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  • 1
    Electronic Resource
    Electronic Resource
    Unsaturated Zone and Ground-Water Contamination by Organic Pollutants in a Sewage-Effluent-Irrigated Site (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 31 (1993), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: This study describes the distribution of organic pollutants from the ground surface, through the unsaturated zone, to the water table at a citrus grove irrigated by sewage effluent for about 20 years. The citrus grove, located in Israel, overlies an unconfmed Coastal Plain aquifer about 2 km inland from the Mediterranean Sea. The distribution of organic compounds at the citrus grove is compared with two control sites receiving moisture from nonpolluted water sources (one in another citrus grove irrigated by ground water and the other in an uncultivated area receiving only precipitation). Overall, 10 analyses were performed. At the effluent-irrigated site, organic pollutants from the sewage had migrated through the 20 meter thick unsaturated zone to the water table; included in these were several pollutants, such as toluene and phthalates, that are considered to be biodegradable. Pollutant concentrations generally increased with depth. On the other hand, pollutant concentrations at the two control sites decreased significantly with depth through the unsaturated zone. The downward mobility of organic pollutants may be enhanced by the sewage itself. Because sewage effluent is considered to be a readily available source of irrigation water in many parts of the world, the results of this study suggest that what may seem to be a relatively simple solution to water scarcity problems may have potentially long-term and dangerous effects on ground-water quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1993.tb00588.x
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of biodegradable aromatic anhydride copolymers (1992)
    s.l. : American Chemical Society
    Macromolecules 25 (1992), S. 12-17 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00027a003
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  • 3
    Electronic Resource
    Electronic Resource
    The impact of selective logging on forest structure and tenrec populations in western Madagascar (1990)
    Springer
    Oecologia 84 (1990), S. 126-133 
    Details
    ISSN: 1432-1939
    Keywords: Madagascar ; Selective logging ; Vegetation structure ; Tenrecs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary This paper reports on possible effects of selective logging on vegetation structure and its consequences for two tenrec species in a dry forest in western Madagascar. On a small scale semi-mechanized logging of less than 10 m3 per ha alters forest structure significantly. However on a large scale most of these changes are smaller than the variation of forest structure due to natural causes. The most profound ecological effect of logging is a reduction in the number of woody species in the regenerating cohort of trees. Potential longterm consequences of this feature are discussed. Microhabitat variables influencing the habitat utilization of two tenrec species,Echinops telfairi andTenrec ecaudatus, were identified in an area of unlogged forest. The conclusions derived from this analysis were then tested in other parts of the forest which had been modified by selective logging. Logging of the extent described above slightly impairs habitats forE. telfairi but has no effect onT. ecaudatus. Though the latter species is hunted extensively in the logged areas, loggingper se does not threaten the survival of either species.
    Notes: Résumé Cette étude met en évidence quelques effets de l'exploitation séléctive de la forêt sur la structure de la végétation et les conséquences pour deux espèces de tenrecs dans une forêt sèche à l'ouest de Madagascar. Dans un domaine limité, l'exploitation de bois de moins de 10 m3 par ha change considérablement la structure de la forêt. Mais si on considère une échelle plus grande, ces effets sont inférieurs à la variabilité naturelle. L'effet le plus grave de l'exploitation forestière sélective est la reduction du nombre d'espèces végétales ligneuses dans le processus de regénération naturelle de la forêt. Quelques conséquences possibles de cette réduction pour les animaux sont discutées. Quelques caractères distinctifs de la végétation qui influencent l'utilisation de l'habitat par deux espèces de tenrec,Echinops telfairi etTenrec ecaudatus, ont été identifiés dans une partie de la forêt qui n'a pas encore été exploitée. Les conclusions de cette analyse sont vérifiées dans une autre partie de la forêt qui a été modifiée par l'exploitation du bois. L'exploitation forestière sélective du bois détériore légèrement l'habitat pourE. telfairi, mais elle n'a pas d'effets remarquables surT. ecaudatus. L'exploitation sélective du bois favorise la chasse par l'ouverture de chemins d'accès. La chasse deT. ecaudatus est particulièrement intense, mais cependant ni l'une ni l'autre des espèces de tenrec considérées ne sont en danger d'extinction par cette form d'exploitationper se.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665606
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  • 4
