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Specific Properties (specific + property)
Selected AbstractsLiving cationic polymerization of amide-functional vinyl ethers: Specific properties of SnCl4 -based initiating systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2008Motomasa Yonezumi Abstract Living cationic copolymerization of amide-functional vinyl ethers with isobutyl vinyl ether (IBVE) was achieved using SnCl4 in the presence of ethyl acetate at 0 °C: the number,average molecular weight of the obtained polymers increased in direct proportion to the monomer conversion with relatively low polydispersity, and the amide-functional monomer units were introduced almost quantitatively. To optimize the reaction conditions, cationic polymerization of IBVE in the presence of amide compounds, as a model reaction, was also examined using various Lewis acids in dichloromethane. The combination of SnCl4 and ethyl acetate induced living cationic polymerization of IBVE at 0 °C when an amide compound, whose nitrogen is adjacent to a phenyl group, was used. The versatile performance of SnCl4 especially for achieving living cationic polymerization of various polar functional monomers was demonstrated in this study as well as in our previous studies. Thus, the specific properties of the SnCl4 initiating system are discussed by comparing with the EtxAlCl3,x systems from viewpoints of hard and soft acids and bases principle and computational chemistry. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6129,6141, 2008 [source] Differential modulation of AMPA receptors by cyclothiazide in two types of striatal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2000Vladimir S. Vorobjev Abstract The modulation of ,-amino-3-hydroxy-5-methyl-4-isoxazol-propionate (AMPA) receptor-mediated currents by cyclothiazide was investigated in acutely isolated cells from rat striatum with whole-cell patch-clamp recording. Single-cell reverse transcriptase-polymerase chain reaction (RT-PCR) was used to identify medium spiny and giant aspiny neurons and to determine their AMPA receptor subunit composition mostly in separate experiments. After pretreatment with cyclothiazide, kainate-induced AMPA responses were more strongly potentiated in medium spiny than in giant aspiny neurons; cyclothiazide induced a ninefold leftward shift in the kainate concentration,response curve for medium spiny neurons (not giant aspiny neurons). The EC50s for the cyclothiazide potentiation did not differ substantially between medium spiny neurons and giant aspiny neurons. The recovery of kainate-activated currents from modulation by cyclothiazide was slower for medium spiny neurons than for giant aspiny neurons. Medium spiny neurons expressed GluR-A, GluR-B and GluR-C, but not GluR-D subunits in both flip and flop splice variants. All giant aspiny neurons expressed GluR-A and GluR-D, exclusively in the flop form, half of them also expressed GluR-B and GluR-C. This is in keeping with slow and fast desensitization kinetics in medium spiny neurons and giant aspiny neurons, respectively, and differences in cyclothiazide modulation. The rate of cyclothiazide dissociation from the AMPA receptor, activated by glutamate, was ,,90 times slower in medium spiny neurons than in giant aspiny neurons. In giant aspiny neurons (not medium spiny neurons) this rate was strongly dependent on the presence of an agonist; 1 m m glutamate increased it 30-fold. Thus, two major cell groups in the striatum display distinct AMPA receptor compositions carrying specific properties of glutamate responses. Excitatory transmission will thus be differentially affected by cyclothiazide-type compounds. [source] Facts, fantasies and fun in epithelial physiologyEXPERIMENTAL PHYSIOLOGY, Issue 3 2008C. A. R. Boyd The hallmark of epithelial cells is their functional polarization. It is those membrane proteins that are distributed differentially, either to the apical or to the basal surface, that determine epithelial physiology. Such proteins will include ,pumps', ,channels' and ,carriers', and it is the functional interplay between the actions of these molecules that allows the specific properties of the epithelium to emerge. Epithelial properties will additionally depend on: (a) the extent to which there may be a route between adjacent cells (the ,paracellular' route); and (b) the folding of the epithelium (as, for example, in the loop of Henle). As for other transporters, there is polarized distribution of amino-acid carriers; the molecular basis of these is of considerable current interest with regard to function, including ,inborn errors' (amino-acidurias); some of these transporters have additional functions, such as in the regulation of cell fusion, in modulating cell adherence and in activating intracellular signalling pathways. Collaboration of physiologists with fly geneticists has generated new insights into epithelial function. One example is the finding that certain amino-acid transporters may act as ,transceptors' and play a role as sensors of the extracellular environment that then regulate intracellular pathways controlling cell growth. [source] The porcine trophoblastic interferon-,, secreted by a polarized epithelium, has specific structural and biochemical propertiesFEBS JOURNAL, Issue 11 2002Avrelija Cenci At the time of implantation in the maternal uterus, the trophectoderm of the pig blastocyst is the source of a massive secretion of interferon-gamma (IFN-,), together with lesser amounts of IFN-,, a unique species of type I IFN. This trophoblastic IFN-, (TrIFN-,) is an unprecedented example of IFN-, being produced spontaneously by an epithelium. We therefore studied some of its structural and biochemical properties, by comparison with pig IFN-, from other sources, either natural LeIFN-, (from adult leucocytes), or recombinant. Biologically active TrIFN-, is a dimeric molecule, of which monomers are mainly composed of a truncated polypeptide chain with two glycotypes, unlike LeIFN-, which is formed of at least two polypeptide chains and four glycotypes. TrIFN-, collected in the uterus lumen was enzymatically deglycosylated and analysed by mass spectrometry (MALDI-TOF). The data revealed that the more abundant