2,387 research outputs found
Acoustic suppression of the coffee-ring effect
We study the influence of acoustic fields on the evaporative self-assembly of solute particles suspended inside sessile droplets of complex fluids. The self-assembly process often results in an undesirable ring-like heterogeneous residue, a phenomenon known as the coffee-ring effect. Here we show that this ring-like self-assembly can be controlled acoustically to form homogeneous disc-like or concentrated spot-like residues. The principle of our method lies in the formation of dynamic patterns of particles in acoustically excited droplets, which inhibits the evaporation-driven convective transport of particles towards the contact line. We elucidate the mechanisms of this pattern formation and also obtain conditions for the suppression of the coffee-ring effect. Our results provide a more general solution to suppress the coffee-ring effect without any physiochemical modification of the fluids, the particles or the surface, thus potentially useful in a broad range of industrial and analytical applications that require homogenous solute depositions
Experiential Factors Affect Red and Blue Preferences in Neonatal Chickens (Gallus gallus)
White leghorn chickens (Gallus Gallus) were isolated and reared in either white, half red and half blue, red, or blue cages, and at 60 hrs. and 120 hrs. were given a preference test for either a red or blue stationary object. Chicks housed in white cages were exposed to white throughout the experiment, and chicks housed in half red and half blue were exposed to red and blue in the same manner. Subjects housed in red cages for the first 60 hrs. were reversed to blue cages for the second 60 hrs. and subjects initially housed in blue cages were reversed to red cages. Subjects exposed to white, red and blue or red, showed a preference for red at 60 hrs. while subjects initially exposed to blue showed a tendency to prefer blue. At 120 hrs. subjects exposed to white showed no preference, while the subjects exposed to red and blue continued to display a red preference. Subjects initially exposed to red and reversed to blue showed no preference but subjects reversed from blue to red showed a red preference. This suggests that color preferences in chicks may be affected by an interaction between the initial attractiveness of a color and the amount of experience with that color at an early age
Recent advances in the treatment of premature ejaculation
Premature ejaculation (PE) is the most common sexual problem affecting men. It can affect men at all ages and has a serious impact on the quality of life for men and their partners. Currently there are no pharmaceutical agents approved for use in the UK, and so all drugs used for this condition are off label. Behavioral therapy has been used to treat PE, but the results are not durable once therapy has been concluded. Several topical therapies have been used including severance-secret (SS) cream, lignocaine spray, lidocaine-prilocaine cream and lidocaine-prilocaine spray (TEMPE). There has been recent interest in the selective serotonin reuptake inhibitors (SSRIs) for the treatment of PE, due to the fact that one of their common side effects is delayed ejaculation. Currently used SSRIs have several non-sexual side effects and long half lives, therefore there has been interest in developing a short acting, efficacious SSRI that can be used on-demand for PE. Dapoxetine has been recently evaluated for the treatment of PE by several groups, and results so far appear promising
Plant extract efficacy on mosquito mortality: preliminary studies on the effect of Ailanthus altissima extract on adult Aedes aegypti and Culex quinquefasciatus
Abstract
Due to the negative environmental impact and resistance to synthetic insecticides, the development of biological control has increased significantly over the past half century with the potential of plant extracts only recently attracting attention. The purpose of this preliminary study was to examine the potential of Ailanthus altissima extract as a botanical insecticide on adult mosquitoes. Two species of mosquitoes (Aedes aegypti and Culex quinquefasciatus) and a non-target lepidopteran species, Painted Lady butterfly (Vanessa cardui) were treated with A. altissima extract from new, mature, and senesced leaflets using serial dilutions (0, 25, 50, 75, 100%) of extract via two application methods (aerosol and sugar feeding). We found that application method and leaf age had significant effects on mosquito mortality at high concentrations. These findings indicate that while mortality was not significantly high compared to commercial products, there may be potential to use an invasive plant extract as a bio-control tool for mosquito vectors of human disease pathogens
Casimir Force between a Dielectric Sphere and a Wall: A Model for Amplification of Vacuum Fluctuations
The interaction between a polarizable particle and a reflecting wall is
examined. A macroscopic approach is adopted in which the averaged force is
computed from the Maxwell stress tensor. The particular case of a perfectly
reflecting wall and a sphere with a dielectric function given by the Drude
model is examined in detail. It is found that the force can be expressed as the
sum of a monotonically decaying function of position and of an oscillatory
piece. At large separations, the oscillatory piece is the dominant
contribution, and is much larger than the Casimir-Polder interaction that
arises in the limit that the sphere is a perfect conductor. It is argued that
this enhancement of the force can be interpreted in terms of the frequency
spectrum of vacuum fluctuations. In the limit of a perfectly conducting sphere,
there are cancellations between different parts of the spectrum which no longer
occur as completely in the case of a sphere with frequency dependent
polarizability. Estimates of the magnitude of the oscillatory component of the
force suggest that it may be large enough to be observable.Comment: 18pp, LaTex, 7 figures, uses epsf. Several minor errors corrected,
additional comments added in the final two sections, and references update
Incidence and clinical signs of owner-reported equine laminitis in a cohort of horses and ponies in Great Britain
Neurons Responsive to Global Visual Motion Have Unique Tuning Properties in Hummingbirds
Neurons in animal visual systems that respond to
global optic flow exhibit selectivity for motion direction and/or velocity. The avian lentiformis mesencephali (LM), known in mammals as the nucleus of the
optic tract (NOT), is a key nucleus for global motion
processing [1–4]. In all animals tested, it has been
found that the majority of LM and NOT neurons
are tuned to temporo-nasal (back-to-front) motion
[4–11]. Moreover, the monocular gain of the optokinetic response is higher in this direction, compared
to naso-temporal (front-to-back) motion [12, 13].
