bluuebunny/crossref_metadata_2025 huggingface dataset:
Known and potential functions for the SLP‐76 adapter protein in regulating T‐cell activation and development
Authors: Clements James L.
Published: March 2003

The hematopoietic adapter protein SLP‐76 is a critical component of multiple biochemical signaling ‘circuits’ in T cells that integrate proximal signaling events initiated by ligation of the T‐cell receptor (TCR) into more distal pathways. Given the important role ascribed to TCR signaling in directing the outcome of thymocyte selection, it seems likely that SLP‐76 may also function in signaling pathways that ultimately impact the establishment of the peripheral T‐cell repertoire. It is generally accepted that the peripheral T‐cell repertoire is selected in large part during T‐cell development in the thymus. Molecular interactions between the TCR and self‐peptide/major histocompatibility complexes expressed on thymic stromal elements dictate the fate of developing thymocytes. Thymocyte survival and further maturation (positive selection) require an active signal delivered to the cell as a consequence of TCR ligation. This raises the intriguing question of how a thymocyte can, for a narrow window of developmental time, obtain responsiveness to self while maintaining tolerance to these same determinants upon export to the periphery. This article reviews the current literature describing SLP‐76‐dependent signaling pathways in mature T cells and developing thymocytes. A potential role for this critical signaling intermediate in integrating signals leading to positive and negative selection of the peripheral T‐cell repertoire is also discussed.
The Ras/MAPK cascade and the control of positive selection
Authors: Alberola‐Ila José , Hernández‐Hoyos Gabriela
Published: March 2003

Immature double positive (DP) thymocytes bearing a T cell receptor (TCR) that interacts with self‐major histocompatibility complex (MHC) molecules receive signals that induce either their differentiation (positive selection) or apoptosis (negative selection). Furthermore, those cells that are positively selected develop into two different lineages, CD4 or CD8, depending on whether their TCRs bind to MHC class II or I, respectively. Positive selection therefore involves rescue from the default fate (death), lineage commitment, and progression to the single positive (SP) stage. These are probably temporally distinct events that may require both unique and overlapping signals. Work in the past several years has started to unravel the signaling networks that control these processes. One of the first pathways identified as important for positive selection was Ras and its downstream effector, the Erk mitogen‐activated protein kinase (MAPK) cascade. In this review we examine the factors that connect the TCR to the Ras/Erk cascade in DP thymocytes, as well as what we know about the downstream effectors of the Ras/Erk cascade important for positive selection. We also consider the possible role of this cascade in CD4/CD8 lineage development, and the possible interactions of the Ras/Erk cascade with Notch during these cell fate determination processes.
Kupffer cell depletion by CI2MDP‐liposomes alters hepatic cytokine expression and delays liver regeneration after partial hepatectomy
Authors: Meijer Catharina , Wiezer Marinus J. , Diehl Anna M. , Yang Shi‐Qi , Schouten Hylke J. , Meijer Sybren , Van Rooijen Nico , Van Lambalgen Antonie A. , Dijkstra Christine D. , Van Leeuwen Paul A. M.
Published: March 2003

Abstract: Background: Although Kupffer cells (KCs) are capable of producing important growth‐stimulating cytokines, their role in liver regeneration following partial hepatectomy (PH) remains poorly understood. Methods: In the present study liver regeneration was studied after KC‐depletion by intravenous administration of liposome‐encapsulated dichloromethylene‐diphosphonate (Cl2MDP), a method known to physically eliminate KCs. Furthermore, splenectomy was performed one week prior to PH to exclude the effect of Cl2MDP‐liposomes on macrophage populations in the spleen. Results: KC‐depletion was confirmed in cryostat liver sections stained with the monoclonal antibody ED2, a marker for resident tissue macrophages. Forty‐eight hours after PH, the cumulative hepatocyte DNA synthesis, as determined in liver sections by the hepatocyte bromodeoxyuridine labeling index, was significantly decreased in KC‐depleted rats when compared to control‐rats. The weight of the remnant liver, expressed as a percentage of the initial liver weight, was significantly less at 96 h after PH in KC‐depleted rats. KC‐depletion abolished the hepatic interleukin‐6 (IL‐6) and interleukin‐10 (IL‐10) mRNA synthesis and decreased hepatic expression of tumor necrosis factor‐α (TNF‐α), hepatocyte growth factor (HGF) and transforming growth factor‐β1 (TGF‐β1) mRNA after PH, as was assessed by reverse‐transcriptase polymerase chain reaction (RT‐PCR). Moreover, at 4 h after PH the systemic release of IL‐6 was significantly decreased in KC‐depleted rats. Conclusion: We conclude that KCs are important for hepatocyte regeneration after PH. Delayed liver regeneration in KC‐depleted rats can be explained, at least in part, by an imbalanced hepatic cytokine expression, thereby suppressing important growth‐stimulating cytokines.
HLA class II genotypes associated with chronic hepatitis C virus infection and response to α‐interferon treatment in Poland
Authors: Wawrzynowicz‐Syczewska Marta , Underhill James A. , Clare Michael A. , Boron‐Kaczmarska Anna , McFarlane Ian G. , Donaldson Peter T.
Published: March 2003

