, d. h. der Kombination aus höheren Gleitgeschwindigkeiten und Normalkräften.
Kavitationserosion von Ingenieurkeramik in Abhängigkeit von Medium und Oberflächenbearbeitung
Authors: Dulias U. , Zum Gahr K.‐H.
Published: October 2004

In Hinblick auf den Einsatz in schnelllaufenden Pumpen wurde das kavitationserosive Verhalten ausgewählter Oxid‐ und Nichtoxidkeramiken untersucht. Die Schwingungskavitation wurde in einem Laborprüfstand unter Anlehnung an die ASTM Norm G 32‐92 in destilliertem Wasser und Isooktan erzeugt. Dabei wurden Proben mit fein‐ und grobgeschliffenen sowie polierten Oberflächen aus verschiedenen Al2O3‐Keramiken und einer SSiC‐Keramik eingesetzt. Untersuchungsgegenstand war der Einfluss des Werkstoffgefüges, der Oberflächenqualität und die Art des flüssigen Mediums. Die Ergebnisse zeigten, dass mit verbesserter Oberflächenqualität, geringerer Korngröße sowie tendenzmäßig mit höherer Risszähigkeit der Widerstand gegen Kavitationserosion zunahm. Sowohl bei den handelsüblichen Al2O3‐Keramiken als auch der SSiC‐Keramik ergaben Versuche in dest. Wasser höhere Erosionsgeschwindigkeiten als in Isooktan.
Charakterisierung des Verschleißverhaltens von Formeinsatz‐Werkstoffen für das Mikro‐Pulverspritzgießen
Authors: Schneider J. , Iwanek H. , Zum Gahr K.‐H.
Published: October 2004

Die Herstellung von keramischen und metallischen Mikrokomponenten in Mittel‐ und Großserie durch Mikro‐Pulverspritzgießen gefüllter Formmassen mit abrasiven keramischen oder metallischen Partikeln stellt hohe Anforderungen an die Verschleißbeständigkeit der eingesetzten Formeinsatz‐Werkzeuge. Im Rahmen dieser Forschungsarbeiten wurde daher das Verschleißverhalten verschiedener legierter und unlegierter Stähle, galvanisch abgeschiedenen Nickels sowie einer Messinglegierung in einem speziellen Einspritz‐Modellprüfstand unter Beanspruchung durch ZrO2‐, Al2O3‐ und Stahl‐Formmasse charakterisiert. Die geringsten Verschleißbeträge wurden dabei jeweils an Prüfkörpern aus dem einphasigen Nickel ermittelt. Die mehrphasigen, hochlegierten Stähle zeigten im Vergleich zum Nickel bei Beanspruchung durch keramische Formmasse um einen Faktor von bis zu drei höhere Verschleißbeträge. Die Ergebnisse der Untersuchungen zeigten, dass neben den Eigenschaften der Formmasse (u. a. Anteil, Größe, Form und Härte der keramischen bzw. metallischen Partikel) insbesondere die Gefügehomogenität und weniger die Härte das Verschleißverhalten der Formeinsatz‐Materialien beeinflusste.
Influence of Environment, Temperature and Chemical Composition on the Microstructural Deterioration of CrNi Steels during Friction
Authors: Pinto H. , Pyzalla A. R. , Hübner W. , Aßmus K.
Published: October 2004

Austenitic stainless steels are materials commonly used in cryotechnology. At extremely low temperatures these steels still exhibit good mechanical properties along with sufficient ductility. However high mechanical loads combined with low temperatures may induce martensitic transfomation. Martensite leads to brittle failure of machine components, which operate at cryogenic temperatures, and disturbs the superconductive effect due to its ferromagnetism.

The aim of the present work was the investigation of the influence of temperature, environment and loading parameters on the martensitic transformation and the microstructural deterioration of three austenitic CrNi steels. X‐ray diffraction and microscopy studies were carried out on samples worn at room temperature in air with different humidities, at 77 K in LN2, at 20 K in LH2 and at 4.2 K in LHe. Results show that martensitic transformation in FeCrNi alloys during friction can be supressed by a slightly increased Ni‐content. A decrease of temperature causes changes in the deformation mechanisms and results in embrittlement. In liquid hydrogen a marked deterioration of the microstructure was observed.
Solid‐state amidization and imidization reactions in vapor‐deposited poly(amic acid)
Authors: Anthamatten Mitchell , Letts Stephan A. , Day Katherine , Cook Robert C. , Gies Anthony P. , Hamilton Tracy P. , Nonidez William K.
Published: October 2004

