bluuebunny/crossref_metadata_2025_split huggingface dataset:
Farmers' perceptions of erosion by wind and water in northern Burkina Faso
Authors: Visser S. M. , Leenders J. K. , Leeuwis M. 
Published: January 2003

AbstractWind and water erosion are widespread phenomena throughout the Sahel, especially in the early rainy season, when high‐intensity rainstorms are often preceded by severe windstorms. This paper describes the results of a survey on the farmers' perceptions of wind and water erosion processes and control measures. In three villages in northern Burkina Faso, 60 farmers were interviewed using semi‐structured questionnaires. According to most of the farmers, wind‐blown particle transport has an influence on the fertility and the infiltration capacity of the soils. They considered wind‐blown particle transport damaging for their crops. Seedlings are damaged by scouring grains of sand or lost when buried in sand deposits. Only 32 per cent of the farmers observed runoff and 15 per cent observed erosion and deposition during periods of high intense rainfall. According to 22 per cent of the farmers intense rainfall has a negative effect on crop production. Plants die because of the effects of stagnating water and plants are damaged by the forces of flowing water.All farmers are familiar with techniques to reduce soil erosion and 96 per cent applied one or more of these techniques. The indigenous techniques are application of manure and mulch. The main constraints to apply these techniques are lack of labour, manure and mulch. New techniques introduced by agricultural organizations are zaï (a traditional agricultural practice whereby pits of diameter 10–15 cm are filled with compost for sowing) and half‐lines, stone rows and sand ridges.Farmers have a good knowledge of wind erosion processes, but do not report the effects of water erosion processes. The farmers are willing to apply new techniques to control soil erosion, but the main constraints to apply these measures are insufficient knowledge and lack of labour. Copyright © 2002 John Wiley & Sons, Ltd.
The causes and spatial pattern of land degradation risk in southern Mauritania using multitemporal AVHRR‐NDVI imagery and field data
Authors: Thiam A. K. 
Published: January 2003

AbstractMultitemporal 1 km NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) maximum composite imagery was utilized in combination with rainfall, soil types, and field survey data on dominant rural activities to assess the risk of land degradation in southern Mauritania. Mauritania is one of eight continental West African Sahel countries that stretch from Chad to the northwestern Atlantic coast, and from the southern fringe of the Sahara Desert to the northern limit of the Sudanian climatic zone. The major environmental problem these countries are currently facing is the temporally and spatially erratic character of rainfall, frequently leading to general or local droughts since the late‐1960s with subsequent increase of human pressure on the natural resource base and degradation. Image deviation was applied to maximum NDVI composites of the growing season (June to October) for the period 1990–99 to detect temporal and spatial change patterns over the study area. Only pixels whose values were lower than their temporal mean minus 0ċ5 standard deviation were retained as areas under threat. These were combined with soil types and the spatial pattern of deforestation (fuelwood and building material collection areas) grazing, and agricultural land to determine the causes of lowering primary biological productivity. The results show that the below‐normal NDVI values generally coincide with the patterns of below‐normal rainfall: deforestation, and overgrazing areas, agricultural land, and low primary biological productivity soil types. Thus the observed substantial decrease in biomass production results from the combined impacts of frequent rainfall deficits and uncontrolled resource‐base exploitation by the local population. Large chunks of land that show consistent low biomass production are also observed on unproductive soils. Finally, the below‐normal rainfall, below‐average NDVI values, and human impacts images were cross‐classified to produce a three‐class (low, moderate, and high) land degradation risk map along with a table containing the area covered by each class. A Boolean mask of the degradation risk map applied to the soils map showed that all soil types in southern Mauritania are at risk of degradation. These products could serve as a strong basis for decision making in regard to planning resource allocation for environmental rehabilitation. Copyright © 2002 John Wiley & Sons, Ltd.
Local innovation in a global context: documenting farmer initiatives in land husbandry through WOCAT
Authors: Critchley W. R. S. , Mutunga K. 
Published: January 2003