Abstract: Aims/Background: Recent evidence suggests that spontaneous clearance of hepatitis C virus (HCV) may be associated with the HLA DQB1*0301 allele but there is still some debate over the role of other alleles and HLA haplotypes in HCV infection. As this may best be resolved by studying genetically different populations, we have investigated HLA class II‐encoded susceptibility and resistance to HCV infection in a relatively sedentary population of patients from northwestern Poland. Methods: The distributions of HLA class II DRB1, DQA1, DQB1 and DPB1 alleles were determined by standard PCR‐protocol in 129 unrelated patients with chronic hepatitis C (anti‐HCV and HCV‐RNA positive) and 103 healthy unrelated racially‐matched control subjects. Fifty‐five patients were treated with α‐interferon (5 MIU thrice weekly for 6 months) out of whom 29 showed a complete response and 26 were non‐responders. Results: A significantly reduced frequency of the DQB1*0301 allele in the patients was observed (24.0% vs. 38.8%; p=0.015). Additionally, two different DR‐DQ haplotypes were found to be associated with chronic HCV infection: DRB1*1501‐DQA1*01‐DQB1*0602 (24.0% vs. 12.6%; p=0.027) and DRB1*0701‐DQA1*0201‐DQB1*02 (31.8 vs. 12.6%; p=0.0006), the latter difference being most pronounced in those patients who responded to α‐interferon treatment (41.4% vs. 12.6%; p=0.00048). Conclusions: The results confirm the negative association between chronic HCV and DQB1*0301 and identify two novel genetic associations. In particular, the DRB1*0701‐DQA1*0201‐DQB1*02 haplotype is associated with both chronic infection and response to α‐interferon. Interestingly, the same haplotype is reportedly associated with non‐response to hepatitis B vaccination.
Inhibition of lipopolysaccharide‐induced I‐κB degradation and tumor necrosis factor‐α expression by dimethyl‐4,4′‐dimethoxy‐5,6,5′,6′‐dimethylene dioxybiphenyl‐2,2′‐dicarboxylate (DDB): minor role in hepatic detoxifying enzyme expression
Authors: Kim Sang Geon , Kim Hye Jung , Choi Sung Hee , Ryu Ji Yeun
Published: March 2003

Abstract: Aims/Background: Dimethyl‐4,4′‐dimethoxy‐5,6,5′,6′‐dimethylene dioxybiphenyl‐2,2′‐dicarboxylate (DDB) is active against a variety of hepatotoxins and has been used as a curative agent for patients with acute and chronic viral hepatitis. Effects of DDB on the expression of xenobiotic‐metabolizing enzymes and on nuclear factor‐κB (NF‐κB) activation and tumor necrosis factor‐α (TNF‐α) production by lipopolysaccharide (LPS), an endotoxin involved in inflammatory responses, were examined in rats and in RAW264.7 cells to investigate mechanistic aspects. Methods: Expression of hepatic cytochrome P450s, microsomal epoxide hydrolase and glutathione S‐transferases was determined by immunoblot and Northern blot analyses. Activation of hepatic NF‐κB and I‐κBα degradation was assessed by gel mobility shift and immunoblot analyses, respectively. LPS‐induced TNF‐α expression was monitored in rats and in RAW264.7 cells by enzyme‐linked immunosorbent assay and/or reverse transcription‐polymerase chain reaction analysis. Results: DDB failed to alter the expression of hepatic cytochrome P450 1A and 2C11, microsomal epoxide hydrolase and glutathione S‐transferases in rats with slight inhibition of P450 2E1 expression, but induced P450 2B1/2. Pretreatment of rats with DDB prevented LPS‐induced hepatic I‐κBα degradation and the resultant NF‐κB activation, and inhibited the LPS‐induced plasma TNF‐α protein and hepatic TNF‐α mRNA expression in a dose‐dependent manner. LPS‐induced I‐κBα degradation and TNF‐α production were also inhibited by DDB in RAW264.7 cells, which was consistent with the results in rats. Conclusions: The present study demonstrated that DDB may inhibit inflammatory responses in association with reduction of NF‐κB activation through prevention of I‐κBα degradation and subsequent TNF‐α production, but not with modulation of the detoxifying enzyme expression.
Improved response to ribavirin interferon combination compared with interferon alone in patients with type 4 chronic hepatitis C without cirrhosis
Authors: Koshy Abraham , Marcellin Patrick , Martinot Michele , Madda John P.
Published: March 2003

Abstract: Response to treatment with alpha interferon with or without concomitant ribavirin varies according to the viral genotype in patients with chronic hepatitis C. Aim: This study was undertaken in order to determine the response of genotype 4 chronic hepatitis C to interferon and ribavirin combination compared to interferon alone in patients without cirrhosis. Methods: Fifty‐two patients were given interferon alone at a dose of 5 million units, 3 times a week and another 60 patients were administered with interferon combined with ribavarin (1000–1200 mg/day) for 24 weeks. Sustained biochemical response was defined as normal ALT, 6 months after end of therapy. Sustained virologic response was defined as negative HCV RNA, 6 months after the end of therapy. Results: Only 10/52 (19%) patients showed sustained biochemical response after interferon alone, while 31/60 (52%) showed sustained biochemical response after interferon combined with ribavirin (p<0.01). Only 4/52 (8%) patients showed sustained virologic response after interferon alone, while 25/60 (42%) showed sustained virologic response after interferon combined with ribavirin (p<0.001). Conclusion: These results show that patients with chronic hepatitis due to hepatitis C virus type 4 show a poor response to interferon alone but a better response to interferon combined with ribavirin.
Early down‐regulation of cytochrome P450 3A and 2E1 in the regenerating rat liver is not related to the loss of liver mass or the process of cellular proliferation
Authors: Starkel Peter , Laurent Stéphanie , Petit Martine , Van Den Berge Véronique , Lambotte Luc , Horsmans Yves
Published: March 2003

