Harbor seals (Phoca vitulina) often live in dark and turbid waters, where their mystacial vibrissae, or whiskers, play an important role in orientation. Besides detecting and discriminating objects ...by direct touch, harbor seals use their whiskers to analyze water movements, for example those generated by prey fish or by conspecifics. Even the weak water movements left behind by objects that have passed by earlier can be sensed and followed accurately (hydrodynamic trail following). While scanning the water for these hydrodynamic signals at a swimming speed in the order of meters per second, the seal keeps its long and flexible whiskers in an abducted position, largely perpendicular to the swimming direction. Remarkably, the whiskers of harbor seals possess a specialized undulated surface structure, the function of which was, up to now, unknown. Here, we show that this structure effectively changes the vortex street behind the whiskers and reduces the vibrations that would otherwise be induced by the shedding of vortices from the whiskers (vortex-induced vibrations). Using force measurements, flow measurements and numerical simulations, we find that the dynamic forces on harbor seal whiskers are, by at least an order of magnitude, lower than those on sea lion (Zalophus californianus) whiskers, which do not share the undulated structure. The results are discussed in the light of pinniped sensory biology and potential biomimetic applications.
Mutation timing in a spatial model of evolution Foo, Jasmine; Leder, Kevin; Schweinsberg, Jason
Stochastic processes and their applications,
October 2020, 2020-10-00, Letnik:
130, Številka:
10
Journal Article
Recenzirano
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Motivated by models of cancer formation in which cells need to acquire k mutations to become cancerous, we consider a spatial population model in which the population is represented by the ...d-dimensional torus of side length L. Initially, no sites have mutations, but sites with i−1 mutations acquire an ith mutation at rate μi per unit area. Mutations spread to neighboring sites at rate α, so that t time units after a mutation, the region of individuals that have acquired the mutation will be a ball of radius αt. We calculate, for some ranges of the parameter values, the asymptotic distribution of the time required for some individual to acquire k mutations. Our results, which build on previous work of Durrett, Foo, and Leder, are essentially complete when k=2 and when μi=μ for all i.
For externally fertilising organisms in the aquatic environment, the abiotic fertilisation medium can be a strong selecting force. Among bony fishes, sperm are adapted to function in a narrow ...salinity range. A notable exception is the family Gobiidae, where several species reproduce across a wide salinity range. The family also contains several wide-spread invasive species. To better understand how these fishes tolerate such varying conditions, we measured sperm performance in relation to salinity from a freshwater and a brackish population within their ancestral Ponto-Caspian region of the round goby, Neogobius melanostomus. These two ancestral populations were then compared to nine additional invaded sites across northern Europe, both in terms of their sperm traits and by using genomic SNP markers. Our results show clear patterns of ancestral adaptations to freshwater and brackish salinities in their sperm performance. Population genomic analyses show that the ancestral ecotypes have generally established themselves in environments that fit their sperm adaptations. Sites close to ports with intense shipping show that both outbreeding and admixture can affect the sperm performance of a population in a given salinity. Rapid adaptation to local conditions is also supported at some sites. Historical and contemporary evolution in the traits of the round goby sperm cells is tightly linked to the population and seascape genomics as well as biogeographic processes in these invasive fishes. Since the risk of a population establishing in an area is related to the genotype by environment match, port connectivity and the ancestry of the round goby population can likely be useful for predicting the species spread.
•A mathematical model is compared to radiograph data with quite similar results.•Radiograph data with liquid pools and morphological types within ingot are stated.•Model able to predict dynamic of ...crystallization front during VAR is presented.•Fundamental principles of GV-map construction for VT3-1 alloy are considered.
We consider the crystallization morphology formation of VT3-1 (Ti-6.5Al-2.5Mo-1.5Cr-0.5Fe-0.3Si) titanium alloy during vacuum arc remelting (VAR). Combining a mathematical model and data acquired from radiograph experiments, unknown model parameters are determined. A refined mathematical model is compared to radiograph data with quite similar results. Using a ”tuned” model, important solidification characteristics, such as the temperature gradient G at the solidification front, and its velocity V are calculated. An industrial ingot remelting trajectory is presented in GV-space using a GV-map. The essential importance of the GV-map to the VAR process is demonstrated.
Fibroblast growth factor 23 (FGF23) promotes phosphaturia and suppresses 1,25‐dihydroxyvitamin D 1,25(OH)2D production. PTH also promotes phosphaturia, but, in contrast, stimulates 1,25(OH)2D ...production. The relationship between FGF23 and PTH is unclear, and the acute effect of pharmacologically dosed PTH on FGF23 secretion is unknown. Twenty healthy men were infused with human PTH(1‐34) hPTH(1‐34) at 44 ng/kg/h for 24 h. Compared with baseline, FGF23, 1,25(OH)2D, ionized calcium (iCa), and serum N‐telopeptide (NTX) increased significantly over the 18‐h hPTH(1‐34) infusion (p < 0.0001), whereas serum phosphate (PO4) transiently increased and then returned to baseline. FGF23 increased from 35 ± 10 pg/ml at baseline to 53 ± 20 pg/ml at 18 h (p = 0.0002); 1,25(OH)2D increased from 36 ± 16 pg/ml at baseline to 80 ± 33 pg/ml at 18 h (p < 0.0001); iCa increased from 1.23 ± 0.03 mM at baseline to 1.46 ± 0.05 mM at hour 18 (p < 0.0001); and NTX increased from 17 ± 4 nM BCE at baseline to 28 ± 8 nM BCE at peak (p < 0.0001). PO4 was 3.3 ± 0.6 mg/dl at baseline, transiently rose to 3.7 ± 0.4 mg/dl at hour 6 (p = 0.016), and then returned to 3.4 ± 0.5 mg/dl at hour 12 (p = 0.651). hPTH(1‐34) infusion increases endogenous 1,25(OH)2D and FGF23 within 18 h in healthy men. Whereas it is possible that the rise in PO4 contributed to the observed increase in FGF23, the increase in 1,25(OH)2D was more substantial and longer sustained than the change in serum phosphate. Given prior data that suggest that neither PTH nor calcium stimulate FGF23 secretion, these data support the assertion that 1,25(OH)2D is a potent physiologic stimulator of FGF23 secretion.
