bluuebunny/crossref_metadata_2025 huggingface dataset:
Science and technology capacity building and partnership in African agriculture: perspectives on Mali and Egypt
Authors: Ayele Seife , Wield David
Published: June 2005

Science and technology (S&T) have long been seen as key for development. This paper considers the issue of capacity building in the light of recent reconceptualization of the role of science and technology in development. Reconceptualization suggests that science and technology are better seen as key elements of innovation systems, which are themselves the means of gaining value from knowledge creation; and, that innovation, knowledge and development are tightly knit elements of a system of organisations and institutions that must function coherently for improved knowledge and innovation systems to emerge. Developing such systems requires linkages of many types. The paper describes and discusses the conceptual basis for capacity building interventions, using partnership‐based capacity building initiatives in new agricultural technologies from Mali and Egypt. The empirical analysis from both countries shows evidence of research capacity building in the form of recruitment, training of scientific staff and provision of research infrastructure. Unsurprisingly, given the S&T knowledge base, the Malian case illustrates the difficulty of moving beyond basic forms of research capacity building. In Egypt, with significant S&T capacity, there is evidence of organizational and institutional innovation towards broader knowledge, and innovation system development in agri‐biotechnology. The role of partnerships, and government as ‘systems‐builder’, are shown to be important. Lessons are drawn from these (and other) cases about the relationship between partnerships, S&T and innovation capacity building. Copyright © 2005 John Wiley & Sons, Ltd.
Context‐bound knowledge production, capacity building and new product networks
Authors: Smith James
Published: June 2005

This paper seeks to analyse a partnership‐led veterinary vaccine initiative, the East Coast Fever Project, as a potentially new model of institutionally disembedded research and development partnership that functions in a developing country context. The paper is theoretically informed by work on knowledge and power within development studies, and partnerships and information within studies of innovation systems. This dual approach raises interesting questions and insights for understanding how research institutions function in a developing country context. The case study itself provides an example of a more ‘complete’ approach to innovation, understanding the need to both identify needs and priorities, and to engage with ways to market the vaccine. This new product network unconsciously speaks to many of the issues raised by studies of development and innovation and as a result is quite successful in navigating through complex institutional relationships and in building research capacity. Copyright © 2005 John Wiley & Sons, Ltd.
Formal and informal governance of agricultural biotechnology in Kenya: participation and accountability in controversy surrounding the draft biosafety bill
Authors: Harsh Matthew
Published: June 2005

Formal governance of agricultural biotechnology in Kenya—i.e. national institutional and policy developments—has been loosely co‐ordinated and largely reactive, both in terms of bio‐safety and in terms of setting national priorities. At the same time, modern biotechnology developments have been occurring for over a decade, mainly driven by public‐private partnerships. Governance of biotechnology has thus been largely informal with strategic decisions being made mainly outside state mechanisms. The distinction between formal and informal governance sheds light on the current draft biosafety bill of Kenya and how it is pivotal for tipping biotechnology developments more towards increased accountability and open participation of farmers and publics. The government of Kenya, non‐governmental actors and donors must all make actions to shape a more productive interaction between formal and informal governance to avoid immediate and long‐term repercussions. Copyright © 2005 John Wiley & Sons, Ltd.
Science and governance of modern biotechnology in Sub‐Saharan Africa—the case of Uganda
Authors: Wafula David , Clark Norman
Published: June 2005

Science policy, particularly as it applies to biotechnology and biosafety, has no single ‘correct’ approach to follow. An objective approach to biotechnology policy however requires three essential components: scientific advice, the engagement of a range of stakeholders in policy dialogue, and effective governance at a systemic level, in an ‘innovation systems’ sense, forming closer interaction between organizations and personnel to ensure that knowledge flows are maintained at all times. The article discusses the governance of modern biotechnology in Uganda. It shows that some progress is being made on interactivity among scientific organizations—many of whom are on the threshold of a capacity to become involved in gene transfer with potential application to the national needs. Interactivity, however, does not appear to be strong amongst governance bodies. Similarly the development of national policy, while strong in inspirational terms, seems in practice to be rather ad hoc and piecemeal, with uncertainty about who makes decisions and how these are to be implemented, monitored and evaluated. So, from an ‘innovation systems’ standpoint the governance of modern biotechnology in Uganda still has some way to go. Copyright © 2005 John Wiley & Sons, Ltd.
Role of development in the evolution of the scapula of the giant sthenurine kangaroos (Macropodidae: Sthenurinae)
Authors: Sears Karen E.
Published: June 2005

Extinct giant sthenurine kangaroos possessed scapulae morphologically distinct from those of all other extant and extinct adult macropodids, but qualitatively resembling those of newborn macropodids. The similarity between adult sthenurine and neonatal macropodid scapulae suggests that a developmental process, such as heterochrony, might have been behind the evolution of the unique sthenurine scapular morphology. By incorporating adult and ontogenetic data, this study examines the evolution and development of the sthenurine scapula. This study quantitatively upholds the previous qualitative morphological observations of macropodid scapulae and finds that ontogenetic and evolutionary morphological changes are correlated in macropodids. The similarity of scapula morphology in sthenurines and newborn macropodids, the correlation between ontogenetic and evolutionary morphological change, and information from other sources (i.e., sthenurine evolutionary history) suggests that pedomorphic shifts in morphology, most likely due to neotenic processes, occurred within the development of the scapula of giant sthenurines. J. Morphol. © 2005 Wiley‐Liss, Inc.
Hepatitis C virus infection in 2,744 hemodialysis patients followed regularly at nine centers in Hiroshima during November 1999 through February 2003
Authors: Kumagai Junko , Komiya Yutaka , Tanaka Junko , Katayama Keiko , Tatsukawa Yorimitsu , Yorioka Noriaki , Miyakawa Yuzo , Yoshizawa Hiroshi
Published: June 2005