Abstract: Aims/Background: Conflicting data have been reported concerning the modification of cytochrome P450 expression in the regenerating liver. Ligation of branches of the portal vein (PBL) perfusing 70% of the liver parenchyma, which produces regeneration and atrophy within the same liver, constitutes an ideal model to study the relative specificity of the early events in the regenerating liver and their relationship to the loss of liver mass. Methods: In this PBL model and in sham models, we studied the expression and the metabolic activities of two major cytochromes, CYP3A and CYP2E1, and the expression of inducible nitric oxide synthase protein (iNOS). They were simultaneously measured in the atrophying and regenerating liver lobes following PBL using Western Blot and HPLC methods. Results: The metabolic activities of both cytochromes were transiently and simultaneously down‐regulated in the regenerating and atrophying lobes during the first 2–5 h after PBL. No significant modification was observed at the protein level. In contrast, iNOS protein was significantly induced in both lobes. Similar results were observed after sham operation. Conclusions: The reduction of these CYP activities in both lobes after PBL and in sham livers suggests that other mechanisms than the regenerating process itself or the reduction of the liver mass might account for such down‐regulation during the early phase of liver regeneration. The activation of nitric oxide (NO) and/or pro‐inflammatory cytokine production provides clues to pathways liable to affect the CYP activities in the regenerating liver.
Interferon‐associated retinopathy in a uniform regimen of natural interferon‐α therapy for chronic hepatitis C
Authors: Saito Hidetsugu , Ebinuma Hirotoshi , Nagata Hiroshi , Inagaki Yasutaka , Saito Yoshimasa , Wakabayashi Kanji , Takagi Tamako , Nakamura Mitsuyasu , Katsura Hiroshi , Oguchi Yoshihisa , Ishii Hiromasa
Published: March 2003

Abstract: Background/Aims: The development of retinal lesions induced by a uniform regimen of interferon‐α therapy for chronic hepatitis C was prospectively investigated. Methods: Eighty‐one patients received 6 mega units of natural interferon‐α intramuscularly daily for 2 weeks and then 3 times a week for 22 weeks. The total dose of interferon‐α administered was uniformly 478 mega units per patient. Two expert ophthalmologists prospectively examined the patients for retinal lesions before, during and after the therapy. Results: Retinopathy was not found in comparison groups or any of the patients before treatment. In total 34.6% (28/81) of the patients showed cotton‐wool spots or minor retinal hemorrhage, or both lesions, during therapy, but these lesions were reversed during or after interferon therapy. The occurrence rates of cotton‐wool spots alone, retinal hemorrhage alone and both lesions were 13.6% (11/81), 6.2% (5/81), and 14.8% (12/81), respectively. The appearance of retinopathy did not correlate with patients’ background including viral loads and response to the therapy, but was more frequently found in older patients and patients with hypertension and/or diabetes mellitus; disappearance of retinopathy was more prolonged than in patients without these complications. Almost all the lesions appeared 2–4 months after the start of the therapy, and the severity of the lesions did not differ between patients with and without hypertension and/or diabetes mellitus. Conclusion: Although it is not clear if interferon‐associated retinopathy occurs in a dose‐dependent manner, the present study shows a standard pattern of the occurrence of retinopathy in patients with chronic hepatitis C receiving a uniform dosage of natural interferon‐α.
Immunohistochemical analysis of atypical ductular reaction in the human liver, with special emphasis on the presence of growth factors and their receptors
Authors: Kiss Andras , Schnur Janos , Szabó Zsuzsa , Nagy Peter
Published: March 2003

Abstract: Aims/Background: The objective of this study was to characterize the expression of transforming growth factor‐alpha/epidermal growth factor receptor, hepatocyte growth factor/c‐met, transforming growth factor‐beta/Type I‐II transforming growth factor‐beta receptors, stem cell factor, urokinase plasminogen activator, smooth muscle actin, CD34 and alpha‐fetoprotein in human liver samples with (sub)massive necrosis of different etiology containing atypical ductular reaction. Methods: Their presence was studied by immunohistochemistry on paraffin‐embedded tissue sections. Results: Transforming growth factor‐alpha and ‐beta, hepatocyte growth factor and their receptors were demonstrated in the ductules; additionally stem cell factor and urokinase plasminogen activator were also expressed. The atypical ductules were surrounded by smooth muscle actin‐positive activated stellate cells. Conclusion: These phenotypic similarities confirm that the atypical ductules in the human liver may be equivalent of oval cells in the rat liver, which are regarded as the progeny of stem cells. That is, the atypical ductular proliferation may correspond to a stem cell‐fed regenerative process.
Neuronal nitric oxide synthase immunoreactivity in the guinea‐pig liver: distribution and colocalization with neuropeptide Y and calcitonin gene‐related peptide
Authors: Esteban Francisco J. , Jiménez Ana , Fernández A. Patricia , Del Moral M. Luisa , Sánchez‐López Ana M. , Hernández Raquel , Garrosa Manuel , Pedrosa Juan A. , Rodrigo José , Peinado M. Ángeles
Published: March 2003