    Electronic Resource
    Electronic Resource
    Chemical Interactions Between Drugs Containing Reactive Amines with Hydrolyzable Insoluble Biopolymers in Aqueous Solutions (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 865-868 
    Details
    ISSN: 1573-904X
    Keywords: polyanhydrides ; poly(lactic acid) ; amidation ; drug interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Chemical reactions between drugs containing reactive amines with hydrolyzable polymers in buffer solutions were investigated. Phenylalkylamines with increasing nucleophilic reactivity were used as model drugs. Solutions of phenylalkylamines were reacted heterogeneously with representative biodegradable polyanhydride and polyester powders in various pH solutions, and the recovery of the amines from the solutions was determined. Poly(sebacic acid), a reactive polyanhydride, reacted by amide formation with the tested amines and their respective HC1 salts when exposed to physiologic pH (pH 7.4). However, at pH 5.0 no interaction occurred. The aromatic polyanhydride, PCPP, and the polyesters based on lactic acid and caprolactone did react with the amine derivatives at pH 7.4, but at a slower rate. The reaction can be avoided with appropriate salt derivatives of the amines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018985909777
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  • 5
    Electronic Resource
    Electronic Resource
    Absorbable biopolymers derived from dimer fatty acids (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1275-1285 
    Details
    ISSN: 0887-624X
    Keywords: biodegradable polymers ; polyanhydride ; dimer fatty acid ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new class of aliphatic copolyanhydrides was synthesized from nonlinear hydrophobic dimers (FAD) of erucic acid and sebacic acid which possessed the desired physico-chemical and mechanical properties for use as a carrier for drugs. The polymers were synthesized by melt condensation to yield film-forming polymers with molecular weights of 250,000. The copolymer composition was determined by 1H-NMR and gravimetric methods. In vitro degradation studies showed that these polymers degrade following a first-order kinetics with a rapid degradation in the first 10 days leaving a residue which is mostly the FAD comonomer. The drug release from the polymer also followed a first-order kinetics which correlates with the degradation process of the polymer. Drugs like carboplatin, methotrexate, tetracycline, and gentamicin were released in vitro for over 2 weeks and in some cases over 6 weeks. In vivo biocompatibility tests in rats and rabbits in the brain, muscle, and subcutaneously, demonstrated their toxicological inertness and biodegradability. The 1 : 1 copolymer of FAD : SA was selected as a carrier for various applications including a gentamicin-releasing implant which is now undergoing human clinical trials for the treatment of osteomyelitis. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310523
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  • 6
    Electronic Resource
    Electronic Resource
    Polyanhydrides. IV. Unsaturated and crosslinked polyanhydrides (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 571-579 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Unsaturated polyanhydrides of the structure —[—(—CO—CH=CH—COO—)x—(—CO—R—COO—)y—]n—, were synthesized. The polymers were prepared by either melt or solution polycondensation. Weight average molecular weights of up to 30,000 were obtained. The double bonds remain intact throughout the polymerization process and were available for a secondary reaction to form a crosslinked matrix. Poly(fumaric acid) is crystalline and insoluble in common organic solvents. Copolymers of fumaric acid with aliphatic diacids are less crystalline and soluble in chlorinated hydrocarbons. These copolymers displayed nearly constant degradation rates and drug release rates under physiological conditions. The time for complete degradation of 14 × 1.5 mm discs of poly(fumaric anhydride) and poly(sebacic anhydride) occurred in 2 and 15 days, respectively, while their copolymers degraded within this range. Further crosslinking of the polyanhydrids is demonstrated.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290413
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  • 7
    Electronic Resource
    Electronic Resource
    Degradable polymer blends. I. Screening of miscible polymers (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1973-1981 
    Details
    ISSN: 0887-624X
