56 research outputs found
Behavior of Droplets in Microfluidic System with T-Junction
Micro droplet formation is considered as a growing
emerging area of research due to its wide-range application in
chemistry as well as biology. The mechanism of micro droplet
formation using two immiscible liquids running through a T-junction
has been widely studied.
We believe that the flow of these two immiscible phases can be of
greater important factor that could have an impact on out-flow
hydrodynamic behavior, the droplets generated and the size of the
droplets. In this study, the type of the capillary tubes used also
represents another important factor that can have an impact on the
generation of micro droplets.
The tygon capillary tubing with hydrophilic inner surface doesn't
allow regular out-flows due to the fact that the continuous phase
doesn't adhere to the wall of the capillary inner surface.
Teflon capillary tubing, presents better wettability than tygon
tubing, and allows to obtain steady and regular regimes of out-flow,
and the micro droplets are homogeneoussize.
The size of the droplets is directly dependent on the flows of the
continuous and dispersed phases. Thus, as increasing the flow of the
continuous phase, to flow of the dispersed phase stationary, the size
of the drops decreases. Inversely, while increasing the flow of the
dispersed phase, to flow of the continuous phase stationary, the size
of the droplet increases
Bloch oscillations of ultracold atoms: a tool for a metrological determination of
We use Bloch oscillations in a horizontal moving standing wave to transfer a
large number of photon recoils to atoms with a high efficiency (99.5% per
cycle). By measuring the photon recoil of , using velocity selective
Raman transitions to select a subrecoil velocity class and to measure the final
accelerated velocity class, we have determined with a relative
precision of 0.4 ppm. To exploit the high momentum transfer efficiency of our
method, we are developing a vertical standing wave set-up. This will allow us
to measure better than and hence the fine structure
constant with an uncertainty close to the most accurate value coming
from the () determination
Self-stabilizing algorithms for Connected Vertex Cover and Clique decomposition problems
In many wireless networks, there is no fixed physical backbone nor
centralized network management. The nodes of such a network have to
self-organize in order to maintain a virtual backbone used to route messages.
Moreover, any node of the network can be a priori at the origin of a malicious
attack. Thus, in one hand the backbone must be fault-tolerant and in other hand
it can be useful to monitor all network communications to identify an attack as
soon as possible. We are interested in the minimum \emph{Connected Vertex
Cover} problem, a generalization of the classical minimum Vertex Cover problem,
which allows to obtain a connected backbone. Recently, Delbot et
al.~\cite{DelbotLP13} proposed a new centralized algorithm with a constant
approximation ratio of for this problem. In this paper, we propose a
distributed and self-stabilizing version of their algorithm with the same
approximation guarantee. To the best knowledge of the authors, it is the first
distributed and fault-tolerant algorithm for this problem. The approach
followed to solve the considered problem is based on the construction of a
connected minimal clique partition. Therefore, we also design the first
distributed self-stabilizing algorithm for this problem, which is of
independent interest
Progress towards an accurate determination of the Boltzmann constant by Doppler spectroscopy
In this paper, we present significant progress performed on an experiment
dedicated to the determination of the Boltzmann constant, k, by accurately
measuring the Doppler absorption profile of a line in a gas of ammonia at
thermal equilibrium. This optical method based on the first principles of
statistical mechanics is an alternative to the acoustical method which has led
to the unique determination of k published by the CODATA with a relative
accuracy of 1.7 ppm. We report on the first measurement of the Boltzmann
constant by laser spectroscopy with a statistical uncertainty below 10 ppm,
more specifically 6.4 ppm. This progress results from improvements in the
detection method and in the statistical treatment of the data. In addition, we
have recorded the hyperfine structure of the probed saQ(6,3) rovibrational line
of ammonia by saturation spectroscopy and thus determine very precisely the
induced 4.36 (2) ppm broadening of the absorption linewidth. We also show that,
in our well chosen experimental conditions, saturation effects have a
negligible impact on the linewidth. Finally, we draw the route to future
developments for an absolute determination of with an accuracy of a few ppm.Comment: 22 pages, 11 figure
NiâZn hydroxide-based bi-phase multiscale porous nanohybrids : physico-chemical properties
Please read abstract in the article.The Algerian minister programhttps://link.springer.com/journal/132042020-05-25hj2020Physic
Proposal for new experimental schemes to realize the Avogadro constant
We propose two experimental schemes to determine and so to realize the