Abstract: Aims/Background: The innervation pattern of the guinea‐pig liver is similar to that of the human liver. However, many aspects of the distribution of the neuronal isoform of the enzyme nitric oxide synthase (nNOS) in the guinea‐pig liver and its colocalization with neuropeptides remain to be elucidated. Methods: The distribution of nNOS was studied in fixed guinea‐pig liver by light microscopic immunohistochemistry. Confocal analysis was used to determine its colocalization with neuropeptide Y (NPY) or calcitonin gene‐related peptide (CGRP). Results: nNOS‐immunoreactive (nNOS‐IR) nerves were observed in relation to hilar and interlobar vessels and in Glisson’s capsule. A few nNOS‐IR ganglia were observed in the extrahepatic bile duct and close to the interlobar portal triads. In addition, nNOS‐IR fibers were located in the interlobular portal triads and pervading the parenchyma. Moreover, nNOS‐IR nerves were demonstrated for the first time in the larger central veins and in the hepatic vein. nNOS‐NPY and nNOS‐CGRP colocalizations were detected in the fibromuscular layer of the bile duct and periductal plexus, respectively. Conclusions: These results support the phylogenetic conservation of the nNOS‐IR hepatic innervation and its possible contribution to the regulation of hepatic blood flow and certain hepatic functions.
Allergic cholestatic hepatitis and exanthema induced by metamizole: verification by lymphocyte transformation test
Authors: Herdeg C. , Hilt F. , Büchtemann A. , Bianchi L. , Klein R.
Published: March 2003

Abstract: We report about a 66‐year‐old‐male patient who was hospitalized with generalized exanthema and increase of liver enzymes after intake of metamizole because of flue‐like symptoms. Despite initial high dose steroids, disease activity persisted, and therefore liver biopsy was performed. Histology revealed acute hepatitis with perivenular non‐bridging confluent necrosis and granuloma formation consistent with drug‐induced hepatitis. A metamizole‐induced process was suspected. Lymphocyte transformation test confirmed the sensitization of the patient's lymphocytes to metamizole and three of its four metabolites (4‐methylaminoantipyrine, 4‐acetylaminoantipyrine and 4‐formylaminoantipyrine). Other drugs could be excluded with high probability. In the follow‐up, the general condition of the patient improved, and liver enzymes decreased under treatment with steroids. Thus, we conclude that in this patient metamizole has induced an allergic reaction not only of the skin but also of the liver. To our knowledge, an allergic cholestatic hepatitis caused by metamizole has been reported only once in literature.
Magnetic resonance spectroscopy: anin vivotool for monitoring cerebral injury in SIV‐infected macaques
Authors: Greco J.B. , Sakaie K.E. , Aminipour S. , Lee P.L. , Chang L.L. , He J. , Westmoreland S. , Lackner A.A. , Gonzalez R.G.
Published: March 2003

Abstract: The purpose of our study was to demonstrate the feasibility of usingin vivoproton Magnetic Resonance Spectroscopy (MRS) to monitor the brain manifestations of SIV infection in the macaque model of AIDS. Previous spectroscopy work on macaque brain tissue andin vivowork in humans is reviewed to provide the motivation and context for this study. We collected 34 MRS data sets on 14 uninfected rhesus macaques. From this data, we demonstrate that we are capable of detecting changes similar to those observed in human MRS studies for most metabolites using less than 10 animals. The juvenile macaques utilized in this study demonstrate age‐related changes in the levels ofN‐acetyl aspartate (NAA), a neuronal marker. The quantity and distribution of neurochemicals in the macaque are found to be slightly, but significantly, different than in the human.
‘Round robin’ project on the estimation of slag viscosities
Authors: Mills Kenneth C. , Chapman Lindsay , Fox A. B. , Sridhar S.
Published: March 2003

A “round robin” project has been carried out to determine the accuracy and reliability of various models used to estimate the viscosities of industrial slags. The 21 participants were divided into measurement suppliers and modelling participants. Reference materials were issued to the measurement suppliers to check the validity of the viscosity data supplied. A data base of viscosity‐temperature‐composition data was established for 8 different categories of slags. Chemical compositions were issued to the different modelling participants and the predicted viscosities were compared with calculated values. For mould fluxes, the global % errors associated with the various models were: modified Iida (25), Riboud (30), Gupta (35), NPL (37). For non‐fluoride slag systems, the Ling Zhang, KTH and modified Iida models all performed well.
Arsenic removal from blister copper by soda injection into melts
Authors: Kucharski Marian
Published: March 2003

Soda injection into a blister is one of the most important operations in the copper refining processing. The aim of this work is to determine optimal parameters of a technology for arsenic removal from anode copper by use of soda (Na2CO3) injected into a molten copper bath by submerged tuyeres. Results of the work reveal that the rate of reaction between soda and arsenic is very high and sodium arsenate Na3AsO4 is formed. These findings have been used to work out a table, which gives the amount of soda to be used in the process as a function of refined copper quantity and arsenic content. The second part of this work is to demonstrate the use of nitrogen as a carrier gas for soda injected into the blister for arsenic removal. An application of neutral gases in this process is beneficial, and results in energy conservation.
Hot ductility of an Fe‐10%Ni alloy during penetration of copper
Authors: Hansson Karin , Droujevski Mikhail , Fredriksson Hasse
Published: March 2003