    Keywords: polymer blends ; biodegradable polyesters ; polyanhydrides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Blends of biodegradable polymers having properties distinct from the individual polymer components, and that are suitable for use as carriers of pharmaceutically active agents, were prepared from two or more polyanhydrides, polyesters, and mixtures of polyanhydrides and low molecular weight polyesters. The blends have different properties than the original polymers, providing a mean for altering the characteristics of the polymeric matrix without altering the chemical structure of the component polymers. Aliphatic, aromatic, and copolymers of polyanhydrides were miscible in each other and formed less crystalline compositions with a single melting point which was lower than the melting point of the starting polymers. The polyesters: poly(lactide-glycolide), poly(caprolactone), and poly(hydroxybutyric acid) presented some miscibility in each other. However, the polyanhydrides were immiscible with the polyesters resulting in a complete phase separation both in solution or in melt mixing. Only low molecular weight polyesters (in the range of 2000) of lactide and glycolide, mandelic acid, propylenefumarate, and caprolactone presented some miscibility with polyanhydrides. Similarly, poly(orthoester) and hydroxybutyric acid polymers formed a uniform mixture with the anhydride polymers which had the two melting points of the original polymers. Drug release from polymer blends composed of poly(hydroxybutyric acid) or low molecular weight poly(lactic acid) with poly(sebacic anhydride) (PSA) showed a constant release of drug for periods from 2 weeks to several months as a function of the PSA content in the blend. Increasing the content of PSA, a fast degrading polymer, increases the release rate from the blend. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310805
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  • 8
    Electronic Resource
    Electronic Resource
    The formation of propylene fumarate oligomers for use in bioerodible bone cement composites (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 973-985 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(propylene fumarate) (PPF) oligomers were synthesized by step polymerization using bis(2-hydroxypropyl fumarate) or propylene bis(hydrogen maleate) as starting materials. Oligomers possessing identical degrees of polymerization (DP), but varying in their end group character (either hydroxyl or carboxyl) were first prepared and characterized, then used as part of a bone cement preparation consisting of oligomer, tricalcium phosphate, calcium carbonate, and methyl methacrylate. Compressive strength of the resulting composite appeared to be dependent on both the degree of polymerization of the PPF, and the nature of the oligomers' end groups.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280503
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular Weight Changes in Polymer Erosion (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 1279-1283 
    Details
    ISSN: 1573-904X
    Keywords: drug delivery system ; erodible polymers ; polyanhydrides ; induction period ; molecular weight
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We report a study of the effects of polymer molecular weight on the erosion of polyanhydride copolymer matrices composed of 1,3-bis (p-carboxyphenoxy)-propane (CPP) and sebacic acid (SA) in aqueous solution. The erosion profile characteristically displays an induction period during which the erosion rate is relatively slow. The length of this period depends on the initial molecular weight of the polymer. The induction period may be characterized as a time during which a rapid decrease in polymer molecular weight occurs, the end of this period correlating with the time required for the polymer molecular weight to decrease to below a value of approximately 5000 (MW).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015801216466
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  • 10
    Electronic Resource
    Electronic Resource
    Stimulation of trigeminal motoneurons by in vivo implantation of glutamate-impregnated microspheres (1992)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 3 (1992), S. 337-344 
    Details
    ISSN: 1042-7147
    Keywords: Polyanhydride ; Microsphere ; Glutamate ; Trigeminal ; Motoneuron ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The objective of this study was to alter biomechanical forces generated by the muscles of mastication that affect the growth of the craniofacial skeleton through the implantation of neurotransmitter microspheres to stimulate trigeminal motoneurons (TMNe) in vivo. Polyanhydride microspheres containing L-glutamate were stereotaxically implanted 170-920 μm rostral to the left-side trigeminal motor nucleus (TMNu) in 17 Sprague-Dawley rats at 33-38 days old. Seven rats received blank-microsphere implants and two rats had empty delivery system penetration as controls. All rats were killed 10-14 days postsurgical for dissection, brain histology, osteometric data, and SEM analyses. Dimensions of the facial skeletons of glutamate-microsphere rats showed significant (P〈0.01, P〈0.05) differences when compared to control animals. Glutamate-microsphere animals also demonstrated significant (P〈0.01) differences between the dimensions of their implant-and nonimplant-side facial skeletons. SEM analyses indicated that glutamate-microsphere rats had greater implant-side wear of their mandibular incisors compared to blank-microsphere or delivery system controls. The skeletal alterations in the glutamate-microsphere rats are hypothesized to be due to increased implant-side TMNe and masticatory muscle activity patterns.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1992.220030609
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