Patients on maintenance hemodialysis (HD) are at increased risk of infection with hepatitis C virus (HCV). A prospective follow‐up study on HCV infection from November 1999 to February 2003 was conducted in nine hemodialysis (HD) units in Hiroshima. A total of 2,744 HD patients were surveyed regularly for HCV RNA in serum. The prevalence of HCV RNA decreased from 15.7% (262/1,664) on the first survey to 12.9% (242/1,882) in the last one (P < 0.05). This decrease may be attributed to the inclusion of patients with a lower prevalence of HCV RNA compared to patients leaving dialysis centers (111/1,080 [10.3%] vs. 132/862 [15.3%], P < 0.01). During the 40 months of this study, 16 de novo HCV infections were documented in the nine HD units corresponding to an incidence of 0.33% per year. These cases included eight new HCV infections, three re‐infections, and five infections that presumably occured in the window period when tested during the first survey. Our study shows that the annual incidence of de novo HCV infection during HD was 0.33%, and emphasizes the need for frequent serum HCV RNA testing and for stringent disinfection procedures in order to prevent the transmission of HCV in these settings. J. Med. Virol. 76:498–502, 2005. © 2005 Wiley‐Liss, Inc.
Detection and genotyping of GBV‐C virus in the United Arab Emirates
Authors: Abu Odeh Raed O. , Al‐Moslih Moslih I. , Al‐Jokhdar Mohammed Wafi , Ezzeddine Sinda A.
Published: June 2005

GB virus‐C/Hepatitis G virus (GBV‐C/HGV), collectively known as GBV‐C, is spread widely and has been reported to be associated with non A‐E hepatitis. The aim of the current project was to determine the rate of infection and genotypic characteristics of GBV‐C in the United Arab Emirates (UAE). A total of 379 plasma/serum samples representing different populations in the UAE and comprising healthy as well as patients positive for HBV and HCV were screened using RT‐PCR/nested PCR of the 5′‐untranslated region (UTR). National subjects (n = 168) and non‐nationals residing in the UAE (n = 211) were tested. The results obtained showed that the rate of GBV‐C infection in healthy nationals, and those positive for HCV or HBV were 11.1%, 14.3%, and 5.7%, respectively, compared to 8.3%, 33.3%, and 8.6%, respectively, in non‐nationals. No statistically significant correlation between infection with GBV‐C and HCV or HBV (P > 0.05) was found. Sequence analysis of the 5′‐UTR using 37 and 46 clones from 8 and 6 healthy nationals and non‐nationals, respectively, revealed the prevalence of the European/North American genotype 2 when compared to the five reference genotypes in GenBank. J. Med. Virol. 76:534–540, 2005. © 2005 Wiley‐Liss, Inc.
Unexpected occasional persistence of high levels of HHV‐6 DNA in sera: Detection of variants A and B
Authors: Ward Katherine N. , Thiruchelvam Anton D. , Couto‐Parada Xosé
Published: June 2005

Previously it was thought that in the immunocompetent human herpesvirus‐6 [HHV‐6] DNA was present transiently in serum during early primary infection but not thereafter. In this study, HHV‐6 serum IgG avidity was detected by immunofluorescence and HHV‐6 variants A/B [HHV‐6A/B] serum DNA by semi‐quantitative PCR [titre—log10 copies/ml] in: (a) young children <3 years old from an encephalitis Survey, and a control Anonymised Serum Bank and (b) children/adults referred for diagnosis. The results showed that 11 out of 15 children [all <2 years] with primary infection proven by seroconversion had transient low levels of serum HHV‐6B DNA [mean titre 2.6]. However, 3.3% (6/184) of Survey Children had significantly higher levels [mean titre 5.3; 2 HHV‐6A; 4 HHV‐6B; P < 0.001]. Similarly high level serum DNA [mean titre 4.0; 4 HHV‐6A; 6 HHV‐6B] was found in 1.5% (10/653) of the Serum Bank Children. Moreover, seven young children <3 years old [four Survey Children and three referred for diagnosis] had high titre serum HHV‐6 DNA [mean 4.8] persisting i.e., in all available samples [median 186 days]. Three older children >3 years old and 4 adults [3 of whom were the mothers of 3 of the young children with persisting HHV‐6] also had persisting high titre viral DNA [mean 4.2; median 108 days]. Thus in contrast to acute primary infection, where only HHV‐6B DNA is found transiently, both HHV‐6A and B DNA persist in serum at high titre in occasional individuals of all ages. The significance of this newly described phenomenon in relation to diagnosis, clinical consequences and congenital infection are discussed. J. Med. Virol. 76:563–570, 2005. © 2005 Wiley‐Liss, Inc.
Serum IgA levels induced by rotavirus natural infection, but not following immunization with the RRV‐TV vaccine (Rotashield™), correlate with protection
Authors: González Rosabel , Franco Manuel , Sarmiento Luis , Romero Milagros , Schael Irene Pérez
Published: June 2005

To directly compare serum rotavirus specific IgA as a marker of protection in children vaccinated with the RRV‐TV (Rotashield™) vaccine and in naturally infected children, we studied pre‐existing rotavirus IgA antibodies by ELISA assays in these groups of children within the first 5 days after the onset of a diarrhea episode, due or not to rotavirus. In immunized children, rotavirus IgA titers were similar between infected and non‐RV infected children. In non‐immunized children, the proportion with rotavirus IgA titers was significantly greater in non‐RV infected children (58%) than in infected children (31%). Additionally, a titer ≥1:800 was associated with 68% protection. Thus, in this study serum rotavirus IgA showed a good correlation with protection in children pre‐exposed to natural infection but not in those immunized with the RRV‐TV vaccine. J. Med. Virol. 76:608–612, 2005. © 2005 Wiley‐Liss, Inc.
The bistable TPID/CHCl3 photoreaction: Numerical simulation and experimental results
Authors: Borderie B. , Lavabre D. , Levy G. , Micheau J. C. , Laplante J. P.
Published: June 2005

Investigation of the photochromic system TPID/CHCl3 (TPID = triphenylimidazolyl dimer) in a CSTR provided the first example of isothermal photochemical bistability. The reaction mechanism was established and the relevant kinetic and spectroscopic parameters were estimated experimentally. In order to predict the quantitative dynamic behavior of the TPID/CHCl3 system these parameters were refined numerically using batch reactor data.