Today's available theories for hot crack formation are based on the fact that hot cracks are formed in the presence of liquid films in the interdendritic areas or at the grain boundaries, which are exposed to tensile stress. Copper is well known to cause hot shortness in steels. In order to study how the liquid embrittles the material, high‐temperature tensile tests were performed at two strain rates during the penetration of liquid copper into Fe‐10%Ni. The penetration distance was measured in samples that were exposed to strain without fracturing. The ductility (area reduction), strain and ultimate tensile stress were determined. Microprobe analysis was performed on the fractured samples. The transition temperature of ductility was found at 1400–1450°C without copper penetration whereas it occurred at 1025–1078°C during the penetration of copper, i.e. copper starts to embrittle at a temperature below its melting point. The microprobe measurements showed that the diffusion rate of copper into Fe‐10%Ni was enhanced when the lattice was strained. The results are discussed in terms of a new theory concerning vacancy formation and condensation as the dominating mechanism for hot crack formation during solidification.
Experimental investigation and thermodynamic description of the Cr‐Si‐Ti system
Authors: Du Yong , Schuster Julius C.
Published: March 2003

This paper provides a consistent thermodynamic data set for the Cr‐Si‐Ti system and its whole reaction scheme via experimental investigation and thermodynamic modeling. Alloys were prepared by arc melting of cold‐pressed pellets and annealing at 800 °C for 44 days and at 1000 °C for 21 day. Water‐quenched samples were analyzed by using X‐ray diffraction (XRD) and differential thermal analysis (DTA) techniques. The incipient melting points along the isopleth Cr5Si3– Ti5Si3 were measured by using the Pirani technique. The temperatures for 9 invariant reactions involving liquid phase below 1500 °C were accurately measured. The isothermal sections at 800 and 1000 °C and the isopleth Cr5Si3– Ti5Si3 were determined. The optimal thermodynamic data set for the Cr‐Si‐Ti system obtained by considering the present experimental results and reliable literature data describes these experimental data very well. This description predicts, for temperatures above 1500 °C, the existence of a continuous series of solid solutions between βCr5Si3 and Ti5Si3, having a melting point maximum substantially above the melting point of binary Ti5Si3. More work is needed for experimental confirmation of these predictions.
In‐situ observation of slag penetration into MgO refractory
Authors: Mukai Kusuhiro , Tao Zainan , Goto Kiyoshi , Li Zushu , Takashima Toshiyasu
Published: March 2003

The behavior of slag penetration into MgO refractory was investigated by combining in‐situ X‐ray observation with microstructural analysis of the samples after penetration experiments. The following results are obtained. The slag penetrates rapidly into the refractory, reacting with MgO particles in the refractory. The slag penetrates unevenly into the refractory with uneven pore size in a route like a tree, firstly along the main route (the surface of large MgO particles), and then extending to the branch route, while evenly into the refractory with even pore size. The rate of slag penetration increases with increasing pore radius and apparent porosity of the refractory, T · Fe concentration in the slag and temperature, and with decreasing the slag basicity (C/S ratio). In the case of the Al2O3‐bearing slag, the rate of slag penetration is less than that of Al2O3‐free slag in the initial stage. The penetration also stops much earlier than that of the Al2O3‐free slag, and then the penetration height remains almost constant. In the initial stage of penetration, the penetration height is proportional to the square root of penetration time. Slag penetration is deduced as stopping due to the following: (1) the melting point and viscosity of the penetrated slag increase, and the surface tension of the penetrated slag decreases with decreasing the FetO concentration in the penetrated slag consumed by the reaction between FetO and MgO particles; (2) in the 10mass% Al2O3‐bearing slag, the pore size in the refractory is reduced by the spinel formed on the pore surface by the reaction between Al2O3 in the penetrated slag and MgO particles in the refractory.
An alternative way for evaluating the deformation of MnS inclusions in hot rolling of steel
Authors: Luo Chunhui , Ståhlberg Ulf
Published: March 2003

The behavior of MnS inclusions during flat hot rolling of steel has been studied. Experiments were carried out in a four‐high mill. The workpiece was up to a nominal reduction in height of 85% in four passes, at rolling temperatures of 700–1200°C with interpass reheating. The relative plasticity and orientation of inclusions were quantitatively assessed by means of an image‐processing tool. Finite element analyses were performed in order to scrutinize the concept of ‘relative plasticity’, which is based on dimensional change of the inclusion. Furthermore, inclusion reorientation is discussed.
Mathematical model to simulate the temperature and composition distribution inside the flux layer of a continuous casting mould
Authors: Neelakantan Viswanathan Nurni , Sridhar Seetharaman , Mills K. C. , Sichen Du
Published: March 2003

A model is presented to predict the mass transport and heat transfer in a continuous casting mould flux bed. Physically consistent micromodels for carbon burning, evaporation of volatiles and thermophysical properties in the mould flux layer have been combined with a one‐dimensional finite‐difference model of the continuous casting mould flux bed. The sensitivity of the model to bed height, flux consumption rate, carbon burning and powder particle size is investigated for a mould flux composition corresponding to an industrial casting powder.
Activity measurement of liquid Ga‐In‐Te alloys by emf method with stabilized zirconia
Authors: Katayama Iwao , Yamazaki Kisao , Nakano Motohiro , Iida Takamichi
Published: March 2003