Hummingbirds are sensitive to small visual perturbations while hovering, and they drift to compensate for
optic flow in all directions [14]. Interestingly, the LM,
but not other visual nuclei, is hypertrophied in hummingbirds relative to other birds [15], which suggests
enhanced perception of global visual motion. Using
extracellular recording techniques, we found that
there is a uniform distribution of preferred directions
in the LM in Anna’s hummingbirds, whereas zebra
finch and pigeon LM populations, as in other tetrapods, show a strong bias toward temporo-nasal motion. Furthermore, LM and NOT neurons are generally
classified as tuned to ‘‘fast’’ or ‘‘slow’’ motion [10, 16,
17], and we predicted that most neurons would be
tuned to slow visual motion as an adaptation for
slow hovering. However, we found the opposite
result: most hummingbird LM neurons are tuned to
fast pattern velocities, compared to zebra finches
and pigeons. Collectively, these results suggest a
role in rapid responses during hovering, as well as
in velocity control and collision avoidance during forward flight of hummingbirds
Pretectal projections to the oculomotor cerebellum in hummingbirds ( Calypte anna ), zebra finches ( Taeniopygia guttata ), and pigeons ( Columba livia )
In birds, optic flow is processed by a retinal‐recipient nucleus in the pretectum, the nucleus lentiformis mesencephali (LM), which then projects to the cerebellum, a key site for sensorimotor integration. Previous studies have shown that the LM is hypertrophied in hummingbirds, and that LM cell response properties differ between hummingbirds and other birds. Given these differences in anatomy and physiology, we ask here if there are also species differences in the connectivity of the LM. The LM is separated into lateral and medial subdivisions, which project to the oculomotor cerebellum and the vestibulocerebellum. In pigeons, the projection to the vestibulocerebellum largely arises from the lateral LM; the projection to the oculomotor cerebellum largely arises from the medial LM. Here, using retrograde tracing, we demonstrate differences in the distribution of projections in these pathways between Anna's hummingbirds (Calypte anna ), zebra finches (Taeniopygia guttata ), and pigeons (Columba livia ). In all three species, the projections to the vestibulocerebellum were largely from lateral LM. In contrast, projections to the oculomotor cerebellum in hummingbirds and zebra finches do not originate in the medial LM (as in pigeons) but instead largely arise from pretectal structures just medial, the nucleus laminaris precommissuralis and nucleus principalis precommissuralis. These species differences in projection patterns provide further evidence that optic flow circuits differ among bird species with distinct modes of fligh
The Asymptotic Giant Branches of GCs: Selective Entry Only
The handful of available observations of AGB stars in Galactic Globular
Clusters suggest that the GC AGB populations are dominated by cyanogen-weak
stars. This contrasts strongly with the distributions in the RGB (and other)
populations, which generally show a 50:50 bimodality in CN band strength. If it
is true that the AGB populations show very different distributions then it
presents a serious problem for low mass stellar evolution theory, since such a
surface abundance change going from the RGB to AGB is not predicted by stellar
models. However this is only a tentative conclusion, since it is based on very
small AGB sample sizes. To test whether this problem really exists we have
carried out an observational campaign specifically targeting AGB stars in GCs.
We have obtained medium resolution spectra for about 250 AGB stars across 9
Galactic GCs using the multi-object spectrograph on the AAT (2df/AAOmega). We
present some of the preliminary findings of the study for the second parameter
trio of GCs: NGC 288, NGC 362 and NGC 1851. The results indeed show that there
is a deficiency of stars with strong CN bands on the AGB. To confirm that this
phenomenon is robust and not just confined to CN band strengths and their
vagaries, we have made observations using FLAMES/VLT to measure elemental
abundances for NGC 6752.We present some initial results from this study also.
Our sodium abundance results show conclusively that only a subset of stars in
GCs experience the AGB phase of evolution. This is the first direct, concrete
confirmation of the phenomenon.Comment: 4 pages, to appear in conference proceedings of "Reading the book of
globular clusters with the lens of stellar evolution", Rome, 26-28 November
201
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