AbstractInnovation by farmers in land husbandry was the focus of the project Promoting Farmer Innovation (PFI), which was operational in Kenya, Tanzania and Uganda from 1997 to 2001. One of the project's final activities was to document best‐bet innovations. It was decided to make use of a questionnaire available under the World Overview of Conservation Approaches and Technologies (WOCAT) to collect data on a selection of these technologies. Data were fed back into WOCAT's global database. Eighteen technical initiatives were recorded in this way, and the findings added to existing data and in‐house knowledge. This information was analysed and a technical report produced (Mutunga and Critchley, 2001). The technologies included turning gullies into gardens, digging planting pits for millet and sorghum and harvesting water from roads. Each combined aspects of land conservation with improved plant production. While several required relatively high initial labour input, all were considered economically beneficial by the farmers. Adoption by other farmers was generally rapid, partially as a result of farmer to farmer visits under PFI. The value of the PFI‐WOCAT exercise was not restricted to recording and disseminating information, however. It was also a test of the utility of WOCAT within a project. There were a number of interesting findings. Although those who filled the questionnaires found it an onerous task, they felt that they learned a good deal as they went through the process. One of the main conclusions was that the questionnaire could be a very valuable template to help guide internal monitoring and evaluation, if used from the start of a project intervention. Copyright © 2002 John Wiley & Sons, Ltd.
Exploring environmental causes of altered ras effects: Fragmentation plus integration?
Authors: Porta Miquel , Ayude Daniel , Alguacil Juan , Jariod Manuel 
Published: January 2003

AbstractMutations in ras genes are the most common abnormality of oncogenes in human cancer and a major example of activation by point mutation. Experimental and epidemiological studies support the notion that Ki‐ras activation and expression may be chemically related. We discuss the potential role of several environmental compounds in the induction or promotion of ras mutations in humans, with a focus on exocrine pancreatic cancer, the human tumor with the highest prevalence at diagnosis of Ki‐ras mutations. Organochlorine compounds, organic solvents, and coffee compounds may play an indirect role in causing Ki‐ras mutations, rather than as direct inducers of the mutations. Although for some organochlorine compounds the induction of point mutations in ras oncogenes cannot be excluded, it seems more likely that the effects of these compounds are mediated through nongenomic or indirectly genotoxic mechanisms of action. Organic solvents also may act via enzymatic induction of ras mutagens or by providing a proliferation advantage to ras‐mutated cell clones. In exocrine pancreatic cancer, caffeine, other coffee compounds, or other factors with which coffee drinking is associated could modulate Ki‐ras activation by interfering with DNA repair, cell‐cycle checkpoints, and apoptosis. Asbestos, cigarette smoking, and some dietary factors also may be involved in the initiation or the promotion of Ki‐ras mutations in lung and colon cancers. Further development of the mechanistic scenarios proposed here could contribute to a meaningful integration of biological, clinical, and environmental knowledge on the causes of altered ras effects. © 2003 Wiley‐Liss, Inc.
Exceptional activity of murine glutathione transferase A1‐1 against (7R,8S)‐dihydroxy‐(9S,10R)‐epoxy‐7,8,9,10‐tetrahydrobenzo[a]pyrene–induced DNA damage in stably transfected cells
Authors: Guo Jianxia , Pan Su‐Shu , Singh Shivendra V. 
Published: January 2003

AbstractWe have shown previously that the alpha class murine glutathione transferase (GST) isoenzyme mGSTA1‐1, unlike other mammalian class alpha GSTs, is highly efficient in catalyzing the glutathione (GSH) conjugation of (7R,8S)‐dihydroxy‐(9S,10R)‐epoxy‐7,8,9,10‐tetrahydrobenzo[a]pyrene [(+)‐anti‐BPDE], which is the ultimate carcinogenic metabolite of benzo[a]pyrene. The present studies were undertaken to determine the efficacy of mGSTA1‐1 in cellular protection against (+)‐anti‐BPDE‐induced DNA damage in HepG2 cells stably transfected with mGSTA1 cDNA. Untransfected HepG2 cells, vector‐transfected HepG2 cells (HepG2‐vector), and cells transfected with mGSTA4 cDNA (HepG2‐mGSTA4), an alpha class murine GST isoenzyme with low (+)‐anti‐BPDE‐GSH conjugating activity, were used as controls for comparison. Intracellular GSH conjugation of (+)‐anti‐BPDE was significantly higher in mGSTA1‐1–overexpressing HepG2 cells (HepG2‐mGSTA1) than in HepG2‐vector or HepG2‐mGSTA4 cells. The formation of DNA‐adducts of (+)‐anti‐BPDE, following a 10‐, 20‐, or 30‐min exposure to 0.1, 0.5, or 1.0 μM [3H](+)‐anti‐BPDE, was reduced significantly in cells transfected with mGSTA1‐1 compared with HepG2‐vector or untransfected HepG2 cells. Consistent with the results with purified protein, overexpression of mGSTA4‐4 had no effect on (+)‐anti‐BPDE–induced DNA damage. The results of the present study indicated that mGSTA1‐1 was exceptionally effective in affording protection against (+)‐anti‐BPDE–induced DNA damage in a cellular system. © 2003 Wiley‐Liss, Inc.
New scope for synthesis of divinyl ether and maleic anhydride copolymer with narrow molecular mass distribution
Authors: Volkova I. F. , Gorshkova M. Yu. , Ivanov P. E. , Stotskaya L. L. 
Published: January 2003