polypeptide has a mass of 14.74 kDa, corresponding to a C-terminal cleavage of 17 residues from the expected 143-residue long mature sequence. A minor polypeptide, with a mass of 12.63 kDa, corresponds to a C-terminal truncation of 36 amino acids. MALDI-TOF analysis of tryptic peptides from the glycosylated molecule(s) identifies a single branched carbohydrate motif, with six N -acetylgalactosamines, and no sialic acid. The only glycan microheterogeneity seems to reside in the number of l -fucose residues (one to three). The lack of the C-terminal cluster of basic residues, and the presence of nonsialylated glycans, result in a very low net charge of TrIFN-, molecule. However, the 17-residue truncation does not affect the antiproliferative activity of TrIFN-, on different cells, among which is a porcine uterine epithelial cell line. It is suggested that these specific properties might confer on TrIFN-, a particular ability to invade the uterine mucosa and exert biological functions beyond the endometrial epithelium. [source] The Combined Effects of Immersion and Instruction on Second Language PronunciationFOREIGN LANGUAGE ANNALS, Issue 3 2010Gillian Lord Abstract: This preliminary study investigates the acquisition of second language phonology with respect to two variables: immersion in a target language community, and explicit instruction in the form of a phonetics/pronunciation class. Specifically, the research examines the second language acquisition (SLA) of specific properties of the Spanish phonology system as achieved by native speakers of English participating in a summer program in Mexico, some of whom had previously taken a Spanish phonetics course. Results suggest that it is not one factor or another in isolation that is most beneficial, but rather the combination of the two. The findings are analyzed not only in terms of how the SLA of sound systems develops, but also with respect to pedagogical, curricular, and administrative implications. [source] Pumping-Induced Drawdown and Stream Depletion in a Leaky Aquifer SystemGROUND WATER, Issue 2 2007James J. Butler Jr The impact of ground water pumping on nearby streams is often estimated using analytic models of the interconnected stream-aquifer system. A common assumption of these models is that the pumped aquifer is underlain by an impermeable formation. A new semianalytic solution for drawdown and stream depletion has been developed that does not require this assumption. This solution shows that pumping-induced flow (leakage) through an underlying aquitard can be an important recharge mechanism in many stream-aquifer systems. The relative importance of this source of recharge increases with the distance between the pumping well and the stream. The distance at which leakage becomes the primary component of the pumping-induced recharge depends on the specific properties of the aquifer, aquitard, and streambed. Even when the aquitard is orders of magnitude less transmissive than the aquifer, leakage can be an important recharge mechanism because of the large surface area over which it occurs. Failure to consider aquitard leakage can lead to large overestimations of both the drawdown produced by pumping and the contribution of stream depletion to the pumping-induced recharge. The ramifications for water resources management and water rights adjudication can be significant. A hypothetical example helps illustrate these points and demonstrates that more attention should be given to estimating the properties of aquitards underlying stream-aquifer systems. The solution presented here should serve as a relatively simple but versatile tool for practical assessments of pumping-induced stream-aquifer interactions. However, this solution should not be used for such assessments without site-specific data that indicate pumping has induced leakage through the aquitard. [source] Nanomaterials for Neural InterfacesADVANCED MATERIALS, Issue 40 2009Nicholas A. Kotov Abstract This review focuses on the application of nanomaterials for neural interfacing. The junction between nanotechnology and neural tissues can be particularly worthy of scientific attention for several reasons: (i) Neural cells are electroactive, and the electronic properties of nanostructures can be tailored to match the charge transport requirements of electrical cellular interfacing. (ii) The unique mechanical and chemical properties of nanomaterials are critical for integration with neural tissue as long-term implants. (iii) Solutions to many critical problems in neural biology/medicine are limited by the availability of specialized materials. (iv) Neuronal stimulation is needed for a variety of common and severe health problems. This confluence of need, accumulated expertise, and potential impact on the well-being of people suggests the potential of nanomaterials to revolutionize the field of neural interfacing. In this review, we begin with foundational topics, such as the current status of neural electrode (NE) technology, the key challenges facing the practical utilization of NEs, and the potential advantages of nanostructures as components of chronic implants. After that the detailed account of toxicology and biocompatibility of nanomaterials in respect to neural tissues is given. Next, we cover a variety of specific applications of nanoengineered devices, including drug delivery, imaging, topographic patterning, electrode design, nanoscale transistors for high-resolution neural interfacing, and photoactivated interfaces. We also critically evaluate the specific properties of particular nanomaterials,including nanoparticles, nanowires, and carbon nanotubes,that can be taken advantage of in neuroprosthetic devices. The most promising future areas of research and practical device engineering are discussed as a conclusion to the review. [source] Type of Maternal Object Motion During Synchronous Naming Predicts Preverbal Infants' Learning of Word,Object RelationsINFANCY, Issue 2 2008Dalit J. Matatyaho Mothers' use of specific types of object motion in synchrony with object naming was examined, along with infants' joint attention to the mother and object, as a predictor of word learning. During a semistructured 3-min play episode, mothers (N = 24) taught the names of 2 toy objects to their preverbal 6- to 8-month-old infants. The episodes were recoded from Gogate, Bolzani, and Betancourt (2006) to provide a more fine-grained description of object motions used by mothers during naming. The results indicated that mothers used forward/downward and shaking motions more frequently and upward and backward motions less frequently in temporal synchrony with the spoken words. These motions likely highlight novel word,object relations. Furthermore, maternal use of shaking motions in synchrony with the spoken words and infants' ability to switch gaze from mother to object contributed to infants' learning of the word,object relations, as observed on a posttest. Thus, preverbal infants' learn word,object relations within an embodied system involving tightly coupled interaction between infants' perception and joint attention, and specific properties of caregivers' naming. [source] Awakening dynamics via passive coupling and synchronization mechanism in oscillatory cellular neural/nonlinear networksINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 5-6 2008István Szatmári Abstract We have studied synchronization mechanism in locally coupled nonlinear oscillators. Here, synchronization takes place by passive coupling based on a reaction,diffusion process. We will compare this mechanism with basic synchronization techniques, showing their similarities and specific properties. In addition to synchronization, passive and local coupling can also ,awaken' non-oscillating cell circuits and trigger oscillation, provided that cells are locally active. This result resembles Turing's and Smale's works showing that locally communicating simple elements can produce very different patterns even if separate elements do not show any activity. This property will be demonstrated for two second-order cells and also for a large ensemble of oscillatory cells. In latter case, the network of oscillatory cells exhibits very sophisticated spatio-temporal waves, e.g. spiral waves. Copyright © 2008 John Wiley & Sons, Ltd. [source] An Interactive Reference Direction Algorithm For Solving Multi-Objective Convex Nonlinear Integer Programming ProblemsINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 4 2001Vassil S. Vassilev We present a learning-oriented interactive reference direction algorithm for solving multi-objective convex nonlinear integer programming problems. At each iteration the decision-maker (DM) sets his/her preferences as aspiration levels of the objective functions. The modified aspiration point and the solution found at the previous iteration define the reference direction. Based on the reference direction, we formulate a mixed-integer scalarizing problem with specific properties. By solving this problem approximately, we find one or more integer solutions located close to the efficient surface. At some iteration (usually at the last iteration), the DM may want to solve the scalarizing problem to obtain an exact (weak) efficient solution. Based on the proposed algorithm, we have developed a research-decision support system that includes one exact and one heuristic algorithm. Using this system, we illustrate the proposed algorithm with an example, and report some computational results. [source] Disease Status in Autosomal Dominant Osteopetrosis Type 2 Is Determined by Osteoclastic Properties,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2006Kang Chu Abstract Asymptomatic gene carriers and clinically affected ADO2 subjects have the same ClCN7 mutation. We examined osteoclastic bone resorption in vitro as well as osteoclast formation, several markers, acid secretion, and cytoskeletal structure. We found that ADO2 expression results from osteoclast specific properties. Introduction: Autosomal dominant osteopetrosis type II (ADO2) is a heritable osteosclerotic disorder that results from heterozygous mutations in the ClCN7 gene. However, of those individuals with a ClCN7 mutation, one third are asymptomatic gene carriers who have no clinical, biochemical, or radiological manifestations. Disease severity in the remaining two thirds is highly variable. Materials and Methods: Human peripheral blood mononuclear cells were isolated and differentiated into osteoclasts by stimulation with hRANKL and human macrophage-colony stimulating factor (hM-CSF). Study subjects were clinically affected subjects, unaffected gene carriers, and normal controls (n = 6 in each group). Pit formation, TRACP staining, RANKL dose response, osteoclast markers, acid secretion, F-actin ring, and integrin ,v,3 expression and co-localization were studied. Results: Osteoclasts from clinically affected subjects had severely attenuated bone resorption compared with those from normal controls. However, osteoclasts from unaffected gene carriers displayed similar bone resorption to those from normal controls. In addition, the resorption lacunae from both unaffected gene carriers and normal controls appeared much earlier and spread much more rapidly than those from clinically affected subjects. As time progressed, the distinction between clinically affected subjects and the other two groups increased. No significant difference was found in acidic secretion or osteoclast formation between the three groups. Osteoclast cytoskeletal organization showed no difference between the three groups but there was low cellular motility in clinically affected subjects. Conclusions: Osteoclasts from the unaffected gene carriers, in contrast to those from the clinically affected subjects, functioned normally in cell culture. This finding supports the hypothesis that intrinsic osteoclast factors determine disease expression in ADO2. Further understanding of this mechanism is likely to lead to the development of new approaches to the treatment of clinically affected patients. [source] Supercritical water for environmental technologiesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2010Dr Anne Loppinet-Serani Abstract OVERVIEW: Supercritical water is a great medium in which to perform chemical reactions and to develop processes. Due to its unique thermo-physico-chemical properties, supercritical water is able to play the role of solvent of organic compounds