Grain alignment theory has reached the stage where quantitative predictions of the degree of alignment and its variations with optical depth are possible. With the goal of studying the effect of ...clumpiness on submillimeter and far-infrared polarization, we have computed the polarization due to alignment via radiative torques within clumpy models of cores and molecular clouds. Our models were based on a highly inhomogeneous simulation of compressible MHD turbulence. A reverse Monte Carlo radiative transfer method was used to calculate the intensity and anisotropy of the internal radiation field, and the subsequent grain alignment was computed for a power-law size distribution of grains using the DDSCAT package for radiative torques. The intensity and anisotropy of the intracloud radiation field show large variations throughout the models but are generally sufficient to drive widespread grain alignment. The P-I relations for our models reproduce those seen in observations. We show that the degree of polarization observed is extremely sensitive to the upper grain size cutoff and is less sensitive to changes in the radiative anisotropy. Furthermore, despite a variety of dust temperatures along a single line of sight through our models and among dust grains of different sizes, the assumption of isothermality among the aligned grains does not introduce a significant error. Our calculations indicate that submillimeter polarization vectors can be reasonably good tracers for the underlying magnetic field structure, even for relatively dense clouds (Av similar to 10 to the cloud center). The current predictive power of the grain alignment theory should motivate future polarization observations using the next generation of multiwavelength submillimeter polarimeters such as those proposed for SOFIA.
We provide simple polynomial fits to the X-ray photoelectric cross-sections (0.03 keV < E < 10 keV) for mixtures of gas and dust found in protoplanetary disks. Using the solar elemental abundances of ...Asplund et al., we treat the gas and dust components separately, facilitating the further exploration of evolutionary processes such as grain settling and gain growth. We find that blanketing due to advanced grain growth (a max > 1 Delta *mm) can reduce the X-ray opacity of dust appreciably at EX ~ 1 keV, coincident with the peak of typical T Tauri X-ray spectra. However, the reduction of dust opacity by dust settling, which is known to occur in protoplanetary disks, is probably a more significant effect. The absorption of 1-10 keV X-rays is dominated by gas opacity once the dust abundance has been reduced to about 1% of its diffuse interstellar value. The gas disk establishes a floor to the opacity at which point X-ray transport becomes insensitive to further dust evolution. Our choice of fitting function follows that of Morrison & McCammon, providing a degree of backward compatibility.
We present calculations of the continuum ultraviolet radiation field (91.2 mn < lambda < 550 mn) penetrating both uniform and clumpy (3D turbulent supersonic magnetohydrodynamic) starless molecular ...gas layers. We find that despite the self-shielding of clumps, pristine (i.e., unreddened) radiation penetrates deeply both the cloud's volume and its mass, resulting in a brighter and bluer intracloud radiation field compared to that in an equivalent uniform cloud. Motivated by these results, we construct and test a toy model ray-tracing scheme for the radiative transfer that fits the UV-visible spectral range with a three-parameter function. We calculate the photoionization rates, Gamma , of the elements C, Na, Mg, Si, S, and Fe as functions of the visual extinction A sub(V) along lines of sight. Typically, the difference in Gamma (A sub(V)) between the clumpy and uniform clouds increases to orders of magnitude at even modest extinctions (A sub(V) similar to 2). Photoionization in the clumpy model extends 2-3 times deeper than in the uniform case, and it dominates cosmic-ray ionization throughout almost the entire volume. We encapsulate these average results in a parameterized form appropriate for when an approximate treatment of the effects of dumpiness is desired. However, the large point-to-point variance in this behavior suggests that uncertainties may arise when using mean values to model particular lines of sight in detail. Ideally, these new results would be used in conjunction with established results for homogeneous clouds in order to span a range of behavior that arises due to cloud inhomogeneities. We briefly explore the importance of the adopted dust properties, characterized by the selective extinction R sub(V) and the scattering parameter g. We find that the UV field is considerably less sensitive to these dust properties in clumpy clouds, emphasizing the preeminence of geometry.