Electromotive force of galvanic cells with zirconia solid electrolytes was measured to determine the activity of gallium in liquid Ga‐In‐Te alloys in the temperature range of 1000 to 1200 K along 3 psuedobinary lines of (InyTe1−y)‐Ga where y= 0.25, 0.50 and 0.75. The mixture of Ga and Ga2O3 was used as a reference electrode. The activity curves of Ga are very complicated at 1073 K. Isoactivity curves at 1073 K in the ternary Ga‐In‐Te alloys were derived by combining the activity data of Ga‐In and Ga‐Te alloys. Using Darken's equation, 2 binary data of Ga‐In and Ga‐Te and ternary data in this study, ΔGXS at 1073 K were derived. The results were compared with those from 3 model calculations proposed by Toop, Kohler and Chou to show better agreement between the experimental values and those by Toop's and Chou's models.
Ferrosilicon magnesium production
Authors: El‐Faramawy Hoda , Eissa Mamdouh , Mattar Taha , Fathy Ayman , Ghali Saeed
Published: March 2003

The production of ferrosilicon magnesium by using carbon as a reducing agent in an electric arc furnace leads to serious problems owing to its high working temperature and the high vapour pressure of magnesium. On the other hand, the high cost of using aluminium in the production process and contamination of the produced alloy with aluminium makes this process undesirable. The silicothermic process seems to be the most preferable technique for producing ferrosilicon magnesium. The aim of this study is to investigate the different parameters controlling the ferrosilicon magnesium alloy production by the silicothermic process and to investigate a technique for the production process by the immersion of magnesium metal in molten ferrosilicon. Two techniques have been developed to produce ferrosilicon magnesium alloy. In the first, local calcinated dolomite ore was reduced either by the silicothermic or the aluminosilicothermic process. The reducing agents used were either ferrosilicon or a mixture of ferrosilicon and aluminium, respectively. The produced magnesium reacts with excess ferrosilicon to form magnesium silicide (Mg2Si). The amount of reducing agent and the type of added fluxing materials (limestone, fluorspar, bauxite and quartzite) are the main factors that have been investigated and the optimum conditions for obtaining the highest magnesium recovery have been determined. In the second technique, magnesium metal was immersed in molten ferrosilicon using a proper technique for the protection of magnesium. In the pilot plant experimental heats for the production of ferrosilicon magnesium, the highest magnesium recovery using a reduction technique was found to be 13.8%, where in the immersion technique, a higher magnesium recovery up to 77% was achieved. Furthermore, the study of the production cost of both techniques revealed that the immersion technique is more economical compared to the reduction one in producing the ferrosilicon magnesium alloy. The magnesium metal immersion in molten ferrosilicon has been successfully tested on an industrial scale to produce ferrosilicon magnesium alloy containing 5% Mg with high magnesium recovery of 89%.
The effect of living plants on root decomposition of four grass species
Authors: Van Der Krift Tanja A. J. , Kuikman Peter J. , Berendse Frank
Published: March 2003

We tested whether living plant roots of Holcus lanatus and Festuca ovina can affect the decomposition rate of dead roots of Holcus lanatus, Festuca rubra, Anthoxanthum odoratum and Festuca ovina. Moreover, we investigated whether this effect is dependent on the decomposing root species or the nitrogen supply during the growth of the roots. The selected perennial grass species are typical of grassland habitats in a range from high to low nitrogen availability: H. lanatus, F. rubra, A. odoratum and F. ovina. Seedlings of these species were homogeneously labelled with 14CO2 for eight weeks. Plants were grown on soil at two nitrogen levels: one without additional nitrogen and one with nitrogen addition (14 g N m−2).  At the start of the decomposition experiment 14C labelled roots were separated from soil and incubated in litterbags (mesh width 1 mm) in fresh soil. These 14C labelled roots were left to decompose for 19 weeks in an open greenhouse in soil planted with H. lanatus or F. ovina and in unplanted soil. After the incubation period, the decomposition of the 14C labelled roots of the four species was measured. The mass and 14C losses from the dead roots were calculated and the living plant biomass and C, N and P contents of the living plants were measured.  Living plant roots of F. ovina had positive effects on the decomposition rate of F. ovina root litter, but dead A. odoratum roots from the N fertilized treatment decomposed slower in the presence of living F. ovina plants. It seems likely that living plants like F. ovina exude carbon compounds that stimulate the growth of soil microbes and thereby increase dead root decomposition and mineralization. Root decomposition rates differed among the species. We found no evidence to support our hypothesis that dead roots of high fertility species (i.e. H. lanatus and F. rubra) decompose faster than dead roots of low fertility species (i.e. A. odoratum and F. ovina). In unplanted soil, the mass loss and total 14C loss from A. odoratum dead roots were higher than those from H. lanatus, F. rubra and F. ovina dead roots. Dead roots of F. ovina lost less mass and total 14C than dead roots of H. lanatus.
Structure of tropical river food webs revealed by stable isotope ratios
Authors: Jepsen David B. , Winemiller Kirk O.
Published: March 2003