and/or to react with them. These specific properties have been used since the 1990s to develop new technologies dedicated to the environment and energy. IMPACT: Supercritical water based technologies are innovative and efficient processes having a strong impact on society, the environment and the economy, and is termed a sustainable technology. APPLICATIONS: Three main applications for supercritical water technology are under development: (i) supercritical water oxidation (SCWO); (ii) supercritical water biomass gasification (SCBG); and (iii) hydrolysis of polymers in supercritical water (HPSCW) for composites/plastics recycling. In this paper some fundamentals of supercritical water are first presented to introduce the above three major developments. Then these technologies are reviewed in terms of their present and future industrial development and their impact on the environment and on energy production. Copyright © 2010 Society of Chemical Industry [source] Properties and applications of supports for enzyme-mediated transformations in solid phase synthesisJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2006Alessandra Basso Abstract With the increasing interest in automated synthesis and screening protocols, solid supported chemistry and biochemistry have become attractive technologies. Furthermore, the use of enzymes in solid phase synthesis has opened the route to selective and mild processes. The efficiency of enzymes in transforming substrates that are bound on solid supports is strictly related to the availability of polymers endowed with specific properties, above all permeability to enzymes. This review describes how the recent developments of this rapidly evolving area have made possible novel challenging applications of enzymes in solid phase synthesis. Copyright © 2006 Society of Chemical Industry [source] Nutshells as granular activated carbons: physical, chemical and adsorptive properties,JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2001H Wartelle Abstract Nutshells from seven different sources (pistachio, hazelnut, almond, black walnut, English walnut, macadamia nut, pecan) were converted to granular activated carbons (GACs) by carbon dioxide activation. A portion of the GACs were oxidized with compressed air and the physical (yield, surface area, attrition), chemical (pH, surface charge) and adsorptive (organics uptake, metal ion uptake) properties of both oxidized and non-oxidized carbons were determined. Differences in uptake of organics, especially of polar compounds, were found between GACs made from almond shells, the group consisting of black walnut shells, English walnut shells and pecan shells, and macadamia nutshells. Oxidation had its greatest effects on pH, surface charge and uptake of metal ions. The changes due to oxidation were found to be independent of carbon source material. GACs with specific properties can be produced with judicious selection of carbon precursor and oxidative treatment. © 2001 Society of Chemical Industry [source] Absence of a specific subgingival microflora in adults with Down's syndromeJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 11 2001W. Reuland-Bosma Abstract Background: Periodontal disease in Down's syndrome (DS) is generally characterized by a high degree of bone loss. Bone loss of 5 mm or more is observed in 70% of these subjects. Among DS subjects, considerable differences in disease progression occur. So far, no studies have been conducted in which specific properties of the subgingival microflora have been related to the condition observed. Aims: To investigate (1) the subgingival microflora in DS subjects and other mentally retarded (control) individuals which were matched to the utmost and (2) to investigate the subgingival microflora of a "low-risk" and a " high-risk" group formed in DS subjects. Material and Methods: 17 DS subjects and 17 control subjects were matched with respect to age, plaque level and bleeding on probing. In addition, the DS group was divided in a "low-risk" group (0,2 teeth lost due to periodontal disease n=6) and a "high-risk"group (6,13 teeth lost due to periodontal disease n=11). Prevalence and proportions of the putative periodontal pathogens Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Bacteroides forsythus, Peptostreptococcus micros, Fusobacterium nucleatum and Campylobacter rectus in the subgingival plaque were determined using anaerobic culture techniques. No differences in the prevalence of distinct suspected periodontopathic bacteria and bacterial subgingival composition between the DS group and the control group could be established. Also no differences in the prevalence of the seven investigated microbial species between the "low-risk" and the "high-risk" group were observed. Conclusions: Because of the lack of differences in microflora between the DS group and the control group, a specific effect of the microbiological composition in the periodontal status of subjects with DS can be excluded in this population. Host factors constitute the more likely explanation of the differences observed in DS. Zusammenfassung Basis: Die parodontale Erkrankung beim Down Syndrom (DS) ist allgemein durch einen hohen Grad von Knochenverlust charakterisiert. Knochenverlust von 5 mm und mehr wird bei 70% der Personen beobachtet. Unter den DS Personen bestehen beträchtliche Differenzen in der Erkrankungsprogression. Bis heute sind keine Studien durchgeführt worden, in welchen die spezifischen Eingenschaften der subgingivalen Mikroflora in Beziehung zu den Bedingungen beobachtet wurden. Ziele: Untersuchung (1) der subgingivalen Mikroflora bei DS Personen und anderen mental retardierten (Kontrollen) Personen, die zu einer größten gemischt wurden und (2) der subgingivalen Mikroflora von Gruppen mit "geringem Risiko" und Gruppen mit "hohem Risiko" bei DS Personen. Material und Methoden: 17 DS Personen mit 17 Kontrollpersonen wurden im Hinblick auf Alter, Plaquemenge und Blutung auf Provokation eingeteilt. Zusätzlich wurde die DS Gruppe in "geringes Risiko" (0,2 Zähne infolge von parodontaler Erkrankung verloren, n=6) und in "hohes Risiko" (6,13 Zähne infolge parodontaler Erkrankung verloren, n=11) eingeteilt. Das Vorkommen und die Relationen von