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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 47 (1991), S. 945-948 
    ISSN: 1420-9071
    Keywords: Juvenile hormone ; Manduca sexta ; Lepidoptera ; immunotaxonomy ; monoclonal antibodies ; hemolymph
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The hemolymph from various species of moths was analyzed for cross-reactivity with a panel of six monoclonal antibodies made against the hemolymph juvenile hormone binding protein ofManduca sexta. With the exception of one antibody, the immunoreactivity was limited to the sphingid family. One monoclonal antibody cross-reacted with a number of lepidopteran species; however, families such as Noctuidae and Pyralidae, known to have high affinity, low molecular weight juvenile hormone binding proteins, did not cross-react. Immunological cross-reactivity withManduca sexta juvenile hormone binding protein in several primitive moth families supports the current model of phylogenetic relationships in the order Lepidoptera.
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  • 2
    ISSN: 1573-1561
    Keywords: Linear furanocoumarins ; Spodoptera exigua ; Lepidoptera ; Noctuidae ; UV light ; tritrophic interactions ; Bacillus thuringiensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Acidic fogs with a pH of 2.0 and duration of 2 hr did not reduce the efficacy ofBacillus thuringiensis var.Kurstaki (Berliner). Therefore, the impact of UV radiation was investigated on the interactions between (1) levels of the antibacterial linear furanocoumarins psoralen, bergapten, and xanthotoxin inApium graveolens (L.) occurring following a 2.0 pH acidic fog episode, (2) the noctuidSpodoptera exigua (Hübner), and (3) a sublethal dosage of the microbial pathogenB. thuringiensis var.Kurstaki. Mean time to pupation in the absence of UV radiation (survival was too low to conduct this analysis for insects exposed to UV) was significantly extended by the addition of either psoralens orB. thuringiensis. Larvae developing on diets containingB. thuringiensis plus psoralens required nearly 40% longer to pupate than controls, but their effects were additive as the interaction was not significant. Although the mean times to adult emergence were significantly different, time spent in the pupal stage did not vary significantly between treatments, indicating that increases in larval developmental time were responsible for the observed decrease in developmental rate. Mean time to mortality, a weighted average time of death, was not significantly affected by any of the treatments. In a 2 × 2 × 2 factorial analysis, all main effects (linear furanocoumarins.B. thuringiensis, UV radiation) reduced survival significantly, as did the three-way interaction. Thus, antagonistic interactions with psoralens that would reduce the effectiveness ofB. thuringiensis in the field were not observed. When pairs of main effects were nested within the two levels (presence and absence) of the third factor, several two-way interactions were found. Interestingly, the activity ofB. thuringiensis and the psoralens, individually or in combination, was enhanced by exposure to UV radiation. Implications of this research are discussed for both natural and agricultural ecosystems.
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  • 3
    ISSN: 0887-624X
    Keywords: thermoplastic elastomer ; carbocationic polymerization ; polyisobutylene ; living polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New linear triblock thermoplastic elastomers (TPEs) comprising a rubbery polyisobutylene (PIB) midblock flanked by two glassy endblocks of various styrenic polymers have been synthesized by living carbocationic polymerization by sequential monomer addition. First isobutylene (IB) was polymerized by a bifunctional tert-ether (dicumyl methyl ether) initiator in conjunction with TiCl4 coinitiator in CH3Cl/methylcyclohexane (MeCHx) (40/60 v/v) solvent mixtures at -80°C. After the living narrow molecular weight distribution PIB midblock ($\[\bar M_n\]$ = 1.1-1.2) has reached the desired molecular weight, the styrenic monomers together with an electron pair donor (ED) and a proton trap (di-tert-butylpyridine, DtBP) were added to start the blocking of the glassy segments from the living ⊕PIB⊕ chain ends. While p-methylstyrene (pMeSt), p-t-butylstyrene (ptBuSt) and indene (In) gave essentially 100% blocking to the corresponding glassy endblocks, the blocking of 2,4,6-trimethylstyrene (TMeSt) and α-methylstyrene (αMeSt) were ineffective. Uncontrolled initiation by protic impurities was prevented by the use of DtBP. In the simultaneous presence of DtBP and the strong ED N,N-dimethylacetamide (DMA), TPEs with good mechanical properties (10-20 MPa tensile strength, 300-600% elongation) were prepared. The products exhibit a low and a high temperature Tg characteristic of phase separated rubbery and glassy domains. The service temperature of these new TPEs exceeds that of PSt-PIB-PSt triblock copolymers due to the higher Tgs (PpMeSt = 108, PptBuSt = 142 and PIn = 220-240°C) of the outer blocks. The Tg of the glassy blocks can be regulated by copolymerizing two styrene derivatives; a triblock copolymer with outer blocks of poly(pt-butylstyrene-co-indene) showed a single glassy transition Tg = +165°C, i.e., in between that of PptBuSt and PIn. Virgin TPEs have been repeatedly compression molded without deterioration of physical properties. The high melt flow index obtained with a TPE containing PptBuSt endblocks suggests superior processability relative to those with PSt end-blocks. The tensile strength retention at 60°C of the former TPE is far superior to that of a PSt-PIB-PSt triblock of similar composition.