Fish assemblages in tropical river food webs are characterized by high taxonomic diversity, diverse foraging modes, omnivory, and an abundance of detritivores. Feeding links are complex and modified by hydrologic seasonality and system productivity. These properties make it difficult to generalize about feeding relationships and to identify dominant linkages of energy flow. We analyzed the stable carbon and nitrogen isotope ratios of 276 fishes and other food web components living in four Venezuelan rivers that differed in basal food resources to determine 1) whether fish trophic guilds integrated food resources in a predictable fashion, thereby providing similar trophic resolution as individual species, 2) whether food chain length differed with system productivity, and 3) how omnivory and detritivory influenced trophic structure within these food webs. Fishes were grouped into four trophic guilds (herbivores, detritivores/algivores, omnivores, piscivores) based on literature reports and external morphological characteristics. Results of discriminant function analyses showed that isotope data were effective at reclassifying individual fish into their pre‐identified trophic category. Nutrient‐poor, black‐water rivers showed greater compartmentalization in isotope values than more productive rivers, leading to greater reclassification success. In three out of four food webs, omnivores were more often misclassified than other trophic groups, reflecting the diverse food sources they assimilated. When fish δ15N values were used to estimate species position in the trophic hierarchy, top piscivores in nutrient‐poor rivers had higher trophic positions than those in more productive rivers. This was in contrast to our expectation that productive systems would promote longer food chains. Although isotope ratios could not resolve species‐level feeding pathways, they did reveal how top consumers integrate isotopic variability occurring lower in the food web. Top piscivores, regardless of species, had carbon and nitrogen profiles less variable than other trophic groups.
Optimal infection strategies: should macroparasites hedge their bets?
Authors: Fenton A. , Hudson P. J.
Published: March 2003

Despite considerable research into the mechanisms that lead to the persistence of parasites, the huge diversity of macroparasite transmission strategies observed both within and among species has yet to be explained. This may be because questions of parasite persistence are typically addressed at the population level, even though observed transmission rates are determined by infection events at the level of the individual parasite. To help overcome this disparity, a simple model is developed to explore the optimal infection strategy for a macroparasite under a range of selection pressures. The model calculates the fitness of the parasite by considering explicitly the probability of the individual infective stages surviving and infecting. The optimal strategy is highly sensitive to the rate of host availability and, considering the parasite's fitness, it is often preferable to have sub‐maximal infectivity to maximise survival during periods of host absence. An important finding is that when parasites are faced with unpredictable conditions such as the time of host availability, the optimum strategy may be to produce offspring that differ in their infection strategies. By spreading the risk in this way, known as bet hedging, parasites can increase the chances that at least some of their offspring will infect successfully. This potential for variation in infection strategies has not been considered explicitly before and may have wide reaching implications for current epidemiology theory.
Effects of light and nitrogen on morphological plasticity of the mossCalliergonella cuspidata
Authors: Bergamini Ariel , Peintinger Markus
Published: March 2003

In a short‐term experiment we studied the effects of increased light and nitrogen (N) availability on the mossCalliergonella cuspidataby cutting vascular plants and adding nitrogen in a calcareous fen in the mountainous region of central Switzerland.  Shoots ofCalliergonellagrowing in plots with reduced vascular plant competition showed smaller increments in length of the main axis and produced shorter offshoots, but showed higher branching densities at the main axis, higher number of offshoots and higher dry mass per unit length.  Although the growth forms of pleurocarpous bryophytes are quite different from stolon‐ and ramet‐producing clonal vascular plants, the overall morphological responses to changing light levels are very similar and, at least in part, comparable to the ‘spacer and branching’ strategy exhibited by some stolon‐bearing vascular plants. The observed morphological plasticity ofCalliergonellawould in principle allow for foraging of heterogeneously distributed resources.  Nitrogen supply, on the other hand, had no effects on either dry mass or shoot morphology ofCalliergonella. Moreover, interactions between the effects of removal of vascular plants and increased nutrient supply on biomass and shoot morphology ofCalliergonelladid not occur. This could be explained by the short duration of the experiment. However, since above‐ground biomass of vascular plants was increased by the nutrient supply, it cannot be excluded that in the long run, increased N inputs will have serious secondary consequences onCalliergonella, e.g. due to heavy shading by vascular plants.
Interactions between common buzzard Buteo buteo and goshawk Accipiter gentilis: trade‐offs revealed by a field experiment
Authors: Krüger Oliver
Published: March 2003

I examined the behavioural interactions between common buzzard Buteo buteo and goshawk Accipiter gentilis and their effects on buzzard breeding success and brood defence with a two‐year field experiment using dummies and playback calls. A priori I showed through an extensive nest site analysis that there is considerable nesting habitat overlap between the two species and hence potential for interspecific competition for prime nesting habitat. Buzzards had a significantly lower breeding success when presented with a goshawk dummy compared to control broods but there was no effect of buzzard dummies on reproductive success. Buzzards failing with their breeding attempt tended to select another nest site while successful buzzards more frequently used the same nest again. Buzzard pairs were less often attacked by common crows Corvus corone while exposed to goshawk dummies compared to buzzard dummies. The decision to desert a nest seems to be a trade‐off between predation risk on the one hand and protection against crows on the other. Goshawks proved far more aggressive against an intraspecific dummy than buzzards. Buzzards adjusted their level of brood defence against both intra‐ and interspecific dummies according to the age of offspring but not offspring number, with an increasing brood defence level with increasing offspring age. Thus the behaviour of buzzards towards goshawks is a result of a complex system of trade‐offs between predation risk, competition for prime nesting habitat and protection from crows on which brood value acts as a temporal modifier.
Host plant and natural enemy impact on cereal aphid competition in a seasonal environment
Authors: Gonzáles Wilfredo L. , Fuentes‐Contreras Eduardo , Niemeyer Hermann M.
Published: March 2003