When an individual participates in empirical studies involving the visual arts, they most often are presented with a stream of images, shown on a computer, depicting reproductions of artworks by ...respected artists but which are often not known to the viewer. While art can of course be shown in
-e.g., in the museum-this laboratory paradigm has become our go-to basis for assessing interaction, and, often in conjunction with some means of rating, for assessing evaluative, emotional, cognitive, and even neurophysiological response. However, the question is rarely asked: Do participants actually believe that every image that they are viewing is indeed "Art"? Relatedly, how does this evaluation relate to aesthetic appreciation, and do the answers to these questions vary in accordance with different strategies and interpersonal differences? In this paper, we consider the spontaneous classification of digital reproductions as art or not art. Participants viewed a range of image types-Abstract, Hyperrealistic, Poorly Executed paintings, Readymade sculptures, as well as Renaissance and Baroque paintings. They classified these as "art" or "not art" using both binary and analog scales, and also assessed for liking. Almost universally, individuals did not find all items within a class to be "art," nor did all participants agree on the arthood status for any one item. Art classification in turn showed a significant positive correlation with liking. Whether an object was classified as art moreover correlated with specific personality variables, tastes, and decision strategies. The impact of these findings is discussed for selection/assessment of participants and for better understanding the basis of findings in past and future empirical art research.
The overlap operator is a lattice discretization of the Dirac operator of quantum chromodynamics (QCD), the fundamental physical theory of the strong interaction between the quarks. As opposed to ...other discretizations, it preserves the important physical property of chiral symmetry, at the expense of requiring much more effort when solving systems posed with this operator. We present a preconditioning technique based on another lattice discretization, the Wilson-Dirac operator. The mathematical analysis precisely describes the effect of this preconditioning strategy in the case that the Wilson-Dirac operator is normal. Although this is not exactly the case in realistic settings, we show that current smearing techniques indeed drive the Wilson-Dirac operator towards normality, thus providing motivation for why our preconditioner works well in practice. Results of numerical experiments in physically relevant settings show that our preconditioning yields accelerations of more than an order of magnitude compared to unpreconditioned solvers.
Creativity is a compelling yet elusive phenomenon, especially when manifested in visual art, where its evaluation is often a subjective and complex process. Understanding how individuals judge ...creativity in visual art is a particularly intriguing question. Conventional linear approaches often fail to capture the intricate nature of human behavior underlying such judgments. Therefore, in this study, we employed interpretable machine learning to probe complex associations between 17 subjective art-attributes and creativity judgments across a diverse range of artworks. A cohort of 78 non-art expert participants assessed 54 artworks varying in styles and motifs. The applied Random Forests regressor models accounted for 30% of the variability in creativity judgments given our set of art-attributes. Our analyses revealed symbolism, emotionality, and imaginativeness as the primary attributes influencing creativity judgments. Abstractness, valence, and complexity also had an impact, albeit to a lesser degree. Notably, we observed non-linearity in the relationship between art-attribute scores and creativity judgments, indicating that changes in art-attributes did not consistently correspond to changes in creativity judgments. Employing statistical learning, this investigation presents the first attribute-integrating quantitative model of factors that contribute to creativity judgments in visual art among novice raters. Our research represents a significant stride forward building the groundwork for first causal models for future investigations in art and creativity research and offering implications for diverse practical applications. Beyond enhancing comprehension of the intricate interplay and specificity of attributes used in evaluating creativity, this work introduces machine learning as an innovative approach in the field of subjective judgment.
Measuring stress in animals is important in many ecological, zoological and veterinary research settings. A common method is to measure plasma levels of glucocorticoid hormones (cortisol, ...corticosterone, hereafter CORT). Over the past decade, an alternative method has become widely popular: assessing leucocyte profiles; in other words, the heterophil‐to‐lymphocyte ratio (H/L) in birds and reptiles or the neutrophil‐to‐lymphocyte ratio (N/L) in mammals, amphibians and fish. Recent studies have shown that although both indices reliably change after acute stress, they are not always correlated at baseline, and thus are not interchangeable. This lack of correlation has led to some confusion about which of these two measures is “better”; in other words, more biologically relevant and a truer readout of stress.
In this review, we first document the dramatic expansion of the use of leucocyte profiles to assess stress over the past decade. We then review published evidence that may explain the discrepancies between leucocyte profiles and plasma CORT. We argue that these discrepancies stem from the nature of the stress reaction and the role of corticosterone (or cortisol) versus leucocytes during the stress response.
The differing roles of the two responses translate to differences in the timing of each, which is important for researchers studying either acute or chronic stress. Although plasma glucocorticoids rise within minutes of the onset of acute stress and return to baseline within 1 or 2 hr after the stressor passes, H/L or N/L ratios remain low for at least 30–60 min or sometimes more.
The temporal nature of these metrics differs also in the context of long‐term chronic stress. The glucocorticoid response wanes in repeatedly stressed animals, or those exposed to chronic environmental stress, which can often (but not always) lead to low baseline levels and more typically, an attenuated acute stress response. Meanwhile, H/L or N/L ratios appear to remain high under the same conditions.
Understanding the temporal differences in the responses should help researchers decide which metric is the better method in their particular study, or whether both would be useful for elucidating different elements of the stress response.
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