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  • 4
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New linear and three-arm star thermoplastic elastomers (TPEs) comprising a rubbery polysobutylene (PIB) midblock flanked by glass polystyrene (PSt) blocks have been synthesized by living carbocationic polymerization in the presence of select additives by sequential monomer addition. First, isobutylene (IB) was polymerized by bi- and trifunctional tert-ether (dicumyl- and tricumyl methoxy) initiators in conjunction with TiCl4 conintiator in CH3Cl/methylcyclohexane (MeCHx) (40/60 v/v) solvent mixtures at -80°C. After the living, narrow molecular weight, distribution PIB (M̄w/M̄n = 1.1-1.2) has reached the desired molecular weight, styrene (St) together with an electron pair donor (ED) and a proton trap (di-tert-butylpyridine, DtBP) were added to block PSt from the living chain ends. Uncontrolled initiation by protic impurities that produces PSt contamination is prevented by the use of DtBP. PSt-PIB-PSt blocks obtained in the absence of additives are contaminated by homopolymer and /or diblocks due to inefficient blocking and initiation by protic impurities, and exhibit poor physical properties. In contrast in the presence of the strong ED N,N-dimethylacetamide (DMA) and DtBP the blocking of St from living PIB chain occurs efficiently and block copolymers exhibiting good mechanical properties can be prepared. Virgin TPEs can be repeatedly compression molded without deterioration of physical properties. The products exhibit a low and a high temperature Tg characteristic of phase separated PIB and PSt domains. Transmission electron microscopy of linear triblocks containing ∼ 34 wt % PSt also indicates microphase separation and suggests PSt rods dispersed in a PIB matrix.
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  • 5
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The living carbocationic polymerisation of styrene (St) has been investigated by the 2-chloro-2,4,4-trimethylpentane (TMPCI)/TiCl4 initiating system in the presence of various additives such as electron pair donors (EDs) and the proton trap 2,6-di-tert-butylpyridine (DtBP) by the use of the mixed solvent CH3Cl/methyl-cyclohexane (MCHx) (40/60 v/v) at -80°C under conventional laboratory conditions. The TMPCl/TiCl4 system in the absence of additives produces ill-defined bimodal molecular weight distribution (MWD) polymers. Much better defined polystyrenes (PSt) can be obtained in the presence of EDs, such as N,N-dimethylacetamide (DMA) and hexamethylphosphoramide (HMPA). Monomer depletion should be avoided to prevent intra- or intermolecular alkylation yielding indanyl end groups or branched polymers, respectively. In the combined presence of an ED and the proton trap, i.e., DMA + DtBP, the living polymerization of St has been achieved and thus the foundations for the carbocationic synthesis of PSt block polymers by sequential monomer addition have been laid.
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  • 6
    ISSN: 1573-1561
    Keywords: Spodoptera exigua ; Lepidoptera ; Noctuidae ; psoralen ; 5-methoxypsoralen ; 8-methoxypsoralen ; furanocoumarins ; antagonistic toxicity ; plant-insect interactions ; Apium prostratum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The linear furanocoumarins psoralen, bergapten, and xanthotoxin were tested for toxicity to the beet armywormSpodoptera exigua (Hübner) under short ultraviolet (UVB) radiation. Increased dietary concentrations of each furanocoumarin significantly decreased insect larval weight, extended generation time, and induced higher mortality. Xanthotoxin was the most toxic, followed by psoralen and bergapten. Combining psoralen with bergapten, xanthotoxin, or both resulted in significantly antagonistic effects on insect mortality. The combination of bergapten and xanthotoxin, however, produced additive effects. The implications of these observations forS. exigua resistance in the wild plant accession ofApium prostratum and the enigma the findings represent for plant-insect relationships are discussed.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 10 (1959), S. 74-77 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: High Temperature Corrosion in Petrol Refining by Sulfur CompoundsAt temperatures above 260°C only stainless, highly alloyed steels resist the attack of the most corrosive agent in petrol refining which is hydrogen sulfide. For high temperature corrosion by hydrogen sulfide, the influences of the duration of wear, the concentration of the hydrogen sulfide, the pressure, the properties of the refined petrol and the quality of the steel are of essential importance besides of the effects of temperature. The author reports on last years investigations in BP-research station on the corrosion of stainless steels by hydrogen sulfide at high temperatures. The corrosion of the surface, the inter-crystalline corrosion and the stress corrosion of steels are discussed in detail.