putativen parodontalen Pathogenen Actinobacillus actinomycetemcomitants, Porphyromonas gingivalis, Prevotella intermedia, Bacteroides forsythus, Peptostreptococcus micros, Fusobacterium nucleatum und Campylobacter rectus in der subgingivalen Plaque wurden mit anaerober Kulturtechnik bestimmt. Ergebnisse: Es konnten keine Differenzen in der Prävalenz der bezeichneten parodontopathogenen Bakterien und der bakteriellen subgingivalen Zusammensetzung zwischen DS Gruppe und der Kontrollgruppe beobachtet werden. Auch zwischen der Gruppe "geringes Risiko" und "hohes Risiko" wurden keine Differenzen in der Prävalenz der 7 untersuchten Spezies beobachtet. Schlußfolgerungen: Weil keine Differenzen in der Mikroflora zwischen DS Gruppe und der Kontrollgruppe vorhanden sind, kann ein spezifischer Effekt der mikrobiologischen Zusammensetzung beim parodontalen Status der Personen mit DS in dieser Population ausgeschlossen werden. Für die Erklärung der Differenzen, die bei den DS Personen beobachtet werden, sind die Wirtsfaktoren mehr wahrscheinlich. Résumé Origine: La maladie parodontale lors du syndrôme de Down (DS) est généralement caractérisée par une importante perte osseuse. Cette perte osseuse atteint 5 mm ou plus chez 70% de ces malades. Parmi les sujets DS, des différences considérables dans la progression de cette maladie se manifestent. Aucune étude n'a encore été entreprise dans laquelle la microflore sous-gingivale a été mise en relation avec les conditions observées. But: Le but de cette étude a été (1) d'analyser la microflore sous-gingivale chez les sujets DS et d'autres retardés mentaux servant de contrôles et (2) mieux connaître la microflore sous-gingivale chez les groupes de patients DS avec faible et haut risques. Matériaux et méthodes: 17 sujets DS et 17 sujets contrôles ont été analysés de manière parallèle en fonction de l'âge, du niveau de plaque dentaire et du saignement au sondage. De plus, le groupe DS était scindé en deux sous-groupes: "petit risque" (0 à 2 dents perdues pour cause de maladie parodontale; n=6), et "haut risque" (6 à 13 dents perdues; n=11). La fréquence globale et les proportions de pathogènes parodontaux putatifs l'Actinobacillus actinomycetemcomitans, le Porphyromonas gingivalis, le Prevotella intermedia, le Bacteroides forsythus, le Peptostreptococcus micros, le Fusobacterium nucleatum et le Campylobacter rectus dans la plaque sous-gingivale ont été déterminés en utilisant des techniques de culture anaérobie. Résultats: Aucune différence dans la fréquence globlale de ces bactéries ni dans la composition de la flore sous-gingivale n'a été trouvée entre le groupe DS et le groupe contrôle. Il n'y avait également aucune différence entre les sous-groupes à faible et à haut risques. Conclusions: Parce qu'aucune différence n'a été décelée dans la microflore entre les groupes DS et contrôle, aucun effet spécifique de leur flore sous-gingivale ne pourrait être responsable; les facteurs de l'hôte constituent très vraisemblablement l'explication des différences observées chez les sujets DS. [source] Synthesis of carbon-14 labeled [1- 14C]-, and [2- 14C]- L -tyrosineJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 8 2001W. Augustyniak Abstract Two labeled isotopomers of L -tyrosine, L -Tyr, have been synthesized using specific properties of the enzymes phenylanine ammonia lyase, PAL, and L -phenylalanine hydroxylase. In an intermediate step [1- 14C]-, and [2- 14C]- L -phenylalanine, L -Phe, have been obtained from [1- 14C]-, and [2- 14C]cinnamic acid, prepared from potassium [14C]cyanate or [2- 14C]malonic acid, and by addition of ammonia in the presence of enzyme PAL. The labeled isotopomers of L -Phe have been converted into [1- 14C]-, and [2- 14C]- L -Tyr using the enzyme L -phenylalanine hydroxylase. Copyright © 2001 John Wiley & Sons, Ltd. [source] Three-dimensional analysis of intermediate filament networks using SEM tomographyJOURNAL OF MICROSCOPY, Issue 1 2010S. LÜCK Summary We identified tomographic reconstruction of a scanning electron microscopy tilt series recording the secondary electron signal as a well-suited method to generate high-contrast three-dimensional data of intermediate filament (IF) networks in pancreatic cancer cells. Although the tilt series does not strictly conform to the projection requirement of tomographic reconstruction, this approach is possible due to specific properties of the detergent-extracted samples. We introduce an algorithm to extract the graph structure of the IF networks from the tomograms based on image analysis tools. This allows a high-resolution analysis of network morphology, which is known to control the mechanical response of the cells to large-scale deformations. Statistical analysis of the extracted network graphs is used to investigate principles of structural network organization which can be linked to the regulation of cell elasticity. [source] Physical characterization of component particles included in dry powder inhalers.JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2007Abstract Characteristics of particles included in dry powder inhalers is extended from our previous report (in this journal) to include properties related to their dynamic performance. The performance of dry powder aerosols for pulmonary delivery is known to depend on fluidization and dispersion which reflects particle interactions in static powder beds. Since the solid state, surface/interfacial chemistry and static bulk properties were assessed previously, it remains to describe dynamic performance with a view to interpreting the integrated database. These studies result in complex data matrices from which correlations between specific properties and performance may be deduced. Lactose particles were characterized in terms of their dynamic flow, powder and aerosol electrostatics, and aerodynamic performance with respect to albuterol aerosol dispersion. There were clear correlations between flow properties and aerosol dispersion that would allow selection of lactose particles for formulation. Moreover, these properties can be related to data reported earlier on the morphological and surface properties of the carrier lactose particles. The proposed series of analytical approaches to the evaluation of powders for inclusion in aerosol products has merit and may be the basis for screening and ultimately predicting particle performance with a view to formulation optimization. