Home About us Contact
|
Home About us Contact | ||
|
|
||
Satisfactory Explanation (satisfactory + explanation)
Selected AbstractsRapid crystal growth without inherent supersaturation induced by nanoscale fluid flows?CRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2006M. J. Jones Abstract Crystal growth is a process that only takes place under non-equilibrium conditions and a necessary prerequisite is that the crystal is exposed to a phase that is supersaturated in the material the crystal is composed of, be it a solution, a vapour or a supercooled melt. In industrial mass crystallization the growth rate for a population of crystals (in suspension growth processes [1]) rarely exceeds mean linear velocities of 10 -7 ms -1. Here we present a mass crystallization process which is accompanied by rapid crystal growth several orders of magnitude faster and into a region of solution that is without inherent supersaturation. The material investigated is a solid hydrate that exhibits a solution mediated phase transition to its anhydrous form in the presence of methanol [2]. The phase transition is initiated simply by placing an amount of hydrate crystals into the solvent and is characterized by the rapid emergence of needle-shaped crystals. The needles emanate from the crystal faces of the hydrate crystals and grow into the solution, which is nominally free of the substance to be crystallized. The high growth rate of the crystals, which of the order of up to 10 -4 ms -1 is surprising. Although rapid needle growth has been observed before [3-9], to date a satisfactory explanation for needles growing under the abovementioned conditions is still outstanding. Based upon the topology of the crystals we propose a tentative mechanism for this phenomenon capable of explaining the unusually rapid growth and highlight those questions that need addressing in order to verify this mechanism. X-ray powder diffraction is used to characterize the crystal phase of the needles; confocal fluorescence microscopy reveals that the needles are hollow. The width of these needles is between 0.5 and 5 ,m, their length appears to be limited only by the amount of hydrate available for their formation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Differential growth and multicellular villi direct proepicardial translocation to the developing mouse heartDEVELOPMENTAL DYNAMICS, Issue 1 2008Laurel S. Rodgers Abstract In the mammalian system the proepicardium (PE) arises from mesothelium of the septum transversum before translocation to the heart where it forms the epicardium and progenitor cells of the coronary vessels. Despite its importance, the process in which PE cells translocate to the myocardium in mammals is not well defined. The current paradigm states that cellular cysts of PE float across the pericardial space and contact the outer surface of the myocardium. This mechanism does not provide a satisfactory explanation for the directionality or localization of PE migration. To better define PE migration, we performed a detailed study of mouse PE development. We provide thorough documentation that redefines the size of the PE migratory field and the mechanism of migration. Our new model incorporates differential growth and direct contact between multicellular PE villi and the myocardium as mechanisms in formation of the epicardium. Developmental Dynamics 237:145,152, 2008. © 2007 Wiley-Liss, Inc. [source] Concentration dependency of biota-sediment accumulation factors for chlorinated dibenzo- p -dioxins and dibenzofurans in dungeness crab (Cancer magister) at marine pulp mill sites in British Columbia, CanadaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2000Walter J. Cretney Abstract Biota-sediment accumulation factors (BSAFs) for some chlorinated dibenzo- p -dioxin and dibenzofuran congeners (PCDD/Fs) in Dungeness crab (Cancer magister) hepatopancreas and associated sediments are concentration independent as required by equilibrium partition models. In particular 2, 3, 7, 8-tetrachlorodibenzo- p -dioxin (2, 3, 7, 8-TCDD), 2, 3, 7, 8-tetrachlorodibenzofuran, the 2, 3, 7, 8-substituted pentachlorodibenzofurans, and the non-2, 3, 7, 8-hexachlorodibenzofurans (HxCDFs) seem to fall into this group. The BSAFs for other isomers exhibit significant, nonlinear variations with sediment or crab PCDD/F concentrations. For some of these other isomers (e.g., the non-2, 3, 7, 8 TCDDs and possibility the 2, 3, 7, 8-substituted HxCDFs), association of a variable fraction of the total present with soot carbon may provide a satisfactory explanation for the concentration behavior. For the HxCDDs we propose that the nonlinear concentration behavior may arise from the thermodynamic properties of fluids confined in hydrophobic voids within particulate and colloidal material produced by the pulp mills. The nonlinear relationship between BSAFs and PCDD/F concentrations greatly complicates prediction of the potential for dioxin and furan bioaccumulation in crabs and the formulation of sediment quality criteria. We provide