The adjusted model simulates very accurately bistability either as a function of residence time τ, or as a function of incident photon flux I0.
An experimental and modeling study of ethanol oxidation kinetics in an atmospheric pressure flow reactor
Authors: Norton T. S. , Dryer F. L.
Published: June 2005

Experimental profiles of stable species concentrations and temperature are reported for the flow reactor oxidation of ethanol at atmospheric pressure, initial temperatures near 1100 K and equivalence ratios of 0.61–1.24. Acetaldehyde, ethene, and methane appear in roughly equal concentrations as major intermediate species under these conditions. A detailed chemical mechanism is validated by comparison with the experimental species profiles. The importance of including all three isomeric forms of the C2H5O radical in such a mechanism is demonstrated. The primary source of ethene in ethanol oxidation is verified to be the decomposition of the C2H4OH radical. The agreement between the model and experiment at 1100 K is optimized when the branching ratio of the reactions of C2H5OH with OH and H is defined by (30% C2H4OH + 50% CH3CHOH + 20% CH3CH2O) + XH. As in methanol oxidation, HO2 chemistry is very important, while the H + O2 chain branching reaction plays only a minor role until late in fuel decay, even at temperatures above 1100 K.
Gas‐phase reactions of 1,4‐benzodioxan, 2,3‐dihydrobenzofuran, and 2,3‐benzofuran with OH radicals and O3
Authors: Atkinson Roger , Arey Janet , Tuazon Ernesto C. , Aschmann Sara M.
Published: June 2005

The kinetics of the gas‐phase reactions of 1,4‐benzodioxan, 2,3‐dihydrobenzofuran, and 2,3‐benzofuran with OH radicals and O3 have been studied at 298 ± 2 K and atmospheric pressure of air and the products have also been investigated. 1,4‐Benzodioxan and 2,3‐dihydrobenzofuran were chosen as volatile model compounds for dibenzo‐p‐dioxin and dibenzofuran, respectively. The rate constants, or upper limits thereof, for the O3 reactions were (in cm3 molecule−1 s−1 units): 1,4‐benzodioxan, <1.2 × 10−20; 2,3‐dihydrobenzofuran, <1 × 10−19; and 2,3‐benzofuran, (1.83 ± 0.21) × 10−18. Using a relative rate method, the rate constants for the OH radical reactions (in cm3 molecule−1 s−1 units) were: 1,4‐dibenzodioxan, (2.52 ± 0.38) × 10−11; 2,3‐dihydrobenzofuran, (3.66 ± 0.56) × 10−11; and 2,3‐benzofuran, (3.73 ± 0.74) × 10−11. Salicylaldehyde was observed as a product of the OH radical‐initiated and O3 reactions of 2,3‐benzofuran, with measured formation yields of 0.26 ± 0.05 and 0.13 ± 0.07, respectively.
Role of ionic strength in the kinetics of formation of the monochelate of nickel(II) with heptane‐3,5‐dione
Authors: Moyá María Luisa , Rodriguez Amalia , Sánchez Francisco , Blanco Carlos , Hynes Michael J.
Published: June 2005

The kinetics and mechanism of the reaction of Ni(II) with heptane‐,5‐dione (Hhptd) have been investigated in concentrated sodium perchlorate aqueous solutions at 298 K. The kinetic data in the different media are consistent with a mechanism in which Ni(II) reacts with the enol form of the ligand. The observed positive salt effect on the rate of the reaction of formation of the complex Nihptd+ is rationalized taking into account the increase of the rate of water exchange from the first solvation sphere of the metal ion to the bulk solvent when increasing salt concentration.
FTIR spectroscopic study of the Cl‐ and Br‐atom initiated oxidation of ethene
Authors: Yarwood G. , Peng N. , Niki H.
Published: June 2005

The reaction mechanism of the halogen (Cl and Br)‐atom initiated oxidation of C2H4 was studied using the long path FTIR spectroscopic method in 700 torr of air at 296 ± 2 K. Among the major halogen‐containing products were XCH2CHO, XCH2CH2OH, and XCH2CH2OOH (X = Cl or Br) which were shown to be formed via the self‐reaction of the XCH2CH2OO radicals, i.e., 2XCH2CH2OO → 2XCH2CH2O + O2; (a) 2XCH2CH2OO → XCH2CHO + XCH2CH2OH + O2 and (b) followed by XCH2CH2O + O2 → XCH2CHO + HO2 and XCH2CH2OO + HO2 → XCH2CH2OOH + O2. From the observed yields of XCH2CHO and XCH2CH2OH the branching ratios for reactions (a) and (b) were determined to be ka/kb = 1.35 ± 0.07(2σ) for both X = Cl and Br. In addition, the O2‐dependence of the rate constant for the Br + C2H4 reaction was determined by the relative rate technique as a function of O2 partial pressure from 140 to 700 torr at 700 torr total pressure of N2/O2 diluent. Rate constants for the reactions of Cl‐atoms with Cl‐CH2CHO and Br‐atoms with Br‐CH2CHO were also determined to be [4.3 ± 0.2(2sigma;)] × 10−11 and less than or equal to [1.83 ± 0.11(2σ)] × 10−13 cm3 molecule−1 s−1, respectively.
Kinetic study of n‐heptane oxidation
Authors: Chakir A. , Bellimam M. , Boettner J. C. , Cathonnet M.
Published: June 2005

The oxidation of n‐heptane has been studied in a jet‐stirred flow reactor in the temperature range 950–1200 K at atmospheric pressure for a wide range of fuel‐oxygen equivalence ratios (0.2 to 2.0). A chemical kinetic reaction mechanism developed from previous studies on smaller hydrocarbons and extended to C6 and C7 species was used to reproduce the experimental data. Good agreement between computed and measured concentrations of major chemical species was obtained for the entire range of experimental conditions. Sensitivity analyses were carried out to identify the reactions having the greatest influence on the modeling results. The major reaction paths for n‐heptane consumption and for the formation of the main products have been identified.

