bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(L‐lactide)‐Degrading Activity in Various Actinomycetes
Authors: Jarerat Amnat , Pranamuda Hardaning , Tokiwa Yutaka 
Published: February 2003

AbstractThe poly(L‐lactide) (PLA)‐degrading ability of actinomycetes obtained from culture collections was examined by the formation of clear zones on PLA‐emulsified agar plates. Using 41 genera (105 strains) of actinomycetes with phylogenetic affiliations based on 16S rRNA sequences, PLA degraders were found to be limited to members of the family Pseudonocardiaceae and related genera. They included Amycolatopsis, Saccharothrix, Lentzea, Kibdelosporangium, and Streptoalloteichus. A large number of PLA degraders were widely distributed within the genus Saccharothrix. Most strains forming clear zones on PLA‐emulsified agar plates also formed clear zones on silk fibroin agar plates. Saccharothrix species showed an ability to degrade PLA films and assimilate degradation products in liquid cultures. No significant change of the molecular weight and polydispersity (Mw/Mn) of the remaining film fragments was confirmed. After cultivation for two weeks, many irregular holes/pits on the surface of the film due to the colonization of microorganisms were observed by scanning electron microscopy.Scanning electron micrograph of the surface of PLA film: A. orientalis subsp. orientalis IFO 12362 after 14 d.magnified imageScanning electron micrograph of the surface of PLA film: A. orientalis subsp. orientalis IFO 12362 after 14 d.
Mechanism of Enzymatic Hydrolysis of Poly(butylene succinate) and Poly(butylene succinate‐co‐L‐lactate) with a Lipase from Pseudomonas cepacia
Authors: Taniguchi Ikuo , Nakano Shigeyuki , Nakamura Tetsuro , El‐Salmawy Ahmed , Miyamoto Masatoshi , Kimura Yoshiharu 
Published: February 2003

AbstractEnzymatic hydrolysis of poly(butylene succinate) (PBS) and poly(butylene succinate‐co‐L‐lactate) (PBSL) has been studied by using a lipase originated from Pseudomonas cepacia. It has been found that the drawn fibers of PBSL are readily hydrolyzed by the action of the lipase, while those of PBS undergo little enzymatic hydrolysis. Since the polymer films of PBS and PBSL are readily hydrolyzed under the same conditions, the enzymatic hydrolysis should depend not only on the crystallinity but also on the molecular orientation. The molecular weight of the samples gradually decreases with incubation time, because nonspecific hydrolysis occurs on the main chains of both PBS and PBSL even in the absence of lipase. The enzymatic hydrolysis of PBS and PBSL gives 4‐hydroxybutyl succinate (HBS) as the main product with traces of succinic acid and butane‐1,4‐diol together with L‐lactic acid in the case of PBSL. In addition, the hydrolysis rate of the carboxyl end‐capped PBS is much slower than that of the original or hydroxyl end‐capped PBS. These results imply a hydrolysis mechanism involving the preferential exo‐type chain scission from the carboxyl terminals.Mass remaining of various PBS and PBSL samples as a function of time.magnified imageMass remaining of various PBS and PBSL samples as a function of time.
Enzymatic Ring‐Opening Polymerization of Oxiranes and Dicarboxylic Anhydrides
Authors: Soeda Yasuyuki , Okamoto Takeshi , Toshima Kazunobu , Matsumura Shuichi 
Published: February 2003

AbstractOxiranes, such as glycidyl phenyl ether, benzyl glycidate, glycidyl methyl ether, and styrene oxide, were copolymerized with dicarboxylic anhydrides, such as succinic anhydride, phthalic anhydride, and maleic anhydride, by the action of an enzyme in a stepwise reaction to produce the corresponding polyesters containing some ether linkages having a maximum Mw of 13 500. Oxiranes, such as glycidol and glycidyl phenyl ether, were also homopolymerized and copolymerized with other oxiranes by the enzyme to produce the corresponding polyethers.Enzymatic polymerization of oxiranes and dicarboxylic anhydrides.magnified imageEnzymatic polymerization of oxiranes and dicarboxylic anhydrides.
Effect of Physicochemical Properties of Polyplexes Composed of Chemically Modified PL Derivatives on Transfection Efficiency In Vitro
Authors: Kimura Tsuyoshi , Yamaoka Tetsuji , Iwase Reiko , Murakami Akira 
Published: February 2003