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 1302,1319, 2007 [source] Living cationic polymerization of amide-functional vinyl ethers: Specific properties of SnCl4 -based initiating systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2008Motomasa Yonezumi Abstract Living cationic copolymerization of amide-functional vinyl ethers with isobutyl vinyl ether (IBVE) was achieved using SnCl4 in the presence of ethyl acetate at 0 °C: the number,average molecular weight of the obtained polymers increased in direct proportion to the monomer conversion with relatively low polydispersity, and the amide-functional monomer units were introduced almost quantitatively. To optimize the reaction conditions, cationic polymerization of IBVE in the presence of amide compounds, as a model reaction, was also examined using various Lewis acids in dichloromethane. The combination of SnCl4 and ethyl acetate induced living cationic polymerization of IBVE at 0 °C when an amide compound, whose nitrogen is adjacent to a phenyl group, was used. The versatile performance of SnCl4 especially for achieving living cationic polymerization of various polar functional monomers was demonstrated in this study as well as in our previous studies. Thus, the specific properties of the SnCl4 initiating system are discussed by comparing with the EtxAlCl3,x systems from viewpoints of hard and soft acids and bases principle and computational chemistry. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6129,6141, 2008 [source] Multisensitive polymers based on 2-vinylpyridine and N -isopropylacrylamide ,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2001Sebastian Wohlrab Abstract Poly(2-vinylpyridine) (P2VP) containing functionalized end groups was synthesized using nitroxyl-mediated radical polymerization with a hydroxy-functionalized stable free radical. It was shown that P2VP could be synthesized with variable molar masses and low polydispersities. The transformation of the hydroxy groups to an acrylic ester led to the formation of macromonomers. A free-radical copolymerization of these macromonomers with N -isopropylacrylamide gave a graft copolymer with a poly(N -ispopropylacrylamide) backbone and P2VP side chains. Polymers containing different amounts of the monomers were synthesized. It was possible to vary both the amount of P2VP side chains at a constant chain length of the macromonomer and the chain length at a nearly constant chain number. The behavior of the multifunctional macromolecules at different temperatures and pH values was investigated using dynamic light scattering and DSC. The macromolecules were found to retain the specific properties of the homopolymers. The hydrodynamic radii of the synthesized graft copolymers were both dependent on the temperature and pH value. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3797,3804, 2001 [source] Liposomes in dermatology todayJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 5 2009J De Leeuw Abstract Liposomes are vesicles consisting of spherical phospholipid bi-layers with specific properties making them useful for topical application of drugs. Liposome research has expanded considerably over the last 30 years and nowadays, it is possible to construct a wide range of liposomes varying in size, phospholipids composition and surface characteristics to suit the specific application for which they are intended. In dermatology, the topical application of liposomes has proven to be of therapeutic value. Liposomes can be used as carriers for hydrophilic as well as lipophilic therapeutic agents because of their amphipathic character. They may improve stabilization of instable drugs by encapsulating them and serve as penetration enhancers facilitating the transport of compounds that otherwise cannot penetrate the skin. Liposomes help in reducing skin irritation by sustaining the release of drugs and by hydration of the epidermis. They also have the potential to target drugs into the pilosebaceous structures and hence they have an additional advantage for treatment of hair follicle-associated disorders. Clinical data indicate that 5-ALA encapsulated in liposomes improves the quality of Fluorescence Diagnosis by ALA-induced Porphyrins (FD) and optimizes the results of Photodynamic Therapy (PDT). Conflicts of interest None declared [source] Entwicklung hochverschleißbeständiger wolframschmelzkarbidbasierter Schichten auf Aluminiumbauteilen durch Plasma-Pulver-Auftragschweißen,MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 7 2007S. Kondapalli Dipl.-Ing. plasma transferred arc welding; wear-resistant coating; aluminium; composite coating; fused tungsten carbide Abstract Durch den Einsatz von Wolframschmelzkarbid können Funktionsflächen von Bauteilen mit stark abrasiven Beanspruchungen wirkungsvoll geschützt werden. Bereits seit vielen Jahren wird Wolframschmelzkarbid eingesetzt, um die Verschleißeigenschaften von Stahl zu verbessern. In diesem Artikel werden Ergebnisse von Untersuchungen zum Verschleißschutz von Aluminiumoberflächen mithilfe des Plasma-Pulver-Auftragschweißens von wolframschmelzkarbidbasierten Schichten vorgestellt. Die Wolframschmelzkarbid-Schichten werden mit zwei Methoden entwickelt, zum einen durch Dispergieren von Wolframschmelzkarbidpartikeln, zum anderen durch eine Kombination aus Dispergieren und Legieren von Verbundpulvern auf Wolframschmelzkarbidbasis. Die Schweißbarkeit der Pulversysteme wird für variierende Auftragschweißparameter und Karbidpartikelanteile untersucht. Im Anschluss erfolgt die Analyse der spezifischen Eigenschaften und der Verschleißbeständigkeit der entwickelten Schichten. Abschließend wird das Anwendungspotenzial am Beispiel von Führungsrollen dargestellt. Development of high wear-resistant FTC-based coatings on aluminium components using plasma transferred arc welding Nowadays, functional surfaces of components can be effectively protected from extreme wear with the help of fused tungsten carbide (FTC) coatings. The wear protection of steel components using FTC has been well known for