a nonlinear equation relating toxic equivalency and sediment concentrations. [source] Spinoza on the Problem of AkrasiaEUROPEAN JOURNAL OF PHILOSOPHY, Issue 1 2010Eugene Marshall Though each is intuitive in a certain way, they both fail as explanations of the most interesting cases of akrasia. Spinoza's own thoughts on bondage and the affects follow, from which a Spinozist explanation of akrasia is constructed. This account is based in Spinoza's mechanistic psychology of cognitive affects. Because Spinoza's account explains action asissuing from modes of mind that are both cognitive and affective, it captures the intuitions that motivate the two traditional views while avoiding the pitfalls that result from their one-sided approaches. This project will allow us a fuller understanding of Spinozist moral psychology. In addition to this historical value, the Spinozist theory may offer a satisfactory explanation of certain hard cases of akrasia while avoiding the problems be set by other theories. For this reason, the Spinozist account could also be seen as a useful contribution to our philosophical understanding of the phenomenon of akrasia. [source] The non-Gaussian nature of bibliometric and scientometric distributions: A new approach to interpretationJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 13 2001Ludmila E. Ivancheva An attempt has been made to give an answer to the question: Why do most bibliometric and scientometric laws reveal characters of Non-Gaussian distributions, i.e., have unduly long "tails"? We tried to apply the approach of the so-called "Universal Law," discovered by G. Stankov (1997, 1998). The basic principle we have used here is that of the reciprocity of energy and space. A new "wave concept" of scientific information has been propounded, in which terms the well-known bibliometric and scientometric distributions find a rather satisfactory explanation. One of the made corollaries is that , = 1 is the most reasonable value for the family of Zipf laws, applied to information or social phenomena. [source] Deep spectroscopy of the FUV,optical emission lines from a sample of radio galaxies at z, 2.5: metallicity and ionization,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008A. Humphrey ABSTRACT We present long-slit near-infrared (NIR) spectra, obtained using the Infrared Spectrometer And Array Camera (ISAAC) instrument at the Very Large Telescope, which sample the rest-frame optical emission lines from nine radio galaxies at z, 2.5. One-dimensional spectra have been extracted and, using broad-band photometry, have been cross-calibrated with spectra from the literature to produce line spectra spanning a rest wavelength of ,1200,7000 Ĺ. The resulting line spectra have a spectral coverage that is unprecedented for radio galaxies at any redshift. We have also produced a composite of the rest-frame ultraviolet (UV),optical line fluxes of powerful, z, 2.5 radio galaxies. We have investigated the relative strengths of Ly,, H,, H,, He ii,1640 and He ii,4687, and we find that Av can vary significantly from object to object. In addition, we have identified new line ratios to calculate electron temperature: [Ne v],1575/[Ne v],3426, [Ne iv],1602/[Ne iv],2423, O iii],1663/[O iii],5008 and [O ii],2471/[O ii],3728. We calculate an average O iii temperature of 14100+1000,600 K. We have modelled the rich emission line spectra, and we conclude that they are best explained by active galactic nucleus (AGN) photoionization with the ionization parameter U varying between objects. For shock models (with or without the precursor) to provide a satisfactory explanation for the data, an additional source of ionizing photons is required , presumably the ionizing radiation field of the AGN. Single slab photoionization models are unable to reproduce the high- and the low-ionization lines simultaneously: the higher ionization lines imply higher U than do the lower ionization lines. This problem may be alleviated either by combining two or more single slab photoionization models with different U, or by using mixed-medium models such as those of Binette, Wilson & Storchi-Bergmann. In either case, U must vary from object to object. On the basis of N v/N iv] and N iv]/C iv we argue that, while photoionization is the dominant ionization mechanism in the extended emission line regions (EELR), shocks make a fractional contribution (,10 per cent) to its ionization. The N v/N iv] and N iv]/C iv ratios in the broad-line region (BLR) of some quasars suggest that shock ionization may be important in the BLR also. We find that in the EELR of z, 2 radio galaxies the N/H abundance ratio is close to its solar value. We conclude that N/H and metallicity do not vary by more than a factor of 2 in our sample. These results are consistent with the idea that the massive ellipticals which become the hosts to powerful AGN are assembled very early in the history of the universe, and then evolve relatively passively up to the present day. [source] Sex ratio and associated risk factors for 50 congenital