AbstractChemically modified poly‐L‐lysine (PL) derivatives with two essential features, which we have previously reported, have been used to examine the effect of physicochemical properties of their complexes with plasmid DNA on expression efficacy in in vitro gene transfection by osmotic shock procedure. PL derivatives having either Nε‐trimethyl lysine or 13.9% serine residue showed no transfection efficiency. Only when PL was modified in both ways, giving Nε‐trimethyl poly(L‐lysine‐co‐L‐serine), markedly enhanced gene expression was observed. The cellular uptake and localization of DNA in the cells were similar for each cationic polypeptide. The trimethylated polypeptide formed the loosest complexes of DNA among all of the polypeptides used, judging from the loss of EtBr fluorescence. It resulted in more effective DNA release from the complexes by adding heparin, and in the significant gene expression in in vitro transcription/translation systems, as compared with the other polypeptides. The gene transfection efficiency was found to depend on the physicochemical properties of the complexes, such as absence of aggregation, moderate compaction, and easy dissociation, which allow the efficient transcription.Transfection efficiency of pEGFP‐N1 complexes with (○) PL, (•) PLS, (□) PtmL, and (▪) PtmLS at various C/A ratios.magnified imageTransfection efficiency of pEGFP‐N1 complexes with (○) PL, (•) PLS, (□) PtmL, and (▪) PtmLS at various C/A ratios.
Amphiphilic Lipopeptide Microparticles as Contrast Agents for Medical Ultrasound Imaging
Authors: Cuthbertson Alan , Tornes Audun , Solbakken Magne , Moen Ove , Eriksen Morten 
Published: February 2003

AbstractIn this study we investigated the utility of complementary amphiphilic lipopeptides as a new membrane formulation suitable for the preparation of gas‐filled microbubbles. Through primarily ion pairing and hydrophobic interactions we rationalized that the stacking of synthetic lipopeptides into the surface of microbubbles would make bubble suspensions useful as ultrasound contrast agents. By mixing charged lipopeptides in propylene glycol/glycerol solutions in the presence of a perfluorocarbon gas followed by vigorous shaking, microbubble suspensions were formed in good yield with a size distribution spanning the range 1–7 × 10−6m. The microbubbles were studied in an in vivo model and provided imaging efficacy comparable with conventional ultrasound contrast agents.Crude sample (before flotation) of Formulation A analyzed at ×40 magnification. The solid bar indicates 10 × 10−6m.magnified imageCrude sample (before flotation) of Formulation A analyzed at ×40 magnification. The solid bar indicates 10 × 10−6m.
Preparation of Polylactide Microspheres Having Positively or Negatively Charged Surfaces
Authors: Arimura Hidetoshi , Ohya Yuichi , Ouchi Tatsuro , Yamada Hideaki 
Published: February 2003

AbstractThe syntheses of polylactides (PLAs) with branched peptide end groups containing reactive (ionic) moieties such as amino or carboxyl groups are described and were used to prepare PLA‐based microspheres (MSs) with positively or negatively charged surfaces. Branched peptides with hydroxyl end groups and four protected amino or carboxyl groups, Boc4‐K3‐OH or Bn4‐E3‐OH, were synthesized, and the hydroxyl group converted to an alkoxide and was used as the initiation site for the ring‐opening polymerization of L‐lactide. Subsequent deprotection gave PLAs end‐capped with branched peptides having four amino or carboxyl groups, respectively (K3‐PLA and E3‐PLA). K3‐PLA and E3‐PLA were converted to K34+‐PLA and E34−‐PLA by acid or base treatment, respectively. MSs with charged surfaces were then prepared using K34+‐PLA or E34−‐PLA as a surfactant [MS(K34+‐PLA) or MS(E34−‐PLA)]. The ionic surface state of the MSs was confirmed by colloidal titration and zeta potential analysis.
SEM image of MSs: MS(K34+‐PLA).magnified imageSEM image of MSs: MS(K34+‐PLA).
Synthesis and Conformation of Star‐Shaped Poly(γ‐benzyl‐L‐glutamate)s on a Cyclotriphosphazene Core
Authors: Inoue Kenzo , Horibe Shigeru , Fukae Makiko , Muraki Takahito , Ihara Eiji , Kayama Hiroshi 
Published: February 2003

