1,992 research outputs found
Insect adhesion on rough surfaces: analysis of adhesive contact of smooth and hairy pads on transparent microstructured substrates.
Insect climbing footpads are able to adhere to rough surfaces, but the details of this capability are still unclear. To overcome experimental limitations of randomly rough, opaque surfaces, we fabricated transparent test substrates containing square arrays of 1.4 µm diameter pillars, with variable height (0.5 and 1.4 µm) and spacing (from 3 to 22 µm). Smooth pads of cockroaches (Nauphoeta cinerea) made partial contact (limited to the tops of the structures) for the two densest arrays of tall pillars, but full contact (touching the substrate in between pillars) for larger spacings. The transition from partial to full contact was accompanied by a sharp increase in shear forces. Tests on hairy pads of dock beetles (Gastrophysa viridula) showed that setae adhered between pillars for larger spacings, but pads were equally unable to make full contact on the densest arrays. The beetles' shear forces similarly decreased for denser arrays, but also for short pillars and with a more gradual transition. These observations can be explained by simple contact models derived for soft uniform materials (smooth pads) or thin flat plates (hairy-pad spatulae). Our results show that microstructured substrates are powerful tools to reveal adaptations of natural adhesives for rough surfaces
Microheterogeneity of Type II cAMP-Dependent Protein Kinase in Various Mammalian Species and Tissues
Excluding autophosphorylated species, at least six forms of the regulatory subunit of type II cAMP-dependent protein kinase (R(II)) from various mammalian tissues were identified by sodium dodecyl sulfate (SDS) gel electrophoresis of purified samples and of crude preparations photoaffinity labeled with 8-azido[32P] cAMP and by gel filtration. After autophosphorylation some heart R(II) forms termed type IIA (bovine, porcine, equine, and dog) shifted to a more slowly migrating band on SDS gels while others termed type IIB (rat, guinea pig, rabbit, and monkey) did not detectably shift. Both subclasses of R(II) exhibited variation in apparent M(r) on SDS gels. Bovine and porcine heart nonautophosphorylated R(II) had M(r) 56,000 and the autophosphorylated R(II) had M(r) 58,000, while dog and equine heart R(II) had M(r) 54,000 and 56,000 for these bands, respectively. Rat heart R(II) had M(r) 56,000 while rabbit and guinea pig heart R(II) had M(r) 52,000. More than one R(II) was found in different tissues of the same species. Rabbit skeletal muscle contained a M(r) 56,000 IIB form. Bovine lung contained almost equal amounts of a IIA form apparently identical to that of bovine heart and a M(r) 52,000 IIB form similar to that which predominated in bovine brain. Rat adipose tissue, brain, and monkey heart contained predominantly a M(r) 51,000 IIB form. The rat liver M(r) 56,000 IIB form chromatographed differently from all other R(II) tested by gel filtration. Several lines of evidence indicated that the various forms of R(II) were not derived from one another through proteolysis or other processes. Each of the type II forms rapidly incorporated 0.3-1.0 mol of 32P per mol of subunit when incubated with [γ-32P]ATP and C subunit. Four of the forms tested were similar in the cAMP concentration dependence for activation of their corresponding holoenzymes and inhibited C subunit about equally. Each exhibited two components of [3H]cAMP dissociation, indicating two intrachain cAMP-binding sites, and the dissociation rates for the respective sites, and the dissociation rates for the respective sites were similar
Insect adhesion on rough surfaces: analysis of adhesive contact of smooth and hairy pads on transparent microstructured substrates.