    Notes: Dem Angriff des wesentlichsten korrosiven Agens in Erdölraffinerien, dem Schwefelwasserstoff, bei hohen Temperaturen (über 260°C) widerstehen praktisch ausschließlich rostfreie, hochlegierte Stähle. Bei der Hochtemperatur-Korrosion durch Schwefelwasserstoff sind neben der Temperatur auch Beanspruchungsdauer, Schwefelwasserstoff konzentration, Druck, Beschaffenheit des zu raffinierenden Öles und die Stahlqualität von Einfluß. Verfasser berichtet über die in den letzten Jahren in der BP-Research Station durchgeführten Untersuchungen über die Korrosion von rostfreien Stählen durch Schwefelwasserstoff bei hohen Temperaturen, wobei allgemeine Oberflächen-korrosion, interkristalline Korrosion und Spannungskorrosion der Stähle eingebend behandelt werden.
    Additional Material: 11 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 931-942 
    ISSN: 0887-6266
    Keywords: nuclear magnetic resonance (NMR) relaxation in polymer melts ; relaxation of proton NMR processes in melts (theory) ; chain motions and NMR relaxation in melts ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A theoretical treatment of the nonexponential relaxation behavior of the different proton nuclear magnetic resonance (NMR) relaxation processes in polymer melts is presented. Formulas are derived for a three-component model given by two versions and a homogeneous distribution of correlation times. The theoretical results were tested with measurements of T1, T2e, and T2 as functions of frequency and molecular mass in linear fractionated polyethylene samples. While the T1 relaxation always yields exponential magnetization decays, the T2e and T2 measurements show biexponential relaxation behavior. From the calculations it was found that the correlation time of the local motion is independent of the molecular mass, whereas the correlation time of the slowest motional process increases with M2.8w for the three-component model and with M2.2w for the distribution of correlation times, respectively. © 1992 John Wiley & Sons, Inc.
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  • 9
    ISSN: 0887-6266
    Keywords: miscibility of polycarbonate blends ; domain size of acrylic and polycarbonate blends ; imaging analysis ; intramolecular interactions in copolymer ; 1H T1p (proton NMR relaxation time) ; Differential Scanning Calorimetry ; Transmission Electron Microscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The miscibility of polycarbonate (PC) with poly(methyl methacrylate-co-cyclohexyl methacrylate) (PMCHM) and with poly(methyl methacrylate) (PMMA) was studied by nuclear magnetic resonance (NMR) 1H spin-lattice relaxation time in the rotating frame (1H T1p), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). A blend of PC/PMCHM (50/50 wt/wt) with the acrylic component PMCHM, a copolymer of PMMA and poly(cyclohexyl methacrylate) (80/20 wt/wt), shows only one T1p value, which indicates high miscibility in this blend. A blend of PC/PMMA (50/50 wt/wt) shows two 1H T1p values, which are similar to those of the homopolymers PC and PMMA. These results indicate high immiscibility. The “domain size” calculated from NMR results of the miscible blend PC/PMCHM is approximately 40 Å. The results of DSC and TEM are similar to the NMR results. However, TEM results show the presence of 3% PC domains in the PC/PMCHM blend, which are not seen by NMR or DSC. Those PC domains are approximately 500 Å. A strong intramolecular repulsion in the copolymer PMCHM and specific intermolecular interactions between PC and PMMA may explain the miscibility in the PC/PMCHM system. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 329-349 
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: The rheological and morphological properties of several melt-blended compositions of poly(ethylene terephthalate) (PET) and Vectra A900 liquid crystalline polyester were investigated, using blending temperature, composition, and shear rate as variables. Rheological behavior was determined at several shear rates on an Instron capillary rheometer at 300°C, and three-dimensional surface plots of the results were prepared, detailing the effect on melt viscosity of changes in the variables. Scanning electron microscopy was used to examine the internal morphology of selected samples. In the preparation of melt blends containing an isotropic and anisotropic polymer, blending temperature and composition both influence the resulting morphology. These effects are accentuated during extrusion of the blends at low shear rates and diminished at high shear rates.
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