AbstractThe preparation of star‐shaped poly(γ‐benzyl‐L‐glutamate)s by the ring‐opening polymerization of N‐carboxy anhydride γ‐benzyl‐L‐glutamate (BLG‐NCA) with hexakis(4‐aminomethylphenoxy)‐ (4) and hexakis(4‐aminophenoxy)cyclotriphosphazenes (6), and the conformation of resulting polymers has been studied. The six amino groups in 4 can initiate the polymerization of BLG‐NCA to give star‐shaped polyglutamates (7) with narrow molecular weight distributions (Mw/Mn = 1.10–1.33). For the polymerization of BLG‐NCA with 6, however, a high ratio of [BLG‐MCA]/[6] was required to obtain star‐shaped polyglutamates (8). The conformation of 7 changed from a β‐sheet form to a right‐handed α‐helix form, depending on the degree of polymerization per chain (DPn/6). The helix content of hexa‐armed poly (γ‐benzyl‐L‐glutamate‐co‐L‐glutamic acid)s (9), prepared by partial hydrolysis of 7, increased significantly compared with that of the corresponding linear analogue (10). As increasing of helix content of 9, the fluorescence spectra of 8‐anilino‐1‐naphthalenesulfonic acid (ANS), a fluorescence probe, shifted to a short wavelength accompanied by the enhancement of intensity, suggesting that star‐shaped polymers are liable to form hydrophobic domains. From these results and the structural feature of the cyclotriphosphazene core, the formation of a 3α‐helix bundle structure of polyglutamates on both sides of the phosphazene ring has been suggested.
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Control of Enzymatic Degradation of Microbial Polyesters by Plasma Modification
Authors: Ryou Jin‐Ho , Ha Chang‐Sik , Kim Jae‐Won , Lee Won‐Ki 
Published: February 2003

AbstractThe rate of enzymatic degradation of surface‐modified microbial polyesters, poly[(R)‐3‐hydroxybutyrate] and poly[(R)‐3‐hydroxybutyrate‐co‐3‐hydroxyvalerate], was studied. The plasma treatments were carried out in a CF3H or O2 environment. It was found that the CF3H plasma‐treated polyesters exhibited significant retardation of enzymatic erosion because of the surface fluorocarbon groups induced by CF3H plasma. These surface fluorocarbon groups act as retardants on enzymatic degradation due to increased hydrophobicity and of the inactivity of enzymes. However, the increased surface hydrophilicity of polyesters induced by O2 plasma results in no significant acceleration of the enzymatic erosion, which may be due to the thin modified layer.
Weight loss profiles of P(3HB) film exposed to CF3H plasma as a function of plasma exposure time.magnified imageWeight loss profiles of P(3HB) film exposed to CF3H plasma as a function of plasma exposure time.
Synthesis and Characterization of Amphiphilic Biodegradable Copolymer, Poly(aspartic acid‐co‐lactic acid)
Authors: Shinoda Hosei , Asou Yukiko , Suetsugu Akio , Tanaka Kimiko 
Published: February 2003

AbstractAn amphiphilic biodegradable polymer, poly(aspartic acid‐co‐lactic acid) (PAL), was synthesized by simply heating a mixture of aspartic acid (Asp) and L‐lactide without additional catalysts or solvents. The unique branched architecture comprising succinimide units and lactic acid units was confirmed by IR and NMR spectroscopy. A copolymer of sodium aspartate and lactic acid (PALNa) was prepared by reacting PAL with an aqueous sodium hydroxide solution. The PAL was soluble in many organic solvents, while the PALNa was soluble in methanol and water. The hydrolytic degradation behavior of PAL varied with the copolymer composition. A higher Asp content resulted in a faster molecular weight decrease, and introducing glycolic acid units accelerated the degradation rate.
Microphotograph of microsphere of PAL‐1/5.magnified imageMicrophotograph of microsphere of PAL‐1/5.
Surface Hydrophilicities and Enzymatic Hydrolyzability of Biodegradable Polyesters, 2
Authors: Tsuji Hideto , Ishida Takuya 
Published: February 2003

