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Profound Insights (profound + insight)
Selected AbstractsBrittle,ductile transition in the PETG/PC blends by adding PTW elastomerPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2010Xinlan Zhang Abstract In this paper, an elastomer containing epoxy groups, ethylene-butylacrylate-glycidylmethacrylate (PTW), was used as toughening modifier for the poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG)/polycarbonate (PC) blends. A remarkable improvement of toughness was achieved by addition of only 5,wt% PTW. In particular, an obvious brittle,ductile (B,D) transition in impact toughness was found when the PTW content increased from 3 to 5,wt%. The toughening mechanism and observed B,D transition have been explored in detail, combining with electronic microscopy observation, melt rheological investigation and dynamic mechanical analysis (DMA). It is suggested that the B,D transition can be attributed to a better interfacial adhesion between different phases, and importantly, to a continuum percolation dispersed-phases network formed at appropriate PTW content, in which PC particles are connected with each other by PTW phase. Our present study offers new, profound insight on the toughening mechanism for the elastomer modified amorphous/amorphous plastic blends. Copyright © 2009 John Wiley & Sons, Ltd. [source] Compounds with a `stuffed' anti-bixbyite-type structure, analysed in terms of the Zintl,Klemm and coordination-defect conceptsACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2009Angel Vegas The bixbyite structure (Mn2O3) () is often described as a distorted face-centered cubic (f.c.c.) array of Mn atoms, with O atoms occupying 3/4 of the tetrahedral holes. The empty M4 tetrahedra are centred at 16c. In anti-bixbyite structures (Mg3N2), cation vacancies are centred in empty N4 tetrahedra. If 16 hypothetical atoms were located at this site they would form the structure of ,-Si. This means that anti-bixbyite structures are ideally prepared to accommodate Si(Ge) atoms at these holes. Several compounds (Li3AlN2 and Li3ScN2) fully satisfy this expectation. They are really anti-bixbyites `stuffed' with Al(Sc). The presence of these atoms in 16c is illuminated in the light of the extended Zintl,Klemm concept (EZKC) [Vegas & García-Baonza (2007). Acta Cryst. B63, 339,345], from which a compound would be the result of `multiple resonance' pseudo-structures, emerging from electron transfers between any species pair (like or unlike atoms, cations or anions). The coordination-defect (CD) concept [Bevan & Martin (2008). J. Solid State Chem.181, 2250,2259] is also consistent with the EZKC description of the pseudo-structures. A more profound insight into crystal structures is gained if one is not restricted to the contemplation of classical anions and cations in their conventional oxidation states. [source] Toward a New Sexual Selection Paradigm: Polyandry, Conflict and Incompatibility (Invited Article)ETHOLOGY, Issue 12 2003Jeanne A. Zeh Darwin's recognition that male,male competition and female choice could favor the evolution of exaggerated male traits detrimental to survival set the stage for more than a century of theoretical and empirical work on sexual selection. While this Darwinian paradigm represents one of the most profound insights in biology, its preoccupation with sexual selection as a directional evolutionary force acting on males has diverted attention away from the selective processes acting on females. Our understanding of female reproduction has been further confounded by discreet female mating tactics that have perpetuated the illusion of the monogamous female and masked the potential for conflict between the sexes. With advances in molecular techniques leading to the discovery that polyandry is a pervasive mating strategy, recognition of these shortcomings has brought the study of sexual selection to its current state of flux. In this paper, we suggest that progress in two key areas is critical to formulation of a more inclusive, sexual selection paradigm that adequately incorporates selection from the female perspective. First, we need to develop a better understanding of male × female and maternal × paternal genome interactions and the role that polyandry plays in providing females with non-additive genetic benefits such as incompatibility avoidance. Consideration of these interaction effects influencing natural selection on females is important because they can complicate and even undermine directional sexual selection on males. Secondly, because antagonistic coevolution maintains a balance between opposing sides that obscures the conflict itself, many more experimental evolution studies and interventionist investigations (e.g. gene knockouts) are needed to tease apart male manipulative adaptations and female counter-adaptations. It seems evident that the divisiveness and controversy that has plagued sexual selection theory since Darwin first proposed the idea has often stalled progress in this important field of evolutionary biology. What is now needed is a more pluralistic and integrative approach that considers natural as well as sexual selection acting on females, incorporates multiple sexual selection mechanisms, and exploits advances in physiology and molecular biology to understand the mechanisms through which males and females achieve reproductive success. [source] Modulation