Avogadro constant at the level of 10 or better with a watt
balance experiment and a cold atom experiment measuring (where is
the Planck constant and the mass of the atom ). We give some
prospects about achievable uncertainties and we discuss the opportunity to test
the existence of possible unknown correction factors for the Josephson effect
and quantum Hall effect
Development of a PbWO4 Detector for Single-Shot Positron Annihilation Lifetime Spectroscopy at the GBAR Experiment
We have developed a PbWO4 (PWO) detector with a large dynamic range to measure the intensity of a positron beam and the absolute density of the ortho-positronium (o-Ps) cloud it creates. A simulation study shows that a setup based on such detectors may be used to determine the angular distribution of the emission and reflection of o-Ps to reduce part of the uncertainties of the measurement. These will allow to improve the precision in the measurement of the cross-section for the (anti)hydrogen formation by (anti)proton-positronium charge exchange and to optimize the yield of antihydrogen ion which is an essential parameter in the GBAR experiment
Towards a test of the weak equivalence principle of gravity using anti-hydrogen at CERN
International audienceThe aim of the GBAR (Gravitational Behavior of Antimatter at Rest) experiment is to measure the free fall acceleration of an antihydrogen atom, in the terrestrial gravitational field at CERN and therefore test the Weak Equivalence Principle with antimatter. The aim is to measure the local gravity with a 1% uncertainty which can be reduced to few parts of 10-3
ELGAR - A European Laboratory for Gravitation and Atom-interferometric Research
Gravitational waves (GWs) were observed for the first time in 2015, one century after Einstein predicted their existence. There is now growing interest to extend the detection bandwidth to low frequency. The scientific potential of multi-frequency GW astronomy is enormous as it would enable to obtain a more complete picture of cosmic events and mechanisms. This is a unique and entirely new opportunity for the future of astronomy, the success of which depends upon the decisions being made on existing and new infrastructures. The prospect of combining observations from the future space-based instrument LISA together with third generation ground based detectors will open the way toward multi-band GW astronomy, but will leave the infrasound (0.1â10 Hz) band uncovered. GW detectors based on matter wave interferometry promise to fill such a sensitivity gap. We propose the European Laboratory for Gravitation and Atom-interferometric Research (ELGAR), an underground infrastructure based on the latest progress in atomic physics, to study spaceâtime and gravitation with the primary goal of detecting GWs in the infrasound band. ELGAR will directly inherit from large research facilities now being built in Europe for the study of large scale atom interferometry and will drive new pan-European synergies from top research centers developing quantum sensors. ELGAR will measure GW radiation in the infrasound band with a peak strain sensitivity of 3.3 x 10 [hoch]-20 / [Wurzel] Hz at 1.7 Hz. The antenna will have an impact on diverse fundamental and applied research fields beyond GW astronomy, including gravitation, general relativity, and geology
Fault Tolerant Network Constructors
In this work, we consider adversarial crash faults of nodes in the network
constructors model Michail and Spirakis, 2016. We first show that,
without further assumptions, the class of graph languages that can be (stably)
constructed under crash faults is non-empty but small. In particular, if an
unbounded number of crash faults may occur, we prove that (i) the only
constructible graph language is that of spanning cliques and (ii) a strong
impossibility result holds even if the size of the graphs that the protocol
outputs in populations of size need only grow with (the remaining nodes
being waste). When there is a finite upper bound on the number of faults,
we show that it is impossible to construct any non-hereditary graph language.
On the positive side, by relaxing our requirements we prove that: (i)
permitting linear waste enables to construct on nodes, any graph
language that is constructible in the fault-free case, (ii) partial
constructibility (i.e. not having to generate all graphs in the language)
allows the construction of a large class of graph languages. We then extend the
original model with a minimal form of fault notifications. Our main result here
is a fault-tolerant universal constructor: We develop a fault-tolerant protocol
for spanning line and use it to simulate a linear-space Turing Machine .
This allows a fault-tolerant construction of any graph accepted by in
linear space, with waste , where is the number of
faults in the execution. We then prove that increasing the permissible waste to
allows the construction of graphs accepted by an
-space Turing Machine, which is asymptotically the maximum simulation
space that we can hope for in this model. Finally, we show that logarithmic
local memories can be exploited for a no-waste fault-tolerant simulation of any
such protocol
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