In addition n‐heptane ignition delays behind a reflected shock wave measured by other investigators were used to validate the present reaction mechanism at higher temperature and pressure.
Influence of anodic oxidation at low potential on the Corrosion resistance of hafnided zirconium in concentrated sulphuric media
Authors: Chatainier G. , Petit J. A. , Dabosi F.
Published: June 2005

In the context of increasing applications of zirconium in the chemical processing industry the influence of anodic oxidation at low potentials on the corrosion resistance of zirconium has been studied. Experiments were performed in concentrated sulphuric acid media, using electrochemical methods. A transition range of potentials between −65 and −50 mV/SCE has been observed. On each side of this transition range hafnided zirconium covered with passive film exhibits different corrosion resistance. Alteration of the passive film, which can be assumed from nuclear microanalysis experiments, has been hypothesized to take account for the modification of the electrochemical behaviour.
Schadensfälle an chirurgischen Implantaten und deren Ursachen
Authors: Zitter H. , Schaschl‐Outschar D.
Published: June 2005

Seit dem erstmaligen Einsatz von Chrom‐Nickel‐Molybdän‐Stählen für Implantate in den 30er Jahren, hat die Entwicklung der chemisch beständigen Stähle große Fortschritte gemacht, die in den Werkstoffnormen für Implantate bis heute kaum einen Niederschlag gefunden haben.

Eine statistische Auswertung von Schadensfällen läßt in Übereinstimmung mit der Lage der charakteristischen Potentiale erkennen, daß Lochfraß, Spaltkorrosion und die dadurch verursachten Korrosionsdauerbrüche durch höhere Chrom‐ und Molybdängehalte leicht vermieden werden können. Stähle, die diesen Anforderungen gerecht werden, sind in allen Normen enthalten und würden allein vom wirtschaftlichen Standpunkt ihren Einsatz rechtfertigen.
Intergranular corrosion of alloy 800 by the electrochemical potentiokinetic reactivation method
Authors: Borello A. , La Barbera A. , Mignone A. , Vittori M.
Published: June 2005

The “Electrochemical Potentiokinetic Reactivation” method has been employed to quantify the degree of intergranular corrosion of Alloy 800, with different Ti + Al content, aged in the range 500–650°C for times up to 5000 hours. The results were compared with the classical Rollason's curves obtained by means of the Strauss' test and a satisfactory agreement was found.

An explanation of the slight differences between both methods has been proposed on the basis of the passivity film morphology.
Veränderungen Feuerfester Pulver beim Plasmaspritzen
Authors: Pilous V.
Published: June 2005

Es werden Ergebnisse des Durchgangs von Pulvern auf der Basis von NiCrBSi, A12O3‐TiO2 und Mo durch den Plasmabogen bei Temperaturen von 16000 K und 20000 K angeführt. Weiter wird der Gefügeaufbau von Ni3B und Al2O3 beim Durchgang verfolgt. Plasmabogentemperaturen zum Spritzen von Pulvern der erwähnten Basen werden empfohlen.
The effect of thermo‐mechanical treatment on The pitting corrosion of reinforcing carbon steel bars
Authors: Groza Joanna R. , Eslamloo‐Grami M. , Bandy R.
Published: June 2005

Steel reinforcing rods with varying amounts of cold work and carbon concentrations (0.06 to 0.45% C) exposed in soil embankments has shown various degrees of pitting corrosion. To understand this pitting process, laboratory investigations on residual stresses, microstructures and potentiodynamic cyclic polarization were undertaken. Analysis of residual stresses in the steels indicated low value of compressive stresses in hot rolled steels and high value of tensile stresses in the cold worked counterparts. Hot rolled steels displayed a slightly better pitting corrosion resistance than cold worked samples which is consistent with the above internal stress pattern. No definite correlation was obtained between the percentage of carbon in the steels and pitting susceptibility. An attempt has been made to define the role of the complex steel‐soil system for pitting corrosion behavior.
Beeinträchtigung der Lochkorrosionsbeständigkeit von CrNi‐Stählen durch dünne Oxidschichten
Authors: Diab A. S. M. , Schwenk W.
Published: June 2005

Proben aus Werkstoff‐Nr. 1.4301 und 1.4571 wurden mittels potentiostatischer Halteversuche auf chlorid‐induzierte Lochkorrosion untersucht. Parameter waren der Oberflächenzustand mit dünnen Oxidschichten (Anlauffarben bis blau), Zusatz von Inhibitoren (Sulfate, Nitrate), Temperatur. Es wurden zwei Lochfraßpotentiale ermittelt, die über stabile Passivität, latente und stabile Lochkorrosion informieren.

Die Ergebnisse zeigen, daß der Einfluß der Temperatur und des Mo‐Gehaltes nicht sehr groß ist. Einen starken Einfluß können die Inhibitorzusätze haben. Gebeizte Proben sind wesentlich beständiger als solche mit strohgelber Anlauffarbe, während die Lochfraßbeständigkeit zwischen Proben mit gelber und blauer Anlauffarbe nicht sehr unterschiedlich ist. Im Trend werden aber die Lochfraßpotentialbereiche mit zunehmender Oxidschichtdicke (gelb bis blau) erweitert.
Saccharide und deren Derivate als Korrosionsinhibitoren für Aluminiumpigmente in wäßrigen Medien
Authors: Müller Bodo , Kurfeß Martin
Published: June 2005

Aluminiumpigmente (Al‐Gehalt > 99,5%) unterliegen in wäßrigen, leicht alkalischen Metalliclacken der Korrosion, deren zeitlicher Verlauf sich durch volumetrische Bestimmung des entstehenden Wasserstoffs leicht verfolgen läßt. Als einfache Modellsysteme zur Prüfung von Mono‐, Di‐ und Polysacchariden, sowie Derivaten davon, als Korrosionsinhibitoren wurden zwei Wasser/Butylglykol‐Gemische gewählt, deren pH‐Wert zur Beschleunigung der Korrosionsreaktion auf 10 eingestellt wurde. Darüber hinaus wurde versucht, durch Vergleich mit geeigneten Modellsubstanzen Struktur‐Wirkungs‐Beziehungen aufzustellen. Zwei Substanzklassen erwiesen sich als wirksam:

Reduzierend wirkende Mono‐ und Disaccharide inhibieren die Korrosion wahrscheinlich über das im Gleichgewicht vorliegende Endiolstukturelement.