Insect climbing footpads are able to adhere to rough surfaces, but the details of this capability are still unclear. To overcome experimental limitations of randomly rough, opaque surfaces, we fabricated transparent test substrates containing square arrays of 1.4 µm diameter pillars, with variable height (0.5 and 1.4 µm) and spacing (from 3 to 22 µm). Smooth pads of cockroaches (Nauphoeta cinerea) made partial contact (limited to the tops of the structures) for the two densest arrays of tall pillars, but full contact (touching the substrate in between pillars) for larger spacings. The transition from partial to full contact was accompanied by a sharp increase in shear forces. Tests on hairy pads of dock beetles (Gastrophysa viridula) showed that setae adhered between pillars for larger spacings, but pads were equally unable to make full contact on the densest arrays. The beetles' shear forces similarly decreased for denser arrays, but also for short pillars and with a more gradual transition. These observations can be explained by simple contact models derived for soft uniform materials (smooth pads) or thin flat plates (hairy-pad spatulae). Our results show that microstructured substrates are powerful tools to reveal adaptations of natural adhesives for rough surfaces
Mobile device use when caring for children 0-5 years: A naturalistic playground study
Issue addressed: Over the past decade, mobile device use has increased significantly. Adults are now using their mobile device whilst undertaking a range of work and social activities. This naturalistic study aimed to understand parents/carers' use of mobile devices and their associated beliefs about mobile device use whilst caring for children aged five and younger in playgrounds. Methods: A mixed methods approach was used to collect quantitative and qualitative data from parents/carers. Data were collected by observations (n = 50) and interviews (n = 25) in playgrounds on the North Coast of New South Wales, Australia. Results: Of the 50 observed parents/carers, 76% (n = 38) used their mobile device, with usage time extending to 17.2 minutes of the 20 minute observation period. Text-/type-related mobile device use was most often used (69.6%), followed by voice-related (23.7%) and camera-related mobile device use (6.7%). The 25 interviewed parents/carers beliefs on mobile device use were centred on three themes: diversity of mobile device use, child relationships and mobile device use and the physical environment and mobile device use. Conclusion: This study adds to the limited research into parent/carer mobile device use, which has become an integral part of peoples' lifestyle. However, research is required to better understand how parent/carer mobile device use may impact on child supervision and interaction. So what?: Mobile device use is increasing. We need to better understand its public health impact
Pre-Release Consumption of Methyl Eugenol Increases the Mating Competitiveness of Sterile Males of the Oriental Fruit Fly, Bactrocera dorsalis, in Large Field Enclosures
The sterile insect technique may be implemented to control populations of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), when environmental concerns preclude widespread use of chemical attractants or toxicants. The goal of the present study was to evaluate whether the mating competitiveness of sterile B. dorsalis males could be increased via pre-release feeding on methyl eugenol. Males of the oriental fruit fly are strongly attracted to this plant-borne compound, which they ingest and use in the synthesis of the sex pheromone. Previous studies conducted in the laboratory and small field-cages have shown that males given methyl eugenol produce a more attractive pheromone for females and have a higher mating success rate than males denied methyl eugenol. Here, levels of egg sterility were compared following the release of wild-like flies and either methyl eugenol-fed (treated) or methyl eugenol-deprived (control) sterile males in large field enclosures at four over flooding ratios ranging from 5:1 to 60:1 (sterile: wild-like males). Treated sterile males were fed methyl eugenol for 1–4 h (depending on the over flooding ratio tested) 3 d prior to release. Eggs were dissected from introduced fruits (apples), incubated in the laboratory, and scored for hatch rate. The effect of methyl eugenol was most pronounced at lower over flooding ratios. At the 5:1 and 10:1 over flooding ratios, the level of egg sterility observed for treated, sterile males was significantly greater than that observed for control, sterile males. In addition, the incidence of egg sterility reported for treated sterile males at these lower over flooding ratios was similar to that noted for treated or control sterile males at the 30:1 or 60:1 over flooding ratios. This latter result, in particular, suggests that pre-release feeding on methyl eugenol allows for a reduction in the number of sterile flies that are produced and released, thus increasing the cost-effectiveness of the sterile insect technique
A persistence landscapes toolbox for topological statistics
Topological data analysis provides a multiscale description of the geometry
and topology of quantitative data. The persistence landscape is a topological
summary that can be easily combined with tools from statistics and machine
learning. We give efficient algorithms for calculating persistence landscapes,
their averages, and distances between such averages. We discuss an
implementation of these algorithms and some related procedures. These are
intended to facilitate the combination of statistics and machine learning with
topological data analysis. We present an experiment showing that the
low-dimensional persistence landscapes of points sampled from spheres (and
boxes) of varying dimensions differ.Comment: 24 page
Episodic Post-Shock Dust Formation in the Colliding Winds of Eta Carinae
Eta Carinae shows broad peaks in near-infrared (IR) JHKL photometry, roughly
correlated with times of periastron passage in the eccentric binary system.
After correcting for secular changes attributed to reduced extinction from the
thinning Homunculus Nebula, these peaks have IR spectral energy distributions
(SEDs) consistent with emission from hot dust at 1400-1700 K. The excess SEDs
are clearly inconsistent, however, with the excess being entirely due to
free-free wind or photospheric emission. One must conclude, therefore, that the
broad near-IR peaks associated with Eta Carinae's 5.5 yr variability are due to
thermal emission from hot dust. I propose that this transient hot dust results
from episodic formation of grains within compressed post-shock zones of the
colliding winds, analogous to the episodic dust formation in Wolf-Rayet binary
systems like WR140 or the post-shock dust formation seen in some supernovae
like SN2006jc. This dust formation in Eta Carinae seems to occur preferentially
near and after periastron passage; near-IR excess emission then fades as the
new dust disperses and cools. With the high grain temperatures and Eta Car's
C-poor abundances, the grains are probably composed of corundum or similar
species that condense at high temperatures, rather than silicates or graphite.