AbstractThe alternating copolymer of divinyl ether and maleic anhydride (DIVEMA) possesses diverse biological activity and uses for production of drug delivery systems. DIVEMA's biological effects are determined by molecular mass, therefore it is necessary to have information about copolymer molecular mass and its distribution. A direct method for gel permeation chromatography analysis of DIVEMA molecular mass characteristics in aqua solution without any preliminary modification was developed. The effect of a number of factors (the concentration of monomers and their ratios, the concentration of initiator, the nature of the solvents) on DIVEMA's solution properties and molecular mass distribution was studied by gel permeation chromatography and viscometry. The approach to synthesis of DIVEMA with narrow molecular mass distribution was designed. The substantial influence of water on DIVEMA molecular mass characteristics was determined. The proposal was made that water may play a part in the formation of charge‐transfer complexes playing a significant role in copolymerization. Copyright © 2003 John Wiley & Sons, Ltd.
“Length and breadth” polyrotaxane structures—a new concept in three‐dimensional polymeric systems
Authors: Azzam T. , Peppas N. A. , Slomkowski S. , Domb A. J. 
Published: January 2003

AbstractThis work describes the synthesis and characterization of rotaxane‐crosslinked polymers using macrocyclic poly(ethylene glycol) (PEG) attached to a vinyl moiety. Diacyl chlorides (fumaryl or itaconyl) and PEG400 were condensed under high dilution conditions to yield the corresponding macrocyclic monomers. These were purified by column chromatography and identified by mass spectroscopy utilizing MALDI‐TOF technique and 1H‐NMR. Radical polymerization in bulk of these macrocyclic monomers using benzoyl peroxide as initiator, resulted in soft polymers which are soluble in various organic solvents. Under the same conditions, insoluble gels were obtained by copolymerization of the ring‐substituted vinyl monomers with either hydrophobic vinyl monomers (methyl methacrylate, MMA) or with a hydrophilic vinyl monomer (2‐hydroxy ethyl methacrylate, HEMA). These results indicate that crosslinking was obtained due to threading of linear chains through macrocycles which act as crosslinkers. The swelling ratios of the gels indicated a correlation between the molar ratios of the macrocycle and the linear chain incorporated with it. Copyright © 2003 John Wiley & Sons, Ltd.
Syntheses of biodegradable (multi) block copolymers, star‐shaped polyesters and networks via ring‐expansion polymerization
Authors: Kricheldorf Hans R. 
Published: January 2003

AbstractNumerous cyclic dibutyltin alkoxides were prepared by condensation of Bu2Sn(OMe)2 with various short or long α,ω‐diols. Insertion of lactones or lactide into the SnO bonds resulted in ring‐expansion polymerizations which allowed a control of the ring size (chain length) via the monomer initiator ratio. When the cyclic initiators were derived from a long α,ω‐diol, such as poly(tetrahydrofuran)diols or polysiloxane diols, the resulting cyclic polylactones were necessarily cyclic triblock copolymers. The high nucleophilicity of the Sn‐O bond enabled ring‐opening polycondensations with dicarboxylic acid dichlorides yielding multiblock copolyesters. Condensations with monocarboxylic acids yielded functionalized A‐B‐A triblock copolymers. Polycondensation with trifunctional acid chlorides yielded biodegradable networks. Hydroxyethylated pentaerythritol condensed with Bu2Sn(OMe)2 yielded a spirocyclic initiator. Ring‐expansion polymerization with lactones followed by acylation with carboxylic acid chlorides produces star‐shaped polylactones having functional endgroups. Biodegradable networks were also obtained when bisstannylenated α‐glucose methyl glycoside was used as initiator for ϵ‐caprolactone, and when the resulting spirocyclic polylactone was polycondensed with sebacoyl chloride. Copyright © 2003 John Wiley & Sons, Ltd.
The system polyamide/sulfamate/dipentaerythritol: flame retardancy and chemical reactions
Authors: Lewin Menachem , Brozek Jiri , Martens Marvin M. 
Published: January 2003