Die untersuchten Hydroxycarbonsäuren bilden vermutlich Chelatkomplexe, die dann korrosionsinhibierend wirken.

Als wirksamster aller hier untersuchten Inhibitoren zeigte sich das stark reduzierend wirkende Endiol Ascorbinsäure.
Einfluß von Passivierungs‐ und Kohlenstoffschichten auf austenitischen CrNiMo‐Stählen auf die Beständigkeit gegen Lochfraß und Spannungsrißkorrosion
Authors: Marciniak J. , Boba J. , Paszenda Z. , Mitura S.
Published: June 2005

Der Einfluß von Passivierungsschichten und Schichtkombinationen (bestehend aus einer Passivierungs‐ und einer Kohlenstoffschicht) auf die Beständigkeit von austenitischen CrNiMo‐Stählen gegen Lochfraß und Spannungsrißkorrosion wurde in physiologischer Tyrode‐Lösung im pH‐Bereich 6,9 bis 7,4 bei 37 ± 1°C untersucht. Die Passivierungsschicht wurde ‐ nach elektrolytischem Polieren in H3PO4+ H2SO4+ C6H5NHCOCH3+ Oxalsäure + Korrosionsinhibitor CS ‐ durch Behandeln mit 40% iger Salpetersäure, die Kohlenstoffschicht durch CVD erzeugt. Die Verunreinigung des Stahls durch nichtmetallische Einschlüsse und der Phasenbestand wurden untersucht und die chemische Zusammensetzung der Passivierungsschicht durch quantitative Analyse ermittelt. Die Widerstandsfähigkeit des Stahls ‐ mit und ohne Passivierungsschicht ‐ gegen Lochfraß wurde potentiodynamisch in Chloridlösung nach Tyrode bei 37 ± 1°C untersucht. Die Beständigkeit gegen Spannungsrißkorrosion wurde in Tyrode‐Lösung bei 37 ± 1°C, in neutralem Glycerin sowie 44% iger MgCl2‐Lösung bei 154°C ± 1°C untersucht und unter Verwendung von Kσund Kτbeurteilt. Die Korrosionsschäden wurden licht‐ und rasterelektronenmikroskopisch untersucht.

Die Untersuchungen haben gezeigt, daß die verwendeten Oberflächenschichten die Beständigkeit der Stähle gegen Lochfraß und Spannungsrißkorrosion in den verwendeten Medien wirksam verbessern und damit die Verwendung dieser Materialien für chirurgische Implantate ermöglichen.
Propene‐Ethene Copolymers Synthesised with Cs‐Symmetric Metallocenes and Different Cocatalysts
Authors: Seraidaris Tanja , Kaminsky Walter , Seppälä Jukka V. , Löfgren Barbro
Published: June 2005

Summary: Propene‐ethene copolymers with low to moderate amounts of ethene were synthesised with two Cs‐symmetric metallocene complexes, [(p‐CH3OPh)2C(2,7‐di‐tBuFlu)(Cp)]ZrCl2 (I) and [(p‐CH3OPh)2C(2,7‐di‐tBuFlu)(Cp)]HfCl2 (Ia). Methylalumoxane (MAO), N,N‐dimethylanilinium tetra(pentafluorophenyl)borate {[Me2HNPh][B(C6F5)4]}, trityl tetra(pentafluorophenyl)borate {[Ph3C][B(C6F5)4]} and tris(pentafluorophenyl)borane [B(C6F5)3] were used as cocatalysts in the polymerisations. The differences in polymerisation activity, ethene incorporation rate and molecular weight as well as the microstructure and the thermal behaviour of the homo‐ and copolymers were studied.

The different cocatalysts have a strong influence on the polymerisation activity and the syndiotacticity of the polymers, but only a minor influence on the ethene incorporation rate and the molecular weight. At 30 °C, the incorporation rate of ethene is ca. 25 times faster for complex I and ca. 16 times faster for complex Ia than the incorporation rate of propene. The thermal behaviour of the homo‐ and copolymers is dependent of the polymerisation temperature and the cocatalyst. I/MAO produces homo‐ and copolymers at 30 °C with more regular microstructure than I/[Me2HNPh][B(C6F5)4], I/[Ph3C][B(C6F5)4] and I/B(C6F5)3 leading to homo‐ and copolymers with higher melting and crystallisation temperatures. On the contrary, at 0 °C I/[Me2HNPh][B(C6F5)4] and I/[Ph3C][B(C6F5)4] produce copolymers with higher propene sequence syndiotacticity and higher melting and crystallisation temperatures than I/MAO. The influence of the cocatalyst on the catalyst coordination environment is temperature‐dependent and thereby the structure of the forming homo‐ or copolymers varies.

Effect of different cocatalysts and the amount of ethene in the feed on the polymerisation activity of complex I.

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Effect of different cocatalysts and the amount of ethene in the feed on the polymerisation activity of complex I.
Polyester Dendrimers Carrying NLO Chromophores: Synthesis and Optical Characterization
Authors: Do Jung Yun , Ju Jung Jin
Published: June 2005

Summary: Four dendritic polyesters containing non‐linear optical chromophores on the periphery were synthesized and their material properties were compared for electro‐optic device applications. Thermal and optical parameters of the dendrimer materials were measured along with structural analysis. A high chromophore concentration in the dendritic polyesters produced enhancement of the optical non‐linearity. The second generation dendrimer (G1‐DAIDC) exhibited an electro‐optic coefficient of 43.4 pm · V−1 at 1.55 µm optical communication wavelength. Aromatic ester backbones elevate the glass transition temperature of the chromophore alignment, representing good thermal stability of the optical films.