The condensation polymerization of 4,4′‐oxydianiline with pyromellitic dianhydride for the formation of poly(amic acid) and the subsequent imidization for the formation of polyimides were investigated for films prepared with vapor‐deposition polymerization techniques. Fourier transform infrared spectroscopy, thermal analysis, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry of films at different temperatures indicated that additional solid‐state polymerization occurred before imidization. The experiments revealed that, upon vapor deposition, poly(amic acid) oligomers formed that had a number‐average molecular weight of about 1500 Da. Between 100–130 °C, these chains underwent an additional condensation reaction and formed slightly higher molecular weight oligomers. Calorimetry measurements showed that this reaction was exothermic [enthalpy of reaction (ΔH) ∼ −30 J/g] and had an activation energy of about 120 kJ/mol. The experimental ΔH values were compared with results from ab initio molecular modeling calculations to estimate the number of amide groups formed. At higher temperatures (150–300 °C), the imidization of amide linkages occurred as an endothermic reaction (ΔH ∼ +120 J/g) with an activation energy of about 130 kJ/mol. The solid‐state kinetics depended on the reaction conversion as well as the processing conditions used to deposit the films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5999–6010, 2004
Identification of monovinyl tripropionic acid porphyrins and metabolites from faeces of patients with hereditary coproporphyria by high‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry
Authors: Danton Malcolm , Lim Chang Kee
Published: October 2004

The original article to which this Erratum refers was published in Rapid Commun. Mass Spectrom. 2004; 18: 2309–2316
Minimization of carbon addition during derivatization of monosaccharides for compound‐specific δ13C analysis in environmental research
Authors: Gross Simone , Glaser Bruno
Published: October 2004

Little is known about the δ13C composition of monosaccharides representing the largest carbon reservoir in the biosphere. The main reason for this might be that monosaccharides have to be derivatized prior to gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analyses and that a large isotopic correction is necessary for the carbon that has to be added to the original molecule during derivatization, resulting in large uncertainty of the calculated δ13C values of individual monosaccharides. The amount of added derivatization carbon is twice (alditol acetates) or even three times (trimethylsilyl (TMS) derivatives) as high as the amount of the original monosaccharide carbon. In addition, isotope fractionation occurs during acetylation. Therefore, the objectives of this study were (i) to minimize carbon addition during derivatization for GC/C/IRMS measurements of monosaccharides in soil and sediment samples and (ii) to quantify improvements in accuracy and precision of the final results. Minimization of carbon addition was accomplished by derivatization with methylboronic acid (MBA) and TMS thereafter (MBA method). Monosaccharides derivatized with the MBA method instead of TMS reduced the number of added carbon atoms from 2.2–2.7 to 0.3–0.8 per sugar carbon atom. Although the precision of GC/C/IRMS measurements with both methods is comparable (about 0.3‰), δ13C values of an internal standard indicated that the newly developed MBA method is about 2‰ more accurate than the TMS method. δ13C comparison between soil samples that differed only slightly in their bulk carbon isotope signature showed that the MBA method is better in proving these small differences on a significant level. Total precision of the whole MBA method including all analytical and calculation steps is better by a factor of almost three than the TMS method. Copyright © 2004 John Wiley & Sons, Ltd.
Analysis of urinary nucleosides. IV. Identification of urinary purine nucleosides by liquid chromatography/electrospray mass spectrometry
Authors: Dudley Edward , Lemière Filip , Van Dongen Walter , Tuytten Robin , El‐Sharkawi Salah , Brenton A. Gareth , Esmans Eddy L. , Newton Russell P.
Published: October 2004

Modified urinary nucleosides are potentially invaluable in cancer diagnosis. High‐performance liquid chromatography (HPLC) was combined with full scan mass spectrometry (MS), tandem mass spectrometry and MSn analysis in order to identify purine nucleosides purified from urine. UV peaks evident in the chromatogram were examined by the various mass spectrometric techniques and adenosine, 1‐methyladenosine, xanthosine, N1‐methylguanosine, N2‐methylguanosine, N2,N2‐dimethylguanosine, N2,N2,N7‐trimethylguanosine, inosine, and 1‐methylinosine were each identified in the urine samples from cancer patients. The benefits of the use of LC/MS compared with HPLC alone are discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Avoidance of a giant component in half the edge set of a random graph
Authors: Bohman Tom , Frieze Alan , Wormald Nicholas C.
Published: October 2004

Let e1, e2, … be a sequence of edges chosen uniformly at random from the edge set of the complete graph Kn (i.e., we sample with replacement). Our goal is to choose, for m as large as possible, a subset E ⊆ {e1, e2, …, e2m}, |E| = m, such that the size of the largest component in G = ([n], E) is o(n) (i.e., G does not contain a giant component). Furthermore, the selection process must take place on‐line; that is, we must choose to accept or reject on ei based on the previously seen edges e1, …, ei−1.