Competition between phytophagous insects could be mediated by differential impact of natural enemies or by induced changes in host plant quality. The interaction between the aphids Sipha flava and Rhopalosiphum maidis on the shared host plant, Sorghum halepense, was evaluated during the fall and spring seasons in the presence or absence of natural enemies in a garden experiment. During the fall, S. flava was negatively affected by R. maidis in all treatments. However, during the spring season, S. flava was not affected by R. maidis when natural enemies were excluded, and positively affected by R. maidis with natural enemies present. Rhopalosiphum maidis was negatively affected by S. flava during the fall and spring seasons under all treatments. Laboratory experiments demonstrated that changes in host plant quality induced by S. flava attack and the presence of the parasitoid Lysiphlebus testaceipes negatively affected R. maidis, but not S. flava. Under abiotic conditions simulating fall and spring (lower temperature and daylength in the fall than in the spring), S. flava showed lower performance than R. maidis under “fall” conditions, and both aphid species showed similar life history traits under “spring” conditions. For S. flava, the time to the first reproduction and longevity were longer, and the nymphal production was lower, under “fall” conditions than under “spring” conditions. Our results showed that S. flava is benefited when R. maidis and the parasitoid L. testaceipes are present but the abiotic conditions are not adverse.
Using body size to predict perceptual range
Authors: Mech Stephen G. , Zollner Patrick A.
Published: March 2003

We examined the relationship between body size and perceptual range (the distance at which an animal can perceive landscape elements) for a group of forest‐dwelling rodents. We used previously published data on orientation ability at various distances for three sciurid species (gray squirrel, fox squirrel and chipmunk) and one murid species (white‐footed mouse) to build a predictive model. We found a significant positive relationship between perceptual range and body mass. Although this model was built using a 15.5 m high horizon, we used this relation to predict the perceptual range of root voles (3.9–4.3 m) orienting towards a 0.5 m high horizon which was consistent with other empirical work suggesting a value of something less than 5 m. This model illustrates a relationship between perceptual range and body size and can be used to develop starting points for future investigations of perceptual range for similar organisms.
Functional redundancy in ecology and conservation
Authors: Rosenfeld Jordan S.
Published: March 2003

Multiple studies have shown that biodiversity loss can impair ecosystem processes, providing a sound basis for the general application of a precautionary approach to managing biodiversity. However, mechanistic details of species loss effects and the generality of impacts across ecosystem types are poorly understood. The functional niche is a useful conceptual tool for understanding redundancy, where the functional niche is defined as the area occupied by a species in an n‐dimensional functional space. Experiments to assess redundancy based on a single functional attribute are biased towards finding redundancy, because species are more likely to have non‐overlapping functional niches in a multi‐dimensional functional space. The effect of species loss in any particular ecosystem will depend on i) the range of function and diversity of species within a functional group, ii) the relative partitioning of variance in functional space between and within functional groups, and iii) the potential for functional compensation (degree of functional niche overlap) of the species within a functional group. Future research on functional impairment with species loss should focus on identifying which species, functional groups, and ecosystems are most vulnerable to functional impairment from species loss, so that these can be prioritized for management activities directed at maintaining ecosystem function. This will require a better understanding of how the organization of diversity into discrete functional groups differs between different communities and ecosystems.
A model of pollinator‐mediated gene flow between plant populations with numerical solutions for bumblebees pollinating oilseed rape
Authors: Cresswell J. E. , Osborne J. L. , Bell S. A.
Published: March 2003

We present a model that predicts the level of gene flow mediated by animal pollinators from a source population to a sink population. The model requires specification of three elements: (1) the paternity that originates from a single flower, the paternity shadow; (2) the mean number of flowers that pollinators visit during stays in the sink population, the residence; (3) the proportion of pollinators arriving at the sink that carry pollen from the source population. Provided that pollinators visit enough flowers in the sink to exhaust the paternity shadows from the source, the general results are that gene flow is inversely proportional to the mean pollinator residence in the sink population, and is proportional to the fraction of pollinators arriving with pollen from the source. These results are used to propose explanations for two of the widely observed patterns in gene flow among plant populations. Numerical solutions to the model are derived using experimentally determined values of elements (1) and (2) that represent bumblebees, Bombus spp., visiting agricultural fields of oilseed rape, Brassica napus L. In B. napus, the paternity shadow attenuates rapidly over approximately 20 recipient flowers. Mean bumblebee residences in the fields studied varied between 490 and 720 flowers. In the absence of a direct measurement of element (3), we calculated the maximum level of bumblebee‐mediated gene flow by assuming that all bees arrived at the sink saturated with pollen from extrinsic sources. In this case, the model predicts that bumblebee‐mediated gene flow accounted for between 0.1% and 0.5% of the progeny in the agricultural fields studied. A likelihood analysis of our observations is unable to reveal convincingly the proportion of bees arriving at the sink via a source population, but the literature suggests that bumblebees have high site fidelity, which implies that bee‐mediated gene flow may be substantially less than our estimated maximum. We consider the role of various factors, including wind pollination, in accounting for the differences between the model's predictions and the generally higher levels of gene flow observed in previous studies of oilseed rape.