We provide simple polynomial fits to the X-ray photoelectric cross-sections (0.03 keV < E < 10 keV) for mixtures of gas and dust found in protoplanetary disks. Using the solar elemental abundances of ...Asplund et al., we treat the gas and dust components separately, facilitating the further exploration of evolutionary processes such as grain settling and gain growth. We find that blanketing due to advanced grain growth (a{sub max} > 1 {mu}m) can reduce the X-ray opacity of dust appreciably at E{sub X} {approx} 1 keV, coincident with the peak of typical T Tauri X-ray spectra. However, the reduction of dust opacity by dust settling, which is known to occur in protoplanetary disks, is probably a more significant effect. The absorption of 1-10 keV X-rays is dominated by gas opacity once the dust abundance has been reduced to about 1% of its diffuse interstellar value. The gas disk establishes a floor to the opacity at which point X-ray transport becomes insensitive to further dust evolution. Our choice of fitting function follows that of Morrison and McCammon, providing a degree of backward compatibility.
A variant of the influenza virus NWS/G70C has been generated which has decreased sensitivityin vitroto the neuraminidase-specific inhibitor, 4-guanidino-Neu5Ac2en. The virus is 1000-fold less ...sensitive to the 4-guanidino-Neu5Ac2en in a plaque assay, but only 10-fold less sensitive to 4-amino-Neu5Ac2en. In an enzyme inhibition assay 250-fold more drug was needed to achieve inhibition comparable to that observed with the parent virus. In contrast to the plaque assay, the virus was fully sensitive to 4-amino-Neu5Ac2en in the enzyme inhibition assay. Kinetic analysis of 4-guanidino-Neu5Ac2en binding demonstrated that the variant no longer exhibited the slow binding characteristic seen with the parent and other influenza viruses and inhibition by Neu5Ac2en was also decreased. However, binding to 4-amino-Neu5Ac2en remained the same as the parent. Sequence analysis of this virus revealed a mutation at a previously conserved site in the enzyme active site of the neuraminidase, Glu 119 to Gly. Crystallographic analysis of the mutant neuraminidase with and without bound inhibitor confirmed this mutation and suggested that the reduced affinity for the 4-guanidino-Neu5Ac2en derives partly from the loss of a stabilizing interaction between the guanidino moiety and the carboxylate at residue 119, and partly from alterations to the solvent structure of the active site.
We have calculated the radiation field, dust grain temperatures, and far- infrared emissivity of numerical models of turbulent molecular clouds. When compared to a uniform cloud of the same mean ...optical depth, most of the volume inside the turbulent cloud is brighter, but most of the mass is darker. There is little mean attenuation from center to edge, and clumping causes the radiation field to be somewhat bluer. There is also a large dispersion, typically by a few orders of magnitude, of all quantities relative to their means. However, despite the scatter, the 850 mu m emission maps are well correlated with surface density. The fraction of mass as a function of intensity can be reproduced by a simple hierarchical model of density structure.
Attention bias describes the differential allocation of attention towards one stimulus compared to others. In humans, this bias can be mediated by the observer's affective state and is implicated in ...the onset and maintenance of affective disorders such as anxiety. Affect-driven attention biases (ADABs) have also been identified in a few other species. Here, we review the literature on ADABs in animals and discuss their utility as welfare indicators. Despite a limited research effort, several studies have found that negative affective states modulate attention to negative (i.e., threatening) cues. ADABs influenced by positive-valence states have also been documented in animals. We discuss methods for measuring ADAB and conclude that looking time, dot-probe, and emotional spatial cueing paradigms are particularly promising. Research is needed to test them with a wider range of species, investigate attentional scope as an indicator of affect, and explore the possible causative role of attention biases in determining animal wellbeing. Finally, we argue that ADABs might not be best-utilized as indicators of general valence, but instead to reveal specific emotions, motivations, aversions, and preferences. Paying attention to the human literature could facilitate these advances.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Robust methods to assess nonhuman animal emotion are essential for ensuring good welfare in captivity. Cognitive bias measures such as the judgment bias task have recently emerged as promising tools ...to assess animal emotion. The simple design and objective response measures make judgment bias tasks suitable for use across species and contexts. In reviewing 64 studies published to date, it emerged that (a) judgment biases have been measured in a number of mammals and birds and an invertebrate; (b) no study has tested judgment bias in any species of fish, amphibian, or reptile; and (c) no study has yet investigated judgment bias in a zoo or aquarium. This article proposes that judgment bias measures are highly suitable for use with these understudied taxa and can provide new insight into welfare in endangered species housed in zoos and aquariums, where poor welfare impacts breeding success and, ultimately, species survival. The article includes a “how-to” guide to designing judgment bias tests with recommendations for working with currently neglected “exotics” including fishes, amphibians, and reptiles.
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