anomaly types: Clues for causal heterogeneityBIRTH DEFECTS RESEARCH, Issue 1 2004Monica Rittler Abstract BACKGROUND Sex ratio (SR) deviations have been reported for many congenital anomalies, but so far no satisfactory explanation for these deviations has been found. The aim of this study was to detect sex-related differences in the association between risk factors and congenital anomalies, and to relate these differences with possibly underlying causes of birth defects. METHODS Between 1982 and 1999, 1,444,646 newborn infants were examined by the Estudio Colaborativo Latino Americano de Malformaciones Congénitas (ECLAMC) network of South American maternity hospitals. Male relative risks were established for 39,425 infants with 50 selected single anomalies. Associations between male sex and risk factors were identified in nonmalformed infants. In malformed infants, sex-related risk differences were established, and the SR of these infants, with and without associated risk factors, were compared. RESULTS Infants with neural tube defects (NTDs) and intrauterine growth restriction had a lower SR than those with normal growth, while spina bifida without hydrocephaly (SB[sHy]) was the only NTD subtype without a significant female predominance. Multigravidity lowered the SR of SB(sHy) and HPP (HPP) cases. Increased paternal age inverted the SR of cleft lip (CL) with or without cleft palate (CL[P]) cases from male to female. CONCLUSIONS The results indicate etiological differences between high and low SB, a stronger relationship between multigravidity and female sex of the offspring than between multigravidity and a specific congenital anomaly, and a possible involvement of dominant mutations for CL(P), as suggested by the association with increased paternal age. Birth Defects Research (Part A) 67:000,000, 2003. © 2003 Wiley-Liss, Inc. [source] Photophysical Properties of Heteroleptic Iridium Complexes Containing Carbazole-Functionalized ,-DiketonatesCHEMPHYSCHEM, Issue 4 2008Zhiwei Liu Abstract Twelve iridium complexes with general formula of Ir(C^N)2(LX) [C^N represents the cyclometalated ligand, i.e. 2-(2,4-difluorophenyl) pyridine (dfppy), 2-phenylpyridine (ppy), dibenzo{f, h}quinoxaline (DBQ); LX stands for ,-diketonate, i.e. acetyl acetonate (acac), 1-(carbazol-9-yl)-5,5-dimethylhexane-2,4-diketonate (CBDK), 1-(carbazol-9-yl)-5,5,6,6,7,7,7-heptafluoroheptane-2,4-diketonate (CHFDK), 1-(N-ethyl-carbazol-3-yl)-4,4,5,5,6,6,6-heptafluorohexane-1,3-diketonate (ECHFDK)] are synthesized, characterized and their photophysical properties are systemically studied. In addition, crystals of Ir(DBQ)2(CHFDK) and Ir(DBQ)2(acac) are obtained and characterized by single crystal X-ray diffraction. The choice of these iridium complexes provides an opportunity for tracing the effect of the triplet energy level of ancillary ligands on the photophysical and electrochemical behaviors. Data show that if the triplet energy level of the ,-diketonate is higher than that of the Ir(C^N)2 fragment and there is no superposition on the state density map, strong 3LC or 3MLCT-based phosphorescence can be obtained. Alternatively, if the state density map of the two parts are in superposition, the 3LC or 3MLCT-based transition will be quenched at room temperature. Density functional theory calculations show that these complexes can be divided into two categories. The lowest excited state is mainly determined by C^N but not ,-diketonate when the difference between the triplet energy levels of the two parts is large. However, when this difference is very small, the lowest excited state will be determined by both sides. This provides a satisfactory explanation for the experimental observations. [source] Parents' use and views of the national standard Personal Child Health Record: a survey in two primary care trustsCHILD: CARE, HEALTH AND DEVELOPMENT, Issue 6 2007S. Walton Abstract Background The Personal Child Health Record (PCHR) is a booklet given to parents in the UK, following the birth of a child, to be used as the main record of their growth, development and uptake of preventative health services. The national standard PCHR has been available since April 2004. The aim of this survey was to explore parental views of the ,new' PCHR, their experiences in receiving it, and its subsequent use, focusing on specific issues of current debate among health professionals. Methods A parental questionnaire (n = 89) was administered in July 2004, in 10 child health clinics located in two primary care trusts; one in central London and the other in Buckinghamshire. Results Nearly all parents (98%) reported that they used the PCHR as a record of their child's health and development and 92% reported that they ,always' took it with them when seeing healthcare staff about their child. Some parents (22%) indicated that they had not been given a satisfactory explanation as to how to use the PCHR, at the time it was issued to them. Parents reported that health visitors were more likely than other health professionals to use the PCHR both to