of spinal inhibitory reflex responses to cutaneous nociceptive stimuli during upper limb movementEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2008Romildo Don Abstract In the present study we investigated the probability, latency and duration of the inhibitory component of the withdrawal reflex elicited by painful electrical stimulation of the index finger in humans. The stimulus consisted of a train of high-intensity pulses. The investigation was carried out in several upper limb muscles during isometric contractions of different strengths and during a motor sequence consisting of reaching, picking up and transporting an object. We used a new algorithm to detect and characterize the inhibitory reflex. The reflex was found in all muscles except the brachioradialis at all the isometric contraction strengths, and showed a distal-to-proximal gradient of latency and duration. Conversely, during movement the reflex probability was high (> 80%) in the anterior deltoid and triceps muscles during reaching, in the extensor carpi radialis muscle during transporting of the object, and in the first interosseous muscle during both picking up and transporting of the object. This modulation of inhibitory reflex transmission in the upper limb muscles suggests that the motor response is organized in such a way as to inhibit the overall ongoing motor task by interrupting motion during reaching and by releasing the object during transporting. This pattern of modulation appears to differ markedly from that previously reported for the excitatory component of the withdrawal reflex. Study of the nociceptive inhibitory reflexes during movement offers new and more profound insights into the functional anatomical organization of the spinal interneuronal network mediating sensory,motor integration. [source] IL-5-induced airway eosinophilia , the key to asthma?IMMUNOLOGICAL REVIEWS, Issue 1 2001Eckard Hamelmann Summary: Bronchial asthma is a chronic inflammatory airway disease defined by reversible airway obstruction and non-specific airway hyper-responsiveness (AHR). Although profound insights have been made into the pathophysiology of asthma, the exact mechanisms inducing and regulating the disease are still not fully understood. Yet, it is generally accepted that the pathological changes in asthma are induced by a chronic inflammatory process which is characterized by infiltration of the bronchial mucosa with lymphocytes and eosinophils, increased mucus production and submucosal edema. There is increasing evidence that an imbalance in the T-helper (Th) cell response of genetically predisposed individuals to common environmental antigens plays a pivotal role in the pathogenesis of allergic bronchial asthma and other atopic disorders. Following allergic sensitization, T cells from atopic patients tend to produce elevated levels of Th2-type cytokines, especially interleukin (IL)-4, IL-13, IL-5 and IL-6, which induce and regulate IgE production and eosinophil airway infiltration. In this review, the role of Th2-type cytokines, IgE and airway eosinophils in the induction of airway inflammation and AHR is discussed, and animal studies of asthma and AHR, mainly in rodents will be considered. A better understanding of the underlying mechanisms leading to asthma pathology may yield more specific immunological strategies for the treatment of this disease which is increasing worldwide. I thank the many colleagues in the laboratory of Dr. E. W. Gelfand, National Jewish Research Center, Denver CO, USA, for continuous support and encouragement. E.H. is a fellow of the Deutsche Forschungsgemeinschaft (DFG Ha 2162/1-1 and 2-1). [source] ACKNOWLEDGING A HIDDEN GOD: A THEOLOGICAL CRITIQUE OF STANLEY CAVELL ON SCEPTICISMTHE HEYTHROP JOURNAL, Issue 3 2007JUDITH E. TONNING In his early work, the philosopher Stanley Cavell offers a sustained engagement with the threat of epistemological scepticism, shaped by the intuition that although (as the late Wittgenstein shows) ordinary language use is the practice within which alone meaning is possible (and which can thus not be further analysed or rationalised), it is also a basic human inclination to wish to escape the limitations of the ,ordinary'. This, for Cavell, is the root of scepticism. Scepticism, on this view, thus appears not primarily as an epistemological but as an (injurious) moral stance, which cannot be refuted but must be continually confronted and overcome. Vis-à-vis scepticism, ,acknowledgement' is the practice-based recognition of the world and other people in their continuing elusiveness, which ineluctably involves risk, but just so is the only way of knowing that is appropriate to and honours the (finite) human condition. One problematic aspect of this (very fertile) approach is that Cavell's secular viewpoint makes it difficult for him to say both why the desire for a ,beyond' arises in the first place, and why its expression as denial is morally wrong (rather than merely misguided). His approach thus invites a theological ,supplementation' which grounds the human condition in an original and real relation to God that is meant to draw the believer, through Christ, into the divine life itself. Such a reinterpretation both elucidates the concepts of scepticism and acknowledgement, and makes these concepts available for a theological outlook that is able to accommodate Cavell's profound insights into ,the human'. [source] | ||||||||||