Fearful facial expressions tend to be more salient than other expressions. This threat bias is to some extent driven by simple low-level image properties, rather than the high-level emotion ...interpretation of stimuli. It might be expected therefore that different expressions will, on average, have different physical contrasts. However, studies tend to normalise stimuli for RMS contrast, potentially removing a naturally-occurring difference in salience. We assessed whether images of faces differ in both physical and apparent contrast across expressions. We measured physical RMS contrast and the Fourier amplitude spectra of 5 emotional expressions prior to contrast normalisation. We also measured expression-related differences in perceived contrast. Fear expressions have a steeper Fourier amplitude slope compared to neutral and angry expressions, and consistently significantly lower contrast compared to other faces. This effect is more pronounced at higher spatial frequencies. With the exception of stimuli containing only low spatial frequencies, fear expressions appeared higher in contrast than a physically matched reference. These findings suggest that contrast normalisation artificially boosts the perceived salience of fear expressions; an effect that may account for perceptual biases observed for spatially filtered fear expressions.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
It has been argued that rapid visual processing for fearful face expressions is driven by the fact that effective contrast is higher in these faces compared to other expressions, when the contrast ...sensitivity function is taken into account. This proposal has been upheld by data from image analyses, but is yet to be tested at the behavioural level. The present study conducts a traditional contrast sensitivity task for face images of various facial expressions. Findings show that visual contrast thresholds do not differ for different facial expressions We re-conduct analysis of faces' effective contrast, using the procedure developed by Hedger, Adams and Garner, and show that higher effective contrast in fearful face expressions relies on face images first being normalised for RMS contrast. When not normalised for RMS contrast, effective contrast in fear expressions is no different, or sometimes even lower, compared to other expressions. However, the effect of facial expression on detection in a backward masking study did not depend on the type of contrast normalisation used. These findings are discussed in relation to the implications of contrast normalisation on the salience of face expressions in behavioural and neurophysiological experiments, and also the extent that natural physical differences between facial stimuli are masked during stimulus standardisation and normalisation.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Particle size does not affect the intrinsic activity of silica-supported nickel nanoparticles in dry reforming at 500°C. Display omitted
► Different silica supported nickel catalyst prepared with ...varying particle size (1.6–7.3nm). ► Neutral silica support favours a very high reduction degree (> 90%) at 500°C. ► Intrinsic Ni/SiO2 performances are independent of nickel particle size in dry reforming at 773K. ► The H2/CO ratio is controlled by the thermodynamic of the fast reverse water gas shift reaction.
The influence of nickel particle size in the range of 1.6–7.3nm on catalyst performance in low temperature CO2 reforming of methane reaction has been investigated using well-defined catalysts based on a neutral silica support. XAS and XPS studies indicated a reduction degree greater than 90%. The intrinsic Ni/SiO2 performances were found to be independent of nickel particle size in dry reforming at 773K using a CH4/CO2 ratio of 1.3 at 1atm, both at an early stage and in steady state conditions. The H2/CO ratio was also found to be structure in sensitive but is controlled by thermodynamics through the faster reverse water gas shift reaction.
Inelastic neutron scattering (INS) is employed to examine the evolution of a promoter-free iron-based Fischer–Tropsch synthesis catalyst (∼10 g catalyst charge) that is exposed to ambient pressure CO ...hydrogenation at 623 K for up to 10 days time-on-stream (T-o-S). The longer reaction time is selected to better understand how the formation of a previously described hydrocarbonaceous overlayer corresponds to the catalyst conditioning process. Although the onset of pseudo steady-state reactor performance is observed at approximately 9 h T-o-S, INS establishes that the intensity of the C–H stretching mode of the sp3-hybridized component of the hydrocarbonaceous overlayer saturates at about 24 h T-o-S, while the corresponding intensity of the C–H stretching mode of the sp2-hybridized component requires 100–200 h T-o-S to achieve saturation. This novel series of measurements reveal different aspects of the complex catalyst evolutionary process to be indirectly connected with catalytic turnover.
The importance of amorphous calcium carbonate (ACC) as a precursor phase in the biomineralization of marine calcifiers is increasingly being reported, particularly as the presence of ACC has been ...observed or inferred in several major groups. Here, we investigate the structure of ACC and the conditions required for its precipitation from seawater-based solutions, with an emphasis on the coinfluence of the carbonate system (pH, dissolved inorganic carbon (DIC) concentration), seawater Mg/Ca ratio, and presence of amino acids. We find that Mg2+ and the presence of aspartic acid, glutamic acid, and glycine strongly inhibit ACC precipitation. Moreover, we were unable to precipitate ACC from seawater with a carbonate chemistry within the range of that thought to characterize the calcification site of certain marine calcifiers (i.e., DIC < 6 mM, pH < 9.3), although substantial modification of the seawater Mg/Ca ratio (Mg/Casw) allowed precipitation at a reduced DIC with the implication that this could be an important component of utilizing an ACC pathway. In addition, the degree to which Mg/Casw and the presence of amino acids influences the structure of ACC and the necessary seawater CO3 2– for precipitation is strongly pH dependent. At lower, more biologically relevant pH than that typical of much inorganic work, decreasing Mg/Casw can result in greater long-range order and less water of crystallization but facilitates precipitation at a considerably lower CO3 2– than at higher pH.
Glycosylceramides in mammalian species are thought to be present in the form of β-anomers. This conclusion was reinforced by the identification of only one glucosylceramide and one galactosylceramide ...synthase, both β-transferases, in mammalian genomes. Thus, the possibility that small amounts of α-anomers could be produced by an alternative enzymatic pathway, by an unfaithful enzyme, or spontaneously in unusual cellular compartments has not been examined in detail. We approached the question by taking advantage of the exquisite specificity of T and B lymphocytes and combined it with the specificity of catabolic enzymes of the sphingolipid pathway. Here, we demonstrate that mammalian immune cells produce constitutively very small quantities of α-glycosylceramides, which are the major endogenous ligands of natural killer T cells. Catabolic enzymes of the ceramide and glycolipid pathway tightly control the amount of these α-glycosylceramides. The exploitation of this pathway to manipulate the immune response will create new therapeutic opportunities.