AbstractControl of the surface hydrophilicities and enzymatic hydrolyzability of hydrophobic aliphatic polyesters such as poly(ε‐caprolactone) (PCL) and poly(L‐lactide) [i.e. poly(L‐lactic acid) (PLLA)] was attempted by coating with hydrophilic poly(vinyl alcohol) (PVA). The PVA coating was carried out by immersion of the PCL and PLLA films in PVA solutions. The effects of PVA coating on the hydrophilicities were monitored by dynamic contact angle measurements, while the enzymatic hydrolyzability of the PVA‐coated PCL and PLLA films was evaluated by the weight losses after Rhizopus arrhizus lipase‐ and proteinase K‐catalyzed hydrolysis, respectively. It was found that the PVA coating successfully enhanced the hydrophilicities of the aliphatic polyester films and significantly suppressed enzymatic hydrolyzability of the aliphatic polyester films, excluding the PCL film coated at a very low concentration such as 0.01 g · dL−1 and the crystallized PLLA film coated at 1 g · dL−1, for which slight enhancement and no significant enhancement, respectively, were observed in the enzymatic hydrolyzability. Moreover, the hydrophilicities and enzymatic hydrolyzability of the aliphatic polyester films were controllable to some extent by varying the PVA solution concentration and the film crystallinity.
Advancing contact angle (θa) of PCL, PLLA‐C, and PLLA‐A films before and after the PVA coating by immersion in 1 g · dL−1 solution.magnified imageAdvancing contact angle (θa) of PCL, PLLA‐C, and PLLA‐A films before and after the PVA coating by immersion in 1 g · dL−1 solution.
Poly(amido‐amine)s Carrying Primary Amino Groups as Side Substituents
Authors: Malgesini Beatrice , Verpilio Ilario , Duncan Ruth , Ferruti Paolo 
Published: February 2003

AbstractPoly(amido‐amine)s carrying primary amino groups as side substituents have been obtained by polyaddition of N‐triphenylmethyl‐monosubstituted 1,2‐diaminoethane (TPHMAE) to 2,2‐bisacrylamido acetic acid or 1,4‐bisacryloylpiperazine and subsequent removal of the protecting triphenylmethyl group by treating the resultant polymers with aqueous hydrochloric acid. Soluble polymers can be also obtained directly by the polyaddition of monoprotonated 1,2‐diaminoethane to 2,2‐bisacrylamido acetic acid in the presence of a limited amount of added acetic or hydrochloric acid. The resultant polymers are of a higher molecular weight than the corresponding ones prepared from TPHMAE. By adding a limited amount of N‐triphenylmethyl‐monosubstituted 1,2‐diaminoethane to the monomer mixtures leading to poly(amido‐amine)s with a recognised potential as nonviral vectors, such as ISA 23 and ISA 1, a controlled number of pendant primary amino groups have been introduced. By this procedure, ISA 23 and ISA 1 become suitable as polymer carriers for carboxylated drugs as well as amenable to the labelling techniques by fluorescent probes commonly employed for proteins.Formation of monoprotected primary diamines.magnified imageFormation of monoprotected primary diamines.
Electrochemical studies on the effect of pyrazolo‐containing compounds on the corrosion of carbon steel in 1 M sulphuric acid
Authors: Abd El‐Maksoud S. A. 
Published: February 2003

AbstractThe effect of some synthesized pyrazolo containing compounds on the corrosion of carbon steel in 1 M H2SO4 was investigated. The investigation involved electrochemical polarization methods (potentiodynamic, Tafel extrapolation and the determination of the polarization resistance). A significant decrease in the corrosion rate of carbon steel was observed in the presence of the investigated compounds. The results show that these compounds act as mixed type inhibitors, but the cathode is more preferentially polarized. The relative inhibition efficiency of these compounds depends on both the nature and concentrations of the investigated compounds. Compounds are found to adsorb on the carbon steel surface according to the Langmuir adsorption isotherm.
Korrosionsschäden an Lagertanks für Salzlake
Authors: Burkert A. , Mietz J. 
Published: February 2003

AbstractAn einem Tankbehälter aus dem Werkstoff X2CrNiMo17‐12‐2, der zur Zwischenlagerung von Salzlake für die Käseherstellung dient, wurden trotz langjähriger positiver Erfahrungen an vergleichbaren Anlagen bereits kurze Zeit nach der Inbetriebnahme Lochkorrosionserscheinungen festgestellt. Durch entsprechende elektrochemische Laboruntersuchungen konnte gezeigt werden, dass die vorgefundene Lochkorrosion durch den Einsatz eines Oxidationsmittels zu Desinfektionszwecken verursacht wurde.
Combination of thermal activation and addition of H2O2 to improve cerium‐based immersion treatment of alloy AA5083
Authors: Bethencourt M. , Botana F. J. , Cano M. J. , Osuna R. M. , Marcos M. 
Published: February 2003