obtain information about their child and to record information. The majority of respondents (78%) were happy for the level of maternal education to be documented in their child's PCHR. Conclusions Parents used, appreciated and liked the design of the national standard PCHR. Health visitors and primary care staff used the PCHR more than secondary care staff. The potential benefits of the PCHR will only be maximized if other healthcare professionals respond by using it. [source] Critical periods in the life cycle and the effects of a severe spate vary markedly between four species of elmid beetles in a small streamFRESHWATER BIOLOGY, Issue 8 2006J. M. ELLIOTT Summary 1. The chief objectives were: (i) to describe quantitatively the life cycles of four species of Elmidae, Elmis aenea, Esolus parallelepipedus, Oulimnius tuberculatus and Limnius volkmari; (ii) to use life tables to identify critical periods for survival in the life cycle of each species; (iii) to evaluate the immediate and longer-term effects of a severe spate on densities of the four species. Monthly samples were taken over 63 months at two contrasting sites in a small stream: one in a deep section with macrophytes abundant, and the other in a shallow stony section. 2. There were five larval instars for O. tuberculatus, seven for L. volkmari and six for the other two species. The life cycle of each species took 1 year from egg hatching (chiefly in June for E. aenea and O. tuberculatus, and July for the other species) to pupation in the stream bank and a further year before the adults in the stream matured and laid their eggs. Mature adults were present in most months, but were rare or absent in January and February and attained maximum densities in April for O. tuberculatus and May for the other species. 3. Laboratory experiments provided data on egg hatching and pupation periods and the number of eggs laid per female. Life tables compared maximum numbers per square metre for key life-stages. Within each species, mortality rates between adjacent life-stages were fairly constant among six cohorts and between sites, in spite of large differences in numbers. The only exception for all species was the high adult, but not larval, mortality during a severe spate. 4. Standardised life tables, starting with 1000 eggs, identified key life-stages with the highest mortality, namely the early life-stages for E. aenea (36% mortality), start of the overwintering period to pupation for O. tuberculatus (41%) and L. volkmari (51%), start of pupation to the maximum number of immature adults for E. parallelepipedus (41%) and between the maximum numbers of immature and mature adults for O. tuberculatus (41%). Therefore, critical periods for survival in the life cycle differed between species, presumably because of their different ecological requirements. Similarly, the effects of the spate on adult mortality, and hence egg production, varied between species, being most severe and long-term for E. aenea and O. tuberculatus, less severe for E. parallelepipedus and least severe with a rapid recovery for L. volkmari. Possible reasons for these discrepancies are discussed, but more data are required on the food and microhabitat requirements of the elmids before satisfactory explanations can be found. [source] Inequality and Theorizing in International Relations: The Case for Subaltern RealismINTERNATIONAL STUDIES REVIEW, Issue 3 2002Mohammed Ayoob I argue that the dominant paradigms in IR fail to explain adequately two of the central issues in the international system: the origins of the majority of conflicts and the behavior of the majority of states. These paradigms fail because they formulate generalizations from data drawn from a restricted universe and because they lack historical depth. Both these flaws are related to inequality in the arena of the production of knowledge in IR, which in turn is a function of the inequality in material capabilities in the international system. A supplementary, if not alternative, perspective is needed to correct this situation and fill this gap. We can fashion such a perspective by drawing upon classical realist thought, the historical sociology of state formation, and the normative perspicacity of the English School. Combining their insights and applying them to the analysis of Third World conflict patterns and the external and domestic behavior of Third World states is likely to provide more satisfactory explanations for the origins of the majority of contemporary conflicts. Such an exercise will also shed light on the crucial variables that determine the behavior of the majority of states in the Third World. Moving postcolonial states into the mainstream of theorizing in IR will also help reduce the impact of inequality on the field and open new vistas for theoretically informed scholarly research. I also call for pluralism in international relations theorizing rather than a search for universally applicable law,like generalizations divorced from historical and social contexts. [source] | ||||||||||||||||