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New Silicon‐Containing Polyquinolines: Synthesis, Characterization, and Electroluminescence
Authors: Tonzola Christopher J. , Alam Maksudul M. , Jenekhe Samson A.
Published: June 2005

Summary: This study reports the synthesis, characterization, and electroluminescent device application of three new silicon‐containing polyquinolines: poly(2,2′‐(bis(p‐phenyl)diphenylsilane)‐6,6′‐bis(4‐phenyl quinoline)), poly(2,2′‐(bis(p‐phenyl)octylmethylsilane)‐6,6′‐bis(4‐phenyl quinoline)), and poly(2,2′‐(bis(p‐phenyl)diphenylsilane)‐6,6′‐bis(4‐hexylquinoline)). The polymers with alkyl side chains were soluble in organic solvents. The new polymers showed robust thermal properties with glass transitions of 161–339 °C. Cyclic voltammetry of the polymers revealed quasi‐reversible reductions with onsets of −1.55 to −1.71 V (vs SCE) and corresponding electron affinities of 2.69–2.85 eV. Organic light‐emitting devices using new polyquinolines as emissive materials showed blue (CIE coordinates = 0.21, 0.20) or blue‐green (0.23, 0.36) electroluminescence with a moderate brightness (≈140 cd · m−2) and efficiency (0.04%). The results demonstrate that silicon‐containing polyquinolines are promising n‐type wide band‐gap semiconductors for organic electronics.

Structures of new Si‐containing polyquinolines.

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Structures of new Si‐containing polyquinolines.
Site Specific Proton and Deuteron NMR Relaxation Dispersion in Selectively Deuterated Polyisoprene Melts
Authors: Kariyo Sobiroh , Stapf Siegfried , Blümich Bernhard
Published: June 2005

Summary: The frequency dependence of proton and deuteron NMR relaxation times was determined in selectively deuterated and undeuterated polyisoprene melts and compared to polybutadiene melts. Master curves were generated by the Williams‐Landel‐Ferry (WLF) formalism which resulted in very similar dispersions for all samples with a high and a low frequency branch following characteristic power laws. The results show a consistently weaker frequency dependence than any reported so far for other polymer melts. The reason for this finding is identified in the distribution of intramolecular motion modes, while intermolecular contributions are ruled out.

Master curves for 1H relaxation dispersions obtained from measurements between 223 K and 348 K shifted relative to a reference temperature of 296 K.

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Master curves for 1H relaxation dispersions obtained from measurements between 223 K and 348 K shifted relative to a reference temperature of 296 K.
Restricted Molecular Dynamics of Polymer Chains by Means of NMR Field Cycling Relaxometry
Authors: Kariyo Sobiroh , Stapf Siegfried
Published: June 2005

Summary: The molecular dynamics of polymer melts with molecular weights above their critical values have been described by a power law dependence of the spin‐lattice relaxation time on the Larmor frequency. Three different regimes of power laws describing the relaxation dispersion of polymers for the chain mode dynamics are distinguishable and have been observed experimentally for several types of polymers. In this study, the influence of chemical and physical constraints on the relaxation dispersion of polymers was investigated. This included the introduction of chemical cross‐links and filler particles to produce elastomers, for which further constraints were imposed by mechanical deformation. As an alternative means of affecting molecular mobility, investigations were also carried out for poly(styrene‐block‐butadiene) diblock and poly(styrene‐block‐butadiene‐block‐styrene) triblock copolymers. Reducing the molecular degree of freedom of the chain, i.e., by introducing cross‐links between different segments, was shown to affect the time scale of motion but left the spectrum of the reorientational dynamics virtually unchanged. Only a small effect was found on the addition of filler particles into the elastomer network. On the other hand, applying macroscopic deformation to natural rubber and butadiene rubber samples is shown to alter also the spectrum of reorientations. Generating chemical fixations to immobile microdomains by copolymerizing a soft butadiene phase with a hard polystyrene phase to produce a biphasic lamellar structure is demonstrated to have a comparable effect. The change in slow molecular motion in the kHz to MHz range is discussed using the corresponding frequency dependence of the NMR spin‐lattice relaxation time, and a common description combining measurements at different temperatures is presented.

Master curves generated from relaxation dispersions at different temperatures for a BR1/1 sample filled with 30 phr of carbon black under deformation with λ ≈ 3.5 (compared to an unstretched sample).

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Master curves generated from relaxation dispersions at different temperatures for a BR1/1 sample filled with 30 phr of carbon black under deformation with λ ≈ 3.5 (compared to an unstretched sample).
Design and Properties of Degradable Networks Based on Free Radical Copolymerization of Poly(1,3‐dioxolane) Macromonomers with Hydrophobic or Hydrophilic Comonomers in Water
Authors: Sahli Nabahat , Belbachir Mohamed , Lutz Pierre J.
Published: June 2005

Summary: Potentially degradable amphiphilic or hydrophilic copolymeric networks were synthesized directly in water by free radical copolymerization of α, ω‐poly(1,3‐dioxolane) (PDXL) macromonomers with vinyl monomers such as methyl methacrylate, butyl methacrylate, styrene or 2‐hydroxyethyl methacrylate. Since PDXL macromonomers behave typically as amphiphiles, the rates of copolymerizations with hydrophobic comonomers are much higher than those of similar reactions carried out in organic solvents. Therefore crosslinking in water takes place rapidly. Once swollen to equilibrium in appropriate solvents, the physicochemical properties of the amphiphilic (or hydrophilic) copolymeric PDXL networks were investigated. The volume degree of equilibrium swelling and uniaxial compression modulus strongly depended upon the macromonomer molar mass (and concentration), and also the hydrophobic/hydrophilic balance. Their solid state properties were examined by DSC and compared to those of homopolymeric PDXL networks.

Amphiphilic PDXL conetworks synthesized directly in water by free radical copolymerization of bifunctional PDXL macromonomers with hydrophobic comonomers such as styrene or butyl methacrylate.

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Amphiphilic PDXL conetworks synthesized directly in water by free radical copolymerization of bifunctional PDXL macromonomers with hydrophobic comonomers such as styrene or butyl methacrylate.
Scaling Behaviour of PAMAM Dendrimers Determined by Diffusion NMR
Authors: Fritzinger Bernd , Scheler Ulrich
Published: June 2005

Summary: The hydrodynamic radius of PAMAM dendrimers as a function of molar mass is investigated by diffusion NMR. As a characteristic length, the hydrodynamic radius is calculated by Stokes‐Einstein equation. Poly(amidoamine) (PAMAM) dendrimers of generations 0 to 7 of two different terminal groups (NH2, COONa) have been investigated. This dependence of the hydrodynamic radius from molar mass is compared with a scaling model and statistical model. A scaling exponent of 3.7 has been found in both cases. The scaling exponent found exceeds the dimension of the embedding space, thus the possible growth of dendrimers of this structure is limited.