AbstractIntensive research has been undertaken in recent years aimed at finding non‐contaminating alternatives to surface treatment processes based on the use of chromates. One of the alternatives proposed involves the use of lanthanide salts, and a variety of methods of protection have been described. In this study, the results of the treatment of samples of alloy AA5083 in a solution of Ce(III) at 323 K and incorporating small quantities of oxygenated water are presented. These results indicate that the application of this type of treatment gives a considerable reduction in the time required for this process and high levels of protection. This time reduction is associated with a combined effect caused, in part by the presence of oxygenated water, which facilitates the formation of islands of cerium, and in part by thermal activation, which facilitates a more rapid development of the alumina film over the metal matrix. Lastly, the results obtained indicate that these treatments provide increased resistance of the alloy against pitting corrosion.
Effect of ferric ions in AISI 316L stainless steel pickling using an environmentally‐friendly H2SO4‐HF‐H2O2 mixture
Authors: Narváez L. , Cano E. , Bastidas J. M. 
Published: February 2003

AbstractA mixture of hydrogen peroxide, sulphuric and hydrofluoric acids has been used as pickling solution at pH 2.0 for AISI 316L austenitic stainless steel (SS). The stability of the H2SO4‐HF‐H2O2 mixture is assessed varying the ferric ions content from 0 to 40 g/L, the temperature from 25 to 60°C, and with and without stirring of the pickling solution. The AISI 316L SS pickling rate at 50°C was 2.6 and 0.2 mg/dm2 day (mdd) in the absence and presence of 40 g/L ferric ions, respectively. p‐toluene sulphonic acid (PTSA) has been used as stabiliser of hydrogen peroxide.
Corrosion resistance of Nd‐Fe‐B permanent magnetic alloys. Part 1: Role of alloying elements
Authors: El‐Aziz A. M. 
Published: February 2003

AbstractThe electrochemical behaviour of Nd‐Fe‐B magnetic alloys was investigated in acid and neutral solutions. The differences in the chemical composition of these materials have distinct influence on the corrosion rate and polarization behaviour. Small additions of cobalt, aluminium and gallium increase the corrosion resistance of the magnetic alloys at high cathodic potential. It was also observed that the increase of hydrogen evolution rate on the surface of the magnetic materials raises the rate of dissolution of these magnets. The electrostatic surface potential was examined by scanning probe microscopy. A relation between the electrostatic surface potential and electrochemical behaviour of these alloys was found. The high values of electrostatic surface potential of the intergranular phases reflect higher corrosion attack. Auger electron spectroscopy was used to analyse the surface layer which formed during anodic polarization of the magnet containing alloying additives. The result indicates the formation of (Nd,Fe)‐oxide with small amounts of cobalt and aluminium.
Fundamental investigation of the degradation laws of aluminide coatings during high‐temperature oxidation
Authors: Liu P. S. 
Published: February 2003

AbstractDuring high‐temperature oxidation, the aluminide coating degrades by two mechanisms, one is the oxidation of the outer surface, and the other is Al diffusion into the substrate. The relevant laws are investigated for coatings on Co‐base superalloys oxidised in air at high temperatures. The driving force mainly comes from the oxidation reaction for the outer degradation layer, and the chemical potential for the inner degradation layer. By an approximation approach, it can be concluded that the life of the outward‐diffusion coating is roughly directly proportional to the second power of the main‐phase thickness of the coating.
Study of electronic‐ionic conducting transformation of temporarily protective oil coating in salt solution
Authors: Zhong Q. , Zhou G. , Xu N. , Rohwerder M. 
Published: February 2003

AbstractIn this paper, a multiple microelectrode array was developed to study the electronic‐ionic conducting transition of temporarily protective oil coating in salt solution. It was pointed out that there existed electronic‐ionic transition of temporarily protective oil coating in salt solution varying with immersion time. At the early stage of immersion, the oil coating was an electronic conductor, which having very low conductivity. With increasing of immersion time, the oil coating transformed from electronic conductor to ionic conductor, where ionic diffusion in the coating was predominant. Based upon Bailey and Ritchie's general electrochemical theory for the oxidation of metals, an electrochemical analysis of potential inhomogeneity of the oil coating was presented. It was assumed that only one step could be rate‐determining in the overall reaction in the metal/oil film/solution system. It was predicted that there were two kinds of film in the temporarily protective oil coating, ionic and electronic conducting film. For the ionic conducting film, potentials of oil coated electrode were equal to equilibrium potential of metal oxidation at the metal/coating interface (Eaeq), and it had the most negative value. For the electronic conducting film, potentials obtained were equal to the equilibrium potential of the oxidant reduction at the coating/electrolyte interface (Eceq), and it had the most positive value. Potential measurements in this paper verified the results of Wormwell and Brasher's research in 1949; the distribution of potential on oil‐painted wire beam electrodes being heterogeneous and following a discontinuous binomial probability distribution were also elucidated.