AbstractThe use of sulfur compounds and particularly sulfamates for flame‐retarding cellulose and other polymers is reviewed. Recent results on flame‐retarding polyamides in this laboratory are presented. The system developed requires the use of 1.5–2.5 wt% of ammonium sulfamate (AS) or diammonium imidobisulfonate (DIBS) together with 0.4–0.85 wt% of pentaerythritol (petol) or dipentaerythritol (dipenta) to obtain fully flame‐retardant polyamide 6 and 66. The properties of the flame‐retarded products, obtained both by Brabender mixing and by twin‐screw extrusion are: UL‐94 rating of V‐0 on bars of 1/16″ and 1/32″; no flaming drips; very low burn time; tensile strength of 11 KPSI; 10–20% elongation and CTI values of ca. 600 V. Thermoanalytical and FTIR data are presented that indicate the thermal stability of the system and the chemical reactions occurring. Mechanisms are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Molecular mass distribution of polycations and dextrans by high‐performance size exclusion chromatography
Authors: Kumar Neeraj , Azzam Tony , Domb Abraham J. 
Published: January 2003

AbstractA high‐performance size exclusion chromatographic (HPSEC) method for molecular mass distribution (MMD) was developed for polycations. Results obtained from HPSEC using UV and RI detectors were compared with the viscosity measurements. Pullulan standards were used for Mw calibration. It is concluded that HPSEC with a UV detector offers a sensitive and simple method that has the required accuracy. Degradation studies following this method indicate that dextrans are stable at a temperature of 55 °C and at different pH solutions for up to 7 days. Copyright © 2003 John Wiley & Sons, Ltd.
Direction‐sensitive stress measurements with carbon nanotube sensors
Authors: Zhao Qing , Frogley Mark D. , Wagner H. Daniel 
Published: January 2003

AbstractSingle‐wall nanotubes (SWNTs) embedded in polymer can be used as mechanical sensors because the position of the D* Raman band of SWNTs is strongly dependent on the strain transferred from the matrix to the nanotubes. In order to detect the stress (or strain) information in specific directions, polarized Raman spectroscopy is used to select out the signal from the nanotubes that are parallel to the polarization direction. This method is demonstrated by measuring the stress distribution around a circular hole in the SWNT/polymer composites under uniaxial tension. Then the stress field in a polymer matrix in the vicinity of a single glass fiber is mapped on the micrometer scale. A stress concentration zone is observed around the fiber end. The importance of this technique and the measurements for composite design and micro‐mechanical models is discussed briefly. Copyright © 2003 John Wiley & Sons, Ltd.
Ion‐doping role in photoinduced processes in pyridine‐containing polymeric viscous solutions
Authors: Vaganova Evgenia , Meshulam Gilia , Kotler Zvi , Yitzchaik Shlomo 
Published: January 2003

AbstractThe photochemical reaction in poly(4‐vinyl pyridine)/pyridine compositions under irradiation at 254 nm results in new electronic and structural properties. Photoinduced electronic and structural properties can be assigned to the appearance of the pyridine ring‐opening photoproducts and interaction of the latter between themselves and with pyridine moieties. Doping of the composition with hydrochloric acid or lithium chloride can control the photochemical reaction, especially the interaction of the ring‐opening photoproducts. The cleaved form of the compounds and the aggregates of the latter act as the crosslinkers in the system. Optical property changes are followed by structural changes. Depending on the doped compound, different long‐wave‐shifted emissions arise in the compositions after irradiation. The far long‐wave‐shifted emission appears in the system doped with lithium chloride, ­which is unstable and disappears shortly after cessation of irradiation, while the red‐emitting centers of the undoped system are stable and exhibit a second harmonic generation (SHG) signal. Copyright © 2003 John Wiley & Sons, Ltd.
Polymeric biomaterials synthesized by radiation techniques – current studies at IARC, Poland
Authors: Ulanski Piotr , Janik Ireneusz , Kadlubowski Slawomir , Kozicki Marek , Kujawa Piotr , Pietrzak Miroslaw , Stasica Przemyslaw , Rosiak Janusz M. 
Published: January 2003