many years. This paper presents the feasible study of improving the wear resistance of aluminium components with FTC particles using plasma powder arc welding. The FTC coatings are developed with two methods: one is the dispersion of carbide particles in aluminium and the other one is the combination of dispersing and alloying of FTC-based composite powders. In this research, coatings within a thickness range of a few millimeters are developed with varying process parameters and compositions of the filler materials. The developed coating systems are tested with regard to their specific properties and their wear resistance. Finally, their application potential is presented. [source] Herstellung verbundverstärkter Aluminiumprofile für ultraleichte Tragwerke durch StrangpressenMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 7 2004M. Kleiner Extrusion; Aluminum; Continuously Reinforcement; Special Tool Abstract Auf Grund ähnlicher spezifischer Steifigkeits- und Festigkeitseigenschaften von Aluminium und Stahl lassen sich in der Anwendung bei leichten Rahmenstrukturen durch gegenseitige Werkstoffsubstitution nur geringe Leichtbaugewinne erzielen. Lediglich die Verwendung von z.,B. Kohlefaserwerkstoffen oder Höchstleistungsstählen lässt eine Gewichtsreduktion für den Einsatz von Rohren oder Profilen in ultraleichten Strukturen erwarten. Am Lehrstuhl für Umformtechnik (LFU) der Universität Dortmund ist ein Verfahren entwickelt worden, das durch ein modifiziertes Strangpressen zur Herstellung von Verbundprofilen geeignet ist. Ausgehend von konventionellen Aluminium-Pressblöcken werden hierbei verschiedenartige endlose Verstärkungselemente innerhalb der Wandstärke der Profilmatrix eingebettet. Für das Verfahren, das im Rahmen des Sonderforschungsbereiches SFB/TR10 erforscht wird, ist die Entwicklung neuartiger Strangpresswerkzeuge erforderlich. Durch experimentelle Untersuchungen auf einer 2,5 MN Laborstrangpresse wurden erfolgreich erste Verbundprofile hergestellt. Zur Vertiefung des Prozessverständnisses und der Prognose der Wirksamkeit neuer Werkzeugkonzepte wurden parallel FEM-Simulationen durchgeführt. Die mit Hilfe des Verfahrens hergestellten geraden Verbundprofile lassen sich auf Grund möglicher Gefügeschädigungen nicht biegen. In Kombination mit dem ebenfalls am LFU entwickelten Verfahren Runden beim Strangpressen werden diese Verbundprofile jedoch auch mit gekrümmter Kontur herstellbar sein. Manufacture of Extruded and Continuously Reinforced Aluminum Profiles for Ultra-Lightweight Constructions Due to similar specific properties of aluminum and steel regarding stiffness and mechanical strength only minor achievements as to their application in lightweight space-frame structures can be attained by substituting one material for the other. Only the usage of carbon fibre materials or high performance steels promises a weight reduction as to the application of pipes and profiles in ultra-lightweight structures. At the Chair of Forming Technology of the University of Dortmund a process has been developed which is suitable for the manufacturing of continuously reinforced profiles by means of a modified direct extrusion process. Starting from conventional aluminum billets, various continuously reinforcing elements are being embedded in the wall thickness of the profile matrix. For this process, which is being investigated in the context of the Collaborative Research Centre SFB/TR10, new extrusion dies have to be developed. During experimental studies on a 2.5 MN laboratory direct extrusion press first reinforced profiles were manufactured successfully. In order to improve the understanding of the process and to predict the efficiency of new tool concepts, FEM simulations were carried out simultaneously. Reinforced straight profiles produced with the help of this method cannot be bend due to possible damages to the microstructure. However, in combination with the process of Rounding During Extrusion, which also has been developed at the Chair of Forming Technology, these reinforced profiles will be producible with a curved contour as well. [source] Ultraluminous X-ray sources and star formationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2004A. R. King ABSTRACT Chandra observations of the Cartwheel galaxy reveal a population of ultraluminous X-ray sources (ULXs) with lifetimes , 107 yr associated with a spreading wave of star formation which began some 3 × 108 yr ago. A population of high-mass X-ray binaries provides a simple model: donor stars of initial masses M2, 15 M, transfer mass on their thermal time-scales to black holes of masses M1, 10 M,. For alternative explanations of the Cartwheel ULX population in terms of intermediate-mass black holes (IMBHs) accreting from massive stars, the inferred production rate ,10,6 yr,1 implies at least 300 IMBHs, and more probably 3 × 104, within the star-forming ring. These estimates are increased by factors of ,,1 if the efficiency , with which IMBHs find companions of ,15 M, within 107 yr is <1. Current models of IMBH production would require a very large mass (,1010 M,) of stars to have formed new clusters. Further, the accretion efficiency must be low (, 6 × 10,3) for IMBH binaries, suggesting super-Eddington accretion, even though intermediate black hole masses are invoked with the purpose of avoiding it. These arguments suggest either that, to make a ULX, an IMBH must accrete from some as yet unknown non-stellar mass reservoir with very specific properties, or that most if not all ULXs in star-forming galaxies are high-mass X-ray binaries. [source] Levodopa in the treatment of Parkinson's disease: Current controversiesMOVEMENT DISORDERS, Issue 9 2004C. Warren Olanow Abstract Levodopa is the most effective symptomatic agent in the treatment of Parkinson's disease (PD) and the "gold standard" against which new agents must be compared. However, there remain two areas of controversy: (1) whether levodopa is toxic, and (2) whether levodopa directly causes motor complications. Levodopa is toxic to cultured dopamine neurons, and this may be a problem in PD where there is evidence of oxidative stress in the nigra. However, there is little firm evidence to suggest that levodopa is toxic in vivo or in