Episodic dust formation in Eta Car's colliding winds significantly impacts our
understanding of the system, and several observable consequences are discussed.Comment: MNRAS accepted; 8 pages, 5 figs, 2 color fig
Experiments on subcooled flow boiling in I.C. engine-like conditions at low flow velocities
[EN] Subcooled boiling flow is specially attractive for engine cooling system design, as no essential changes in its architecture are required while it is still possible to take advantage of the highest rates of heat transfer associated with nucleate boiling, mostly at high engine loads. In this paper, experiments on subcooled boiling flow in representative temperature conditions were conducted with a usual engine coolant in the low velocity range, for which little information is available, even if it may be relevant when advanced thermal management strategies are used. The results were analyzed by comparison with a reference Chen-type model which provided reasonable results for relatively low wall temperatures, but with noticeable discrepancies at higher wall temperatures. Analysis of the deviations observed indicated a significant influence of the Prandtl number on the suppression factor, and the inclusion into the model of a first estimate of this effect produced a noticeable improvement in its results, thus suggesting that one such modified additive model may be useful for practical engine cooling applications. (C) 2013 Elsevier Inc. All rights reserved.This work has been supported by Ministerio de Ciencia e Innovacion through Grant TRA2010-16205. O. Cornejo is indebted to Senacyt Panama for their support.Torregrosa, AJ.; Broatch, A.; Olmeda, P.; Cornejo, O. (2014). Experiments on subcooled flow boiling in I.C. engine-like conditions at low flow velocities. Experimental Thermal and Fluid Science. 52:347-354. https://doi.org/10.1016/j.expthermflusci.2013.10.004S3473545
The persistence landscape and some of its properties
Persistence landscapes map persistence diagrams into a function space, which
may often be taken to be a Banach space or even a Hilbert space. In the latter
case, it is a feature map and there is an associated kernel. The main advantage
of this summary is that it allows one to apply tools from statistics and
machine learning. Furthermore, the mapping from persistence diagrams to
persistence landscapes is stable and invertible. We introduce a weighted
version of the persistence landscape and define a one-parameter family of
Poisson-weighted persistence landscape kernels that may be useful for learning.
We also demonstrate some additional properties of the persistence landscape.
First, the persistence landscape may be viewed as a tropical rational function.
Second, in many cases it is possible to exactly reconstruct all of the
component persistence diagrams from an average persistence landscape. It
follows that the persistence landscape kernel is characteristic for certain
generic empirical measures. Finally, the persistence landscape distance may be
arbitrarily small compared to the interleaving distance.Comment: 18 pages, to appear in the Proceedings of the 2018 Abel Symposiu
Energy transport, overshoot, and mixing in the atmospheres of M-type main- and pre-main-sequence objects
We constructed hydrodynamical model atmospheres for mid M-type main-, as well
as pre-main-sequence (PMS) objects. Despite the complex chemistry encountered
in these cool atmospheres a reasonably accurate representation of the radiative
transfer is possible, even in the context of time-dependent and
three-dimensional models. The models provide detailed information about the
morphology of M-type granulation and statistical properties of the convective
surface flows. In particular, we determined the efficiency of the convective
energy transport, and the efficiency of mixing by convective overshoot. The
convective transport efficiency was expressed in terms of an equivalent
mixing-length parameter alpha in the formulation of mixing-length theory (MLT)
given by Mihalas (1978). Alpha amounts to values around 2 for matching the
entropy of the deep, adiabatically stratified regions of the convective
envelope, and lies between 2.5 and 3.0 for matching the thermal structure of
the deep photosphere. For current spectral analysis of PMS objects this implies
that MLT models based on alpha=2.0 overestimate the effective temperature by
100 K and surface gravities by 0.25 dex. The average thermal structure of the
formally convectively stable layers is little affected by convective overshoot
and wave heating, i.e., stays close to radiative equilibrium conditions. Our
models suggest that the rate of mixing by convective overshoot declines
exponentially with geometrical distance to the Schwarzschild stability
boundary. It increases at given effective temperature with decreasing
gravitational acceleration.Comment: 17 pages, 23 figures, accepted for publication in A&
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