Hydrodynamic radius of PAMAM‐NH2 □, PAMAM‐COONa ○ as a function of molar mass.

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Hydrodynamic radius of PAMAM‐NH2 □, PAMAM‐COONa ○ as a function of molar mass.
Electroluminescent and Photovoltaic Properties of the Crosslinkable Poly(phenylene vinylene) Derivative with Side Chains Containing Vinyl Groups
Authors: Yang Chunhe , Hou Jianhui , Zhang Bin , Zhang Shaoqing , He Chang , Fang Huan , Ding Yuqin , Ye Jianping , Li Yongfang
Published: June 2005

Summary: The photoluminescence (PL), electroluminescence (EL), and photovoltaic properties of a poly(phenylene vinylene) derivative with its side chains containing vinyl groups, poly[(2,5‐bis‐allyloxyphenylene vinylene)‐co‐(2‐methoxy‐5‐(2′‐ethylhexyloxy)phenylene vinylene)] (A‐PPV) are reported. A‐PPV with the active vinyl units in the end of its side chains can be crosslinked either by UV light irradiation or heating. The crosslinking does not change the color of light emitted from the A‐PPV polymer light‐emitting diode (PLED). FTIR confirms that the photo/heating‐induced crosslinking does not damage the conjugation of polymer at all. However, the PL and EL efficiency of A‐PPV decreased upon photoirradiation due to the existence of residual radicals in the solid‐state film. The relatively stable radicals function as a trap that quenches the luminescence. The blend of A‐PPV and noncrosslinkable polymer, poly(2‐methyloxy‐5‐ethylhexyloxyl‐1,4‐phenylene vinylene) (MEH‐PPV) was employed in the fabrication of PLEDs, and the PLED shows improved performance with a luminous efficiency of >1 cd · A−1. The blend keeps the advantage of crosslinkability of the polymers and lessens the effects of the photo‐produced radicals. The photovoltaic cells comprised of A‐PPV and C60 were fabricated and the energy conversion efficiency of the devices with and without UV treatment was similar, both around 0.3%. The UV irradiation on the blend film with C60 seems resistant to the residual radicals.

The I‐V, L‐V plot of PLEDs with A‐PPV treated by UV light.

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The I‐V, L‐V plot of PLEDs with A‐PPV treated by UV light.
Synthesis of Oligo(isobutyl vinyl ether) with a Silyl Enol Ether End Group and their Aldol Reactions with Benzaldehyde
Authors: Sarker Prodip K. , Rimmer Stephen
Published: June 2005

Summary: Cationic polymerizations of isobutyl vinyl ether (iBVE) were carried out in the presence of a difunctional silyl enol ether, 3,3‐dimethylpent‐2,4‐(trimethylsilyloxy)‐1,4‐diene. This procedure gave oligomers with silyl enol ether end groups. The silyl enol ether groups reacted in Lewis acid mediated aldol reactions with benzaldehyde to give predominately the β‐hydroxy ketone product at the chain end. Benzaldehyde could be added either prior to initiation (ab initio methodology) or at a time after the propagation of iBVE had completed (sequential methodology). The ab initio methodology was shown to produce similar materials to the sequential method but the latter required higher reaction temperatures.

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New Materials for Rapid Prototyping Applications
Authors: Stampfl Jürgen , Liska Robert
Published: June 2005

Summary: Rapid prototyping (RP) is a widely used manufacturing tool in the product development cycle. This Highlight article gives a brief overview of the currently available RP techniques with special emphasis on three‐dimensional (3D) printing. The advantages and drawbacks of various RP processes regarding material quality, feature resolution, and surface quality are pointed out. New developments in the field of material development allow the use of polymer ionomers for 3D printing. Using polymer ionomers some of the drawbacks of 3D printing can be eliminated. In particular, the mechanical strength can be increased compared to traditional powder systems used for 3D printing. This article describes the chemical background of polymer ionomers and the relevance of these materials for future developments in RP.

Cellular structures made of photopolymerizable polymers.

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Cellular structures made of photopolymerizable polymers.
Direct Melt Extrusion Processing of Nylon 6/Clay Nanocomposites Based on Pristine Montmorillonite
Authors: Li Ying , Guo Zhaoxia , Yu Jian
Published: June 2005

Summary: An original direct melt extrusion processing of nylon 6/clay nanocomposites was reported based on pristine (Na+‐based) montmorillonite as well as a simple approach using a typical two‐screw extruder. By the application of intercalation agents as the thermodynamic assistants, this method is as an appropriate procedure for industrialized manufacture together with much lowered production cost. Interestingly enough, the synergistic effects of montmorillonite with other inorganic particulates was observed for the first time here.

X‐ray diffraction patterns of pristine MMT and nylon 6/MMT composites with grouped intercalation agents.

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X‐ray diffraction patterns of pristine MMT and nylon 6/MMT composites with grouped intercalation agents.
Cover Picture: Macromol. Rapid Commun. 13/2005
Authors: Pucci Andrea , Bertoldo Monica , Bronco Simona
Published: June 2005

Cover: During drawing, the poly(propylene) chains' reorganization is able to destroy the green luminescent BBS excimer‐type arrangement leading to the prevalence of the blue emission of the isolated molecules. Further details can be found in the Communication by A. Pucci,* M. Bertoldo, and S. Bronco on page 1043.
Haftfestigkeit von Metallschichten auf Stählen bei statischer und wechselnder Beanspruchung
Authors: Bertram W. , Schemmer M.
Published: June 2005