PD. Clinical trials have not clarified this situation. Levodopa is also associated with motor complications. Increasing evidence suggests that they are related, at least in part, to the short half-life of the drug (and its potential to induce pulsatile stimulation of dopamine receptors) rather than to specific properties of the molecule. Treatment strategies that provide more continuous stimulation of dopamine receptors provide reduced motor complications in MPTP monkeys and PD patients. These studies raise the possibility that more continuous and physiological delivery of levodopa might reduce the risk of motor complications. Clinical trials to test this hypothesis are underway. We review current evidence relating to these areas of controversy. © 2004 Movement Disorder Society [source] Intraply and interply hybrid composites based on E-glass and poly(vinyl alcohol) woven fabrics: tensile and impact propertiesPOLYMER INTERNATIONAL, Issue 9 2004Prof Alessandro Pegoretti Abstract E-glass and poly(vinyl alcohol) (PVA) fibres were used to produce both homogeneous and hybrid composites with an orthophthalic unsatured polyester resin. Results are presented regarding the tensile and impact behaviour of both intraply and interply hybrid composites, with particular regard to the effects of the plies stacking sequence and the loading direction. With a proper choice of composition and stacking sequence, E-glass/PVA hybrid composites were proved to achieve a property profile superior to those of homogeneous E-glass laminates in terms of specific properties. In particular, hybridization with PVA fibres resulted in improving the specific impact energy of E-glass laminates. Resistance to impact crack propagation was higher for intraply with respect to interply hybrid composites, as evidenced by their ductility index values. Copyright © 2004 Society of Chemical Industry [source] G-protein-coupled receptor oligomers: two or more for what?THE JOURNAL OF PHYSIOLOGY, Issue 22 2009GABAB receptors, Lessons from mGlu G-protein-coupled receptors (GPCRs) are key players in the precise tuning of intercellullar communication. In the brain, both major neurotransmitters, glutamate and GABA, act on specific GPCRs [the metabotropic glutamate (mGlu) and GABAB receptors] to modulate synaptic transmission. These receptors are encoded by the largest gene family, and have been found to associate into both homo- and hetero-oligomers, which increases the complexity of this cell communication system. Here we show that dimerization is required for mGlu and GABAB receptors to function, since the activation process requires a relative movement between the subunits to occur. We will also show that, in contrast to the mGlu receptors, which form strict dimers, the GABAB receptors assemble into larger complexes, both in transfected cells and in the brain, resulting in a decreased G-protein coupling efficacy. We propose that GABAB receptor oligomerization offers a way to increase the possibility of modulating receptor signalling and activity, allowing the same receptor protein to have specific properties in neurons at different locations. [source] Flashbulb and factual memories: the case of Rabin's assassinationAPPLIED COGNITIVE PSYCHOLOGY, Issue 5 2003Israel Nachson Similarities and differences between factual memories (FTM) and flashbulb memories (FBM) of the assassination of Israel's Prime Minister, Itzhak Rabin, were explored. About two weeks after the assassination 61 Israeli students filled out a questionnaire which focused on the event and the circumstances in which they had first learned about it. About 11 months later they filled out again the same questionnaire, and self-assessed their emotional and cognitive reactions to the assassination, as well as specific properties of their memory; such as confidence in its accuracy, and the amounts of rehearsals and visual representations. Comparative analysis of the participants' responses on the two questionnaires uncovered decrements of about 25% in FTM accuracy, and about 36% in FBM consistency. Rehearsals and visual representations were more common in FTM than in FBM, but the levels of confidence in memory accuracy were similar for both. FTM which were presumably based on information provided by television broadcasts, appeared to have episodic properties. The data seem to support the hypothesis that FTM and FBM of traumatic public events are encoded together; perhaps by the same memory mechanism. Copyright © 2003 John Wiley & Sons, Ltd. [source] The emergence of interdisciplinary knowledge in problem-focused researchAREA, Issue 4 2009Anna Wesselink In this paper I explore the specific properties associated with the new knowledge produced by inter- or transdisciplinary research. Using my analysis of a land use planning study in the Meuse valley in The Netherlands, I argue that the process of knowledge integration requires the exercise of value judgement and that the outcomes are emergent. I also show that the selection of a boundary object as objective facilitates interdisciplinary research because it is shared amongst disciplines and because it necessitates judgement in its implementation. [source] Pannexins, distant relatives of the connexin family with specific cellular functions?BIOESSAYS, Issue 9 2009Catheleyne D'hondt Abstract Intercellular communication (IC) is mediated by gap junctions (GJs) and hemichannels, which consist of proteins. This has been particularly well documented for the connexin (Cx) family. Initially, Cxs were thought to be the only proteins capable of GJ formation in vertebrates. About 10 years ago, however, a new GJ-forming protein family related to invertebrate innexins (Inxs) was discovered in vertebrates, and named the pannexin (Panx) family. Panxs, which are structurally similar to Cxs, but evolutionarily distinct, have been shown to be co-expressed with Cxs in vertebrates. Both protein families show distinct properties and have their own particular function. Identification of the mechanisms that control Panx channel gating is a major challenge for future work. In this review, we focus on the specific properties and role of Panxs in normal and pathological conditions. [source] | ||||||||||||||||||||||||||||||||||||||||