95 research outputs found
Dirac particle in the presence of plane wave and constant magnetic fields: Path integral approach
The Green function (GF) related to the problem of a Dirac particle
interacting with a plane wave and constant magnetic fields is calculated in the
framework of path integral via Alexandrou et al. formalism according to the
so-called global projection. As a tool of calculation, we introduce two
identities (constraints) into this formalism, their main role is the reduction
of integrals dimension and the emergence in a natural way of some classical
paths, and due to the existence of constant electromagnetic field, we have used
the technique of fluctuations. Hence the calculation of the (GF) is reduced to
a known gaussian integral plus a contribution of the effective classical
action.Comment: 12 pages, no figure
Tilted Micro Air Jet for Flow Control
In this paper, we present an interesting method to microfabricate a tilted
micro air jet generator. We used the well-know deep reactive ion etching (DRIE)
technique in order to realize in a silicon substrate a double side etching. For
aircraft and cars, micro air jets will take an important place for fluid
control. Micro air jets are characterized by their speed, frequency and tilt.
Usually, this micro air jets are produced by fluidic microsystems. We presented
experimental results about micro tilted air jets. A comparison between finite
element method simulation, theory and experimental results are performed to
define the microsystem geometry leading a specific air jet angle
An Efficient and Decentralized Blockchain-based Commercial Alternative (Full Version)
While online interactions and exchanges have grown exponentially over the
past decade, most commercial infrastructures still operate through centralized
protocols, and their success essentially depends on trust between different
economic actors. Digital advances such as blockchain technology has led to a
massive wave of \textit{Decentralized Ledger Technology} (\textit{DLT})
initiatives, protocols and solutions. This advance makes it possible to
implement trustless systems in the real world, which, combined with appropriate
economic and participatory incentives, would foster the proper functioning and
drive the adoption of a decentralized platform among different actors. This
paper describes an alternative to current commercial structures and networks by
introducing \textit{Lyzis Labs}, which is is an incentive-driven and democratic
protocol designed to support a decentralized online marketplace, based on
blockchain technology. The proposal, \textit{Lyzis Marketplace}, allows to
connect two or more people in a decentralized and secure way without having to
rely on a \textit{Trusted Third Party} (\textit{TTP}) in order to perform
physical asset exchanges while mainly providing transparent and fully protected
data storage. This approach can potentially lead to the creation of a
permissionless, efficient, secure and transparent business environment where
each user can gain purchasing and decision-making power by supporting the
collective welfare while following their personal interests during their
various interactions on the network.Comment: 62 pages, 9 figures, 19 table
Microsensors and image processing for single oocyte qualification: toward multiparametric determination of the best time for fertilization
International audienceDuring intracytoplasmic sperm injection (ICSI) attempts, oocytes reaching metaphase II are microinjected. A morphological examination under a microscope is the usual method for determining oocyte maturity. The level of oocyte maturity is based on the meiotic status (Germinal Vesicle, metaphase I and metaphase II) of the oocytes with respect to their increasing maturity. In this letter, we summarize the studies conducted to analyze cytoplasm maturity using various microsystems and image processing. Optical microsystems are used to measure the transmission spectra and refractive index of the oocytes. We compared the transmission spectra measurements to the transmission electron microscopy results. Karhunen-Loeve transform is also used to evaluate the maturity of the oocytes. To summarize, optical analysis techniques are a minimally invasive technology allowing cytoplasm maturity to be assessed. Oocytes should not only be qualified in terms of GV, MI or MII, but also regarding their temporal evolution over the course of these maturation stages. The ultimate aim of this work is to describe the maturation of the oocytes by a trajectory in a multidimensional space and to determine when would be the best time for successful fertilization
Micropositioning and Fast Transport Using a Contactless Micro-Conveyor
International audienceThe micro-conveyor is a 9 x 9 mm2 manipulation surface able to move millimeter-sized planar objects in the four cardinal directions using air flows. Thanks to a specific design, the air flow comes through a network of micro-channels connected to an array of micro-nozzles. Thus, the micro-conveyor generates an array of tilted air jets that lifts and moves the object in the required direction. In this paper, we characterize the device for transport and positioning tasks and evaluate its performances in terms of speed, resolution and repeatability. We show that the micro-conveyor is able to move the object with a speed up to 137 mm* s-1 in less than 100 ms whereas the positioning repeatability is around 17.7 ”m with feedback control. The smallest step the object can do is 0.3 ”m (positioning resolution). Moreover, we estimated thanks to a dynamic model that the speed could reach 456 mm* s-1 if several micro-conveyors were used to form a conveying line
Safeguarding Physical Sneaker Sale Through a Decentralized Medium
Sneakers were designated as the most counterfeited fashion item online, with three times more risk in a trade than any other fashion purchase. As the market expands, the current sneaker scene displays several vulnerabilities and trust flaws, mostly related to the legitimacy of assets or actors. In this paper, we investigate various blockchain-based mechanisms to address these large-scale trust issues. We argue that (i) pre-certified and tracked assets through the use of non-fungible tokens can ensure the genuine nature of an asset and authenticate its owner more effectively during peer-to-peer trading across a marketplace; (ii) a game-theoretic-based system with economic incentives for participating users can greatly reduce the rate of online fraud and address missed delivery deadlines; (iii) a decentralized dispute resolution system biased in favour of an honest party can solve potential conflicts more reliably
Labâonâaâchip biophotonics: its application to assisted reproductive technologies
With the benefits of automation, sensitivity and precision, microfluidics has enabled complex and otherwise tedious experiments. Lately, labâonâaâchip (LOC) has proven to be a useful tool for enhancing nonâinvasive assisted reproductive technology (ART). Nonâinvasive gamete and embryo assessment has largely been through periodic morpohological assessment using optical microscopy and early LOC ART was the same. As we realize that morphological assessment is a poor indication of gamete or embryo health, more advanced biophotonics has emerged in LOC ART to assay for metabolites or gamete separation via optoelectrical tweezers. Offâchip, even more advanced biophotonics with broad spectrum analysis of metabolites and secretomes has been developed that show even higher accuracy to predicting reproductive potential. The integration of broad spectrum metabolite analysis into LOC ART is an exciting future that merges automation and sensitivity with the already highly accurate and strong predictive power of biophotonics. (© 2012 WILEYâVCH Verlag GmbH & Co. KGaA, Weinheim)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92358/1/650_ftp.pd
MicrosystĂšmes et microcapteurs pour les sciences du vivant
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