1,593 research outputs found
The Effect of Impact Angle on the Secondary Droplets at High Impact Velocity
This study focuses on the secondary droplets ejected during splashing at different impact angles. We consider the
theory of Riboux & Gordillo [1], which attributes the generation of secondary droplets to a lift force that acts on the
spreading lamella, and propose a new approach to handle the oblique impact. This approach is based on previous
studies on the lamella formed by impinging jets, where the impacting flow is distributed in the azimuthal direction.
To validate the proposed method, we used a flywheel experiment and captured the secondary droplets that are
ejected at Weber number larger than 4500 at three different impact angles. In our experimental setup, the droplets
were formed by a droplet generator and then let to fall freely due to gravity until impacting the substrate, which
was mounted on a flywheel. The small and fast secondary droplets were captured using a shadowgraph technique
together with a high-resolution camera and Nd:YAG laser with diffuser optics. The experimental results showed an
acceptable agreement with the prediction made by our method in all studied cases. We demonstrate that the shape
and droplet size distribution are affected by the impact angle, while the velocity of the ejected droplets remains
constant in the azimuthal direction
Droplet splashing on thin moving films at high Weber numbers
The influence of a thin moving film on the splashing of droplets was investigated experimentally at high Weber numbers. This study was conducted using a flywheel experiment fitted with a new film gener- ation system, which allows for the production of thin films with variable mean velocity for different liquids. The thickness was measured using a miniature confocal-chromatic sensor during the rotation of the flywheel. Using shadowgraph techniques, the splashing process was analyzed and the evolution of the crown height and diameter were described. It was also demonstrated that the film velocity and thickness influence the development of the crown geometry. The combination of a high-speed and a high-resolution camera allowed us to observe two different instabilities that accelerate the breakup pro- cess, leading to a complete atomization of the crown into secondary droplets. The instabilities observed were: spreading holes and a separation from the crown base. Using the formed holes, we calculated the lamella thickness using two different methods, yielding a constant value of 31 ±3 μm for all the exper- iments. We estimated both the time at which the hole instabilities appeared and the time at which the breakup process began. Moreover, it was demonstrated that small bubbles in the lamella are responsible for the hole formation. We also showed that the entire breakup process is delayed by increasing the film flow velocity, regardless of the Weber number
High Speed Visualization of Droplets Impacting with a Dry Surface at High Weber Numbers
The focus of this article is to describe the evolution of the spreading diameter
and secondary droplets generated by splashing. High-speed visualization was
used to study the time evolution of water droplets impacts with dry surfaces at Weber numbers between 3,500 and 10,000. Different prediction models of the maximal spreading diameter have been compared with each other and with the experimental data. A similarity between the spreading rates was observed in the last stage of the impact at highWeber numbers. The time evolution of the secondary droplets and the formation of the crown was observed and analyzed at the different Weber numbers
Mitochondrial genomes of the key zooplankton copepods Arctic Calanus glacialis and North Atlantic Calanus finmarchicus with the longest crustacean non-coding regions
We determined the nearly complete mitochondrial genomes of the Arctic Calanus glacialis and its North Atlantic sibling Calanus finmarchicus, which are key zooplankton components in marine ecosystems. The sequenced part of C. glacialis mitogenome is 27,342 bp long and consists of two contigs, while for C. finmarchicus it is 29,462 bp and six contigs, what makes them the longest reported copepod mitogenomes. The typical set of metazoan mitochondrial genes is present in these mitogenomes, although the non-coding regions (NCRs) are unusually long and complex. The mitogenomes of the closest species C. glacialis and C. finmarchicus, followed by the North Pacific C. sinicus, are structurally similar and differ from the much more typical of deep-water, Arctic C. hyperboreus. This evolutionary trend for the expansion of NCRs within the Calanus mitogenomes increases mitochondrial DNA density, what resulted in its similar density to the nuclear genome. Given large differences in the length and structure of C. glacialis and C. finmarchicus mitogenomes, we conclude that the species are genetically distinct and thus cannot hybridize. The molecular resources presented here: the mitogenomic and rDNA sequences, and the database of repetitive elements should facilitate the development of genetic markers suitable in pursuing evolutionary research in copepods.Polish Ministry of Science and Higher Education [Iuventus Plus] [IP2014 050573]; FCT-CCMAR Portugal [Multi/04326/2013