Die Ziele der Arbeit bestanden in der Herstellung von metallgespritzten Proben und Bauteilen mit möglichst hoher statischer und dynamischer Beanspruchbarkeit, im Nachweis dieser Eigenschaften durch entsprechende Messungen und in Empfehlungen für den praktischen Einsatz. Zu diesem Zweck wurden zwei Grundwerkstoffe mit fünf Spritzwerkstoffen nach drei Spritzverfahren beschichtet und anschließend untersucht. Aus den Ergebnissen geht hervor, daß kugelgestrahlte und anschließend metallgespritzte Proben unabhängig von Spritzwerkstoff und ‐verfahren Dauerfestigkeiten erreichen, die denen des jeweiligen kugelgestrahlten ungespritzten Grundwerkstoffs nahekommen.
Microstructural aspects of Thermal Stress Resistance of high‐strength engineering ceramics. Part I: Data of thermal stress resistance of high‐strength engineering ceramics
Authors: Ziegler G.
Published: June 2005

Based on the criteria for the improvement of thermal shock resistance mainly two microstructural aspects of thermal stress resistance are discussed: First, the influence of microstructure on thermal shock resistance to fracture initiation, and second, the improvement of thermal shock resistance on the basis of microstructural considerations. In this connection, data of thermal stress resistance (thermal shock and thermal cycling) of various engineering ceramic materials are presented. Using laboratory grades with well‐defined microstructures the interdependence between various microstructural variables and the mechanical and thermal properties, which control the thermal shock resistance, is discussed and the relation to thermal shock resistance is outlined by the example of the two materials, dense and porous reaction‐bonded Si3N4. Moreover, the improvement of thermal shock resistance by microstructural optimization is demonstrated. Some examples of the improvement of thermal stress resistance by developing advanced composite materials are given.

The paper is divided into three parts: Part I: Data of Thermal Stress Resistance of High‐Strength Engineering Ceramics Part II: Influence of Microstructure on Thermal Shock Resistance of High‐Strength Engineering Ceramics Part III: Improvement of Thermal Stress Resistance of High‐Strength Engineering Ceramics.
Einfluß von Eigenspannungen auf Die Werkstoffanstrengung in wälzbeanspruchten Bauteilen
Authors: Broszeit E. , Adelmann J. , Zwirlein O.
Published: June 2005

Die Beanspruchung eines Werkstoffes in Hertz'schen Kontakten läßt sich z. B. mit der Gestaltänderungsenergie‐Hypothese (Huber, von Mises, Hencky) als Vergleichsspannung berechnen. Diese Vergleichsspannung kann dann zu den lokalen Fließeigenschaften des Werkstoffes direkt in Beziehung gesetzt werden. Bei der Berechnung der Werkstoffanstrengung muß jedoch der Einfluß der Reibung und der Eigenspannungen im Werkstoff berücksichtigt werden. Es wird gezeigt, daß es unbedingt erforderlich ist, einen größeren Bereich des Halbraumes unter dem Kontakt zu betrachten, um das Maximum der Werkstoffanstrengung zu erfassen.
Einfluß der Herstellungsbedingungen von Doppel‐V‐Kerben an Prüfkörpern für den Schlagbiegeversuch nach DIN 53 753
Authors: Moslé H. G. , Hinkel P. , Weidner H.
Published: June 2005

Im Zusammenhang mit DIN 53 753 „Schlagbiegeversuch an Probekörpern mit Loch‐ oder Doppel‐V‐Einkerbung”︁ wurden Versuchen an Probekörpern mit unterschiedlichen Kerbradien (0,1; 0,2; 0,5 mm) durchgeführt und an Proben mit unterschiedlicher Herstellung der Kerben (durch Hobeln und durch Einbringen von Kerben in die Spritzgießform). Es wurden vier verschiedene Thermoplaste, zum Teil mit Kurzglasfaser verstärkt, eingesetzt. Es zeigte sich, daß bei der Verwendung von 0,5 mm Kerbradius alle untersuchten Proben brechen, und daß kaum Unterschiede zwischen „gehobelten”︁ und „eingespritzten”︁ Kerben bestechen. Durch die Wahl eines Radius sind Vergleiche zwischen einzelnen Kunststoffen hinsichtlich ihrer Schlagzähigkeit möglich geworden. Mikrotomschnitte, REM‐Aufnahmen der Bruchfläche und Orientierungsmessungen unter dem Polarisierungsmikroskop ergänzen die Untersuchungen.
Beiträge zur Untersuchung der Korrosion An Modellwerkzeugstählen für kunststoffverarbeitende Maschinen
Authors: Braun D. , Brito H.
Published: June 2005

Der Verschleiß an den Modellwerkzeugstählen 9 S 20 K und 165 X CrMoV 12 bei der Thermoplastverarbeitung wurde mit den Schmelzen von glasfaserverstärkten und unverstärkten Styrol‐Acryl‐nitril‐Copolymeren (SAN), Polypropylen, Acrylnitril‐Butadien‐Styrol‐Pfropfpolymeren (ABS) und Polycarbonat untersucht. Die beim Spritzgißen freigesetzten flüchtigen Substanzen wurden isoliert und mit Gaschromatographie (GC), Gaschromatographie‐Massenspektrometrie (GC‐MS) und Kernresonanzspektroskopie (NMR) charkterisiert; es handelt sich vorwiegend um Kohlenwasserstoffe und Monomere der Kunststoffrohstoffe. Aufgrund der nachweislichen Abwesenheit von Wasser kommt eine elektrochemische Korrosion nicht in Betracht, weshalb chemische Reaktionen vorwiegend zwischen Kunststoffschmelze und Stahloberfläche als Korrosionsursache angesehen werden müssen. Mit Hilfe von rasterelektronenmikroskopischen (REM) Untersuchungen wurden Unterschiede zwischen den mit verschiedenen Schmelzen korrodierten Stählen festgestellt. Untersuchungen der Metalloberflächen mit Sekundärionenmassenspektrometrie (SIMS) ergaben kunststoffspezifische Veränderungen. Auf allen korrodierten Stahloberflächen traten im Vergleich zu den unkorrodierten sowohl hohe spektrale Kohlenstoffintensitäten als auch verstärkte Signale von Verbindungen der Stahlbestandteile Chrom, Mangan und Vanadium auf. Die Reaktion dieser Bestandteile mit der Kunststoffschmelze kann als Ursache für Gitteränderungen im Stahl und die damit verbundenen Eigenschaftsänderungen betrachtet werden.