AbstractFor over 15 years the Institute of Applied Radiation Chemistry in Lodz, Poland, has been involved in studies on new polymeric biomaterials. Some of the technologies developed employ radiation techniques for the synthesis of crosslinked products (mainly hydrogels), for surface modification and for sterilization. An example of a mature technology of this kind is hydrogel wound dressings, now being produced on a large scale and available on the market in many Central European countries. Another advanced project is a hydrogel system for healing endometrium cancer by precise, local drug delivery. Preliminary clinical tests with over 70 patients have been completed with very good results.Current research projects, besides further development of the above mentioned systems, include: a hydrogel‐based system for local, controlled drug delivery; polymer materials for encapsulation of living cells and for the construction of hybrid artificial organs; a new approach to the synthesis of polymeric material for intervertebral disc implant; temperature‐sensitive membranes and supports for cell cultures; hydrogel phantoms for low‐dose, three‐dimensional radiation dosimetry; degradation‐resistant nanogels and microgels for biomedical purposes (e.g. synovial fluid substitute); hydrogel‐based dietary products and adjustment of the molecular weight of biopolymers by ultrasound and ionizing radiation. Copyright © 2003 John Wiley & Sons, Ltd.
Conductive polymer composites (CPCs): comparison of electrical properties of poly(ethylene‐co‐ethyl acrylate)‐carbon black with poly(butylene terephthalate)/poly(ethylene‐co‐ethyl acrylate)‐carbon black
Authors: Feller J. F. , Linossier I. , Levesque G. 
Published: January 2003

AbstractWe have studied the influence of the addition of poly(butylene terephthalate) (PBT) to poly(ethylene‐co‐ethyl acrylate)‐carbon black (EEA‐CB) on the electrical properties of the blends, namely the resistivity and power dissipation of the monophasic and diphasic systems. The morphology of the latter blend is characterized by two interpenetrated immiscible phases which provide a good thermal stability to the composite up to at least 170 °C. Power can be regularly delivered without a negative temperature coefficient (NTC) effect at 100 °C where poly(ethylene‐co‐ethyl acrylate) melts. However, the significant decrease of positive temperature coefficient (PTC) amplitude compared to the monophasic systems reduces the self‐regulating heating ability. The PTC effect amplitude decrease was studied by some of its known origins (thermal expansion, melting of crystalline phase, carbon black localization). Correlation of the composites resistivity with linear expansion, the melting process of EEA, and the volume expansion of PBT, show that none of these parameters can alone explain the electrical properties' evolution with temperature. Our interpretation of the PTC effect amplitude decrease is based on the PBT matrix lower thermal expansion and on the increased carbon black content located at the interface. Copyright © 2003 John Wiley & Sons, Ltd.
Polyanhydrides with hydrophobic terminals
Authors: Krasko Michal Y. , Shikanov Ariella , Kumar Neeraj , Domb Abraham J. 
Published: January 2003

AbstractPolyanhydrides prepared from hydrophobic diacids such as sebacic acid (SA) are brittle and unstable in storage and degrade with time. The physical properties of these polyanhydrides have been improved by introducing hydrophobic terminals into the main chain which has provided better stability and controlled the molecular weight. The effects of molecular weight, pliability, biodegradation and drug release on polymer were investigated. Poly(sebacic anhydride) (PSA) was terminated with the unsaturated fatty acids, ricinoleic acid, oleic acid, linoleic acid and the cholesterol derivative, lithocholic acid, and prepared in the weight ratio of 70:30. Polymers thus obtained had a predictable molecular weight of 3–8 × 103 and an Mp of 60–76 °C and degraded at the rate of 3.3–7.6 mg/cm2/day. The rate of degradation was dependent on the contents of the hydrophobic terminals. These polyanhydrides were found to be useful for the release of hydrophobic and hydrophilic drugs for 2–3 weeks in vitro. Copyright © 2003 John Wiley & Sons, Ltd.