We describe an on‐line algorithm that succeeds whp for m = .9668n. A sequence or events En is said to occur with high probability (whp) if limn → ∞ Pr(En) = 1. Furthermore, we find a tight threshold for the off‐line version of this question; that is, we find the threshold for the existence of m out of 2m random edges without a giant component. This threshold is m = c*n where c* satisfies a certain transcendental equation, c* ∈ [.9792, .9793]. We also establish new upper bounds for more restricted Achlioptas processes. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 25, 2004
Perfect matchings in random bipartite graphs with minimal degree at least 2
Authors: Frieze Alan
Published: October 2004

We show that a random bipartite graph with n+n vertices and cn random edges, and minimum degree at least two, has a perfect matching whp. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 26, 2005
Zur Geschichte der Biegesteifigkeit bei Verbundstützen
Authors: Bergmann Reinhard
Published: October 2004

Das vereinfachte Bemessungsverfahren für Verbundstützen hat im Laufe der Historie der Vorschriftenentwicklung einige Modifikationen erfahren, die sich besonders in der Festlegung der Biegesteifigkeit der Stütze niedergeschlagen haben. Diese Modifikationen sind durch ein geändertes Sicherheitskonzept, durch harmonisierte Definitionen der Festigkeiten und durch eine geänderte Erfassung des Einflusses der Imperfektion begründet.Die Entwicklungsstufen werden beschrieben und exemplarisch verglichen. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Erdbebensicherung durch Structural Control
Authors: Dorka Uwe E.
Published: October 2004

Für die Erdbebensicherung von Bauwerken geeignete Structural Control‐Konzepte, wie BI‐, HYDE‐, TENDON‐ und PAGODA‐Systeme, beruhen auf unter Erdbeben günstig wirkenden Starrkörpermechanismen, deren Bewegungen durch passive oder semi‐aktive Geräte kontrolliert werden. Sie sind damit nicht auf “natürliche” Mechanismen, wie sie in herkömmlichen Tragwerken entstehen, angewiesen und können so sicherer, effizienter und wirtschaftlicher gestaltet werden. Sie sind vielfältig einsetzbar und bieten vor allem bei der Sanierung große Vorteile. Ihre Anwendung erfordert allerdings ein Umdenken bei Konstruktion und Berechnung und für Bauingenieure ungewohnte Methoden zur Sicherheitsabschätzung. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Zum Tragverhalten von Ankerschienen unter ermüdungsrelevanten Einwirkungen
Authors: Hanenkamp Werner , Güreş Selçuk
Published: October 2004

Die Ergebnisse experimenteller Untersuchungen zum Tragverhalten von warmgewalzten, gezahnten Ankerschienen der Ausführung 38/23 ST unter ermüdungsrelevanten Einwirkungen (vorwiegend nichtruhende Beanspruchung) werden vorgestellt. Der Einfluß des umgebenden Betons auf das dynamische Tragverhalten sowie die Größe der Abminderung der Ermüdungstragfähigkeit bei Laststellungen unter Ausnutzung von Mindestendüberständen wird erläutert. Aus Schwingversuchen im Zugschwellbereich mit verschiedenen Lastrichtungen werden Interaktionsbeziehungen für nichtruhende Beanspruchungen entwickelt. Auf der Basis von Schwingversuchen (Zugschwellbereich) mit konstanten Unterlasten wird ein Vergleich der zur Zeit gültigen Bemessung für ermüdungsrelevante Einwirkungen mit einem Bemessungsvorschlag für Dübelbefestigungen vorgenommen. Ausgangspunkt der Untersuchungen waren Fragestellungen, die sich im Nachgang der allgemeinen bauaufsichtlichen Zulassung für die warmgewalzte gezahnte Ankerschiene 38/23 ergaben. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)