Role of surrounding gas in the outcome of droplet splashing
This study investigates the influence of the surrounding gas on a droplet impacting a
smooth dry glass surface at high Weber and Reynolds numbers. It was performed using a
flywheel experiment and different gases at ambient pressure. We analyzed the splashing
outcome by measuring the size, velocity, and angle of the secondary droplets and by
calculating the total volume ejected. We show that gas entrapment is not the mechanism
responsible for splashing at high Weber and Reynolds numbers. We demonstrate that
splashing is influenced by the density, followed by the viscosity, and last by the mean
free path of the surrounding gas. Furthermore, the surrounding gas primarily affects the
number of secondary droplets ejected and their ejection angle, whereas the droplet size
and horizontal velocity are independent of the surrounding gas properties. We provide the
first theoretical expression for the total volume ejected using the theory of Riboux and
Gordillo [Phys. Rev. Lett. 113, 024507 (2014)], which attributes the secondary droplet
generation to a lift force experienced by spreading lamella. The relationship between the
ejected volume and the splashing parameter is described by a power function
Fabrication of submicron structures in nanoparticle/polymer composite by holographic lithography and reactive ion etching
We report on the fabrication of nanoparticle/polymer submicron structures by combining holographic lithography and reactive ion etching. Silica nanoparticles are uniformly dispersed in a (SU8) polymer matrix at a high concentration, and in situ polymerization (cross-linking) is used to form a nanoparticle/polymer composite. Another photosensitive SU8 layer cast upon the nanoparticle/SU8 composite layer is structured through holographic lithography, whose pattern is finally transferred to the nanoparticle/SU8 layer by the reactive ion etching process. Honeycomb structures in a submicron scale are experimentally realized in the nanoparticle/SU8 composite.This work was supported in part by the US Air Force
Office for Scientific Research and in part by National Basic
Research Program 973 of China No. 2004CB719800
A measurement of the evolution of Interatomic Coulombic Decay in the time domain
During the last 15 years a novel decay mechanism of excited atoms has been
discovered and investigated. This so called ''Interatomic Coulombic Decay''
(ICD) involves the chemical environment of the electronically excited atom: the
excitation energy is transferred (in many cases over long distances) to a
neighbor of the initially excited particle usually ionizing that neighbor. It
turned out that ICD is a very common decay route in nature as it occurs across
van-der-Waals and hydrogen bonds. The time evolution of ICD is predicted to be
highly complex, as its efficiency strongly depends on the distance of the atoms
involved and this distance typically changes during the decay. Here we present
the first direct measurement of the temporal evolution of ICD using a novel
experimental approach.Comment: 6 pages, 4 figures, submitted to PR
Vibrationally Resolved Decay Width of Interatomic Coulombic Decay in HeNe
We investigate the ionization of HeNe from below the He 1s3p excitation to
the He ionization threshold. We observe HeNe ions with an enhancement by
more than a factor of 60 when the He side couples resonantly to the radiation
field. These ions are an experimental proof of a two-center resonant
photoionization mechanism predicted by Najjari et al. [Phys. Rev. Lett. 105,
153002 (2010)]. Furthermore, our data provide electronic and vibrational state
resolved decay widths of interatomic Coulombic decay (ICD) in HeNe dimers. We
find that the ICD lifetime strongly increases with increasing vibrational
state.Comment: 7 pages, 5 figure
Interatomic-Coulombic-decay-induced recapture of photoelectrons in helium dimers
We investigate the onset of photoionization shakeup induced interatomic
Coulombic decay (ICD) in He2 at the He+*(n = 2) threshold by detecting two He+
ions in coincidence. We find this threshold to be shifted towards higher
energies compared to the same threshold in the monomer. The shifted onset of
ion pairs created by ICD is attributed to a recapture of the threshold
photoelectron after the emission of the faster ICD electron.Comment: 5 Pages, 2 Figure
100: Fluid Related Complications with Filgrastim (G-CSF) 10 mcg/kg Once Daily Versus 5 mcg/kg Twice Daily in Amyloidosis Patients Undergoing Peripheral Blood Stem Cell Mobilization
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