•α-linked monoglycosylceramides are endogenous ligands of NKT cells•Mammalian cells can produce small amounts of α-linked monoglycosylceramides•Catabolic enzymes control the amount of α-galactosylceramides in cells•Synthetic β-glycosylceramides are often contaminated with α-anomers
The α-anomeric form of lipids is a potent trigger of NKT cell activation but is not thought to be synthesized by mammalian cells. Teyton and colleagues show that mammalian cells can produce small amounts of α-linked monoglycosylceramides.
The present study explores the threat bias for fearful facial expressions using saccadic latency, with a particular focus on the role of low-level facial information, including spatial frequency and ...contrast. In a simple localisation task, participants were presented with spatially-filtered versions of neutral, fearful, angry and happy faces. Together, our findings show that saccadic responses are not biased toward fearful expressions compared to neutral, angry or happy counterparts, regardless of their spatial frequency content. Saccadic response times are, however, significantly influenced by the spatial frequency and contrast of facial stimuli. We discuss the implications of these findings for the threat bias literature, and the extent to which image processing can be expected to influence behavioural responses to socially-relevant facial stimuli.
Perceptual biases for fearful facial expressions are observed across many studies. According to the low-level, visual-based account of these biases, fear expressions are advantaged in some way due to ...their image properties, such as low spatial frequency content. However, there is a degree of empirical disagreement regarding the range of spatial frequency information responsible for perceptual biases. Breaking continuous flash suppression (b. CFS) has explored these effects, showing similar biases for detecting fearful facial expressions. Recent findings from a b. CFS study highlight the role of high, rather than low spatial frequency content in determining faces' visibility. The present study contributes to ongoing discussions regarding the efficacy of b. CFS, and shows that the visibility of facial expressions vary according to how they are normalised for physical contrast and spatially filtered. Findings show that physical contrast normalisation facilitates fear's detectability under b. CFS more than when normalised for apparent contrast, and that this effect is most pronounced when faces are high frequency filtered. Moreover, normalising faces' perceived contrast does not guarantee equality between expressions' visibility under b. CFS. Findings have important implications for the use of contrast normalisation, particularly regarding the extent to which contrast normalisation facilitates fear bias effects.
The challenges associated with synthesizing porous materials mean that new classes of zeolites (zeotypes)-such as aluminosilicate zeolites and zeolite analogues-together with new methods of preparing ...known zeotypes, continue to be of great importance. Normally these materials are prepared hydrothermally with water as the solvent in a sealed autoclave under autogenous pressure. The reaction mixture usually includes an organic template or 'structure-directing agent' that guides the synthesis pathway towards particular structures. Here we report the preparation of aluminophosphate zeolite analogues by using ionic liquids and eutectic mixtures. An imidazolium-based ionic liquid acts as both solvent and template, leading to four zeotype frameworks under different experimental conditions. The structural characteristics of the materials can be traced back to the solvent chemistry used. Because of the vanishingly low vapour pressure of ionic liquids, synthesis takes place at ambient pressure, eliminating safety concerns associated with high hydrothermal pressures. The ionic liquid can also be recycled for further use. A choline chloride/urea eutectic mixture is also used in the preparation of a new zeotype framework.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A series of tert-butyl-substituted pincer ligands based on 1,3-diaminobenzene and 3-aminophenol scaffolds, tBu4PXCYP (1e, X = Y = NH; 1f, X = NH; Y = O) and the corresponding iridium hydridochloro ...complexes (tBu4PXCYP)IrHCl (2e, X = Y = NH; 2f, X = NH; Y = O) were prepared with moderate yields and high purity and were fully characterized by 1H and 31P NMR spectroscopy. Unsymmetrical hybrid pincer ligands R2PNCOPtBu2 (1g, R = isopropyl; 1h, R = cyclohexyl) were prepared conveniently in high yield via a one-pot procedure by judiciously choosing reaction conditions and base; the corresponding iridium hydrido chloro complexes iPr2PNCOPtBu2IrHCl (2g) and Cy2PNCOPtBu2IrHCl (2h) were synthesized by the reaction of IrCl(COE)22 with ligands. X-ray crystallography reveals that these iridium pincer complexes adopt similar square-pyramidal geometries and exhibit strong intermolecular hydrogen bonding between the NH linker and chloride ions of the adjacent iridium complex in the solid state. 1H NMR chemical shifts of tert-butyl based pincer ligated iridium hydrides move downfield when the electronegativity of the linker between the benzene backbone and phosphine moiety increases for 2a, 2e, 2f, and 2b. Accordingly the corresponding iridium pincer carbonyl complexes (tBu4PXCYP)Ir(CO), 3a, 3e, 3f, and 3b show a blue shift in the CO stretching frequency. The activities of iridium complexes containing NH linkers were briefly examined for transfer dehydrogenation from cyclooctane to tert-butylethylene; (iPr2PNCOPtBu2)IrHCl (2g) exhibits the highest activity among all tested iridium pincer complexes, including the most studied (tBu4PCP)IrHCl (2a) and (tBu4POCOP)IrHCl (2b). The enhanced catalytic activity could be related to combined electronic and steric effects of the NH/O hybrid linker and different alkyl groups at phosphorus. This new class of iridium pincer complexes could have great implications in catalytic transformation of polar compounds due to the strong hydrogen-bond-donating ability of the NH linker.
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