Search results for "Ezers"
showing 10 items of 87 documents
Forces between colloidal particles in aqueous solutions containing monovalent and multivalent ions
2017
The present article provides an overview of the recent progress in the direct force measurements between individual pairs of colloidal particles in aqueous salt solutions. Results obtained by two different techniques are being highlighted, namely with the atomic force microscope (AFM) and optical tweezers. One finds that the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO) represents an accurate description of the force profiles even in the presence of multivalent ions, typically down to distances of few nanometers. However, the corresponding Hamaker constants and diffuse layer potentials must be extracted from the force profiles. At low salt concentrations, double layer f…
On-chip periodic arrays of optical traps based on the superposition of guided modes in silicon waveguides
2019
Since the pioneering work of Kawata and Tani [1], photonic waveguides have long been regarded as efficient optical conveyor belts for potential lab-on-a-chip applications. Indeed, near-field optical forces arising at the surface of such waveguides lead to efficient on-chip guided propulsion of micro- and even nanoparticles [2], as well as cells and bacteria in liquid solutions [3]. However, achieving stable and precisely controlled optical trapping of particles at the surface of a waveguide has been made possible only recently, and even then, it still requires complex photonic electro-optic tools to produce and handle on-chip standing waves [4].
Quantitative Optical Trapping of Single Gold Nanorods
2008
We report a quantitative analysis of the forces acting on optically trapped single gold nanorods. Individual nanorods with diameters between 8 and 44 nm and aspect ratios between 1.7 and 5.6 were stably trapped in three dimensions using a laser wavelength exceeding their plasmon resonance wavelengths. The interaction between the electromagnetic field of an optical trap and a single gold nanorod correlated with particle polarizability, which is a function of both particle volume and aspect ratio.
Optofluidic taming of a colloidal dimer with a silicon nanocavity
2014
International audience; We report here the optical trapping of a heterogeneous colloidal dimer above a photonic crystal nanocavity used as an on-chip optical tweezer. The trapped dimer consists of a cluster of two dielectric microbeads of different sizes linked by van der Waals forces. The smallest bead, 1 μm in diameter, is observed to be preferentially trapped by the nanotweezer, leaving the second bead untrapped. The rotational nature of the trapped dimer Brownian motion is first evidenced. Then, in the presence of a fluid flow, control of its orientation and rotation is achieved. The whole system is found to show high rotational degrees of freedom, thereby acting as an effective flow-se…
Astronomiskās un dabas parādības aizvēsturē Ziemeļeiropā: atspoguļojums vēstures avotos un arheoloģiskajā materiālā
2021
Cilvēka dzīve aizvēsturē bija ļoti cieši saista ar dabu. Līdz ar pāreju uz ražotājsaimniecību vēlā akmens laikmeta beigās, bet īpaši sākot ar bronzas laikmetu, izveidojās ideoloģija, kurā centrālo vietu ieņēma Saule un ar to saistīto gadskārtu cikli. Solārā un lunārā simbolika plaši pārstāvēta Ziemeļeiropas, arī Latvijas arheoloģiskajā materiālā. Dabas un astronomiskās parādības minētas arī pirmajos rakstītajos avotos, bet to sekas – īpaši dabas katastrofu sekas, fiksējamas arī arheoloģiskajā materiālā.
Alūksnes ezera zivju sabiedrība – tās sastāvs un zivju sugu barošanās 2014. gada vasaras sezonā
2015
Bakalaura darbs izstrādāts Vides Risinājumu institūta un Alūksnes novada pašvaldības projekta „Alūksnes ezera gultnes, piekrastes zonas veģetācijas un ekosistēmas pētniecība” ietvaros. Darbā mērķis bija raksturot Alūksnes ezera zivju sabiedrības sastāvu un izpētīt dominējošo zivju sugu barošanās paradumus. Zinātniskā kontrolzveja pamatā veikta pēc Eiropas un Latvijas zivju paraugu ievākšanas standarta, izmantojot Nordic tipa daudzacu žauntīklus. Konstatēts, ka Alūksnes ezera zivju sabiedrība atbilst mērenās klimata joslas mezotrofu ezeru ihtiofaunai un ka no konkrētām zivju sugām gan pēc biomasas, gan pēc skaita dominēja asari Perca fluviatilis. Saistībā ar zivju barošanās paradumiem secinā…
Discrete-Gauss states and the generation of focussing dark beams
2014
Discrete-Gauss states are a new class of gaussian solutions of the free Schr\"odinger equation owning discrete rotational symmetry. They are obtained by acting with a discrete deformation operator onto Laguerre-Gauss modes. We present a general analytical construction of these states and show the necessary and sufficient condition for them to host embedded dark beams structures. We unveil the intimate connection between discrete rotational symmetry, orbital angular momentum, and the generation of focussing dark beams. The distinguishing features of focussing dark beams are discussed. The potential applications of Discrete-Gauss states in advanced optical trapping and quantum information pro…
Single-File Diffusion of Colloids in One-Dimensional Channels
2004
We study the diffusive behavior of colloidal particles which are confined to one-dimensional channels generated by scanning optical tweezers. At long times t, the mean-square displacement is found to scale as t(1/2), which is expected for systems where single-file diffusion occurs. In addition, we experimentally obtain the long-time, self-diffusive behavior from the short-time collective density fluctuations of the system as suggested by a recent analytical approach [Phys. Rev. Lett. 90, 180602 (2003)]. published
Engineering NonBinary Rydberg Interactions via Phonons in an Optical Lattice
2019
Coupling electronic and vibrational degrees of freedom of Rydberg atoms held in optical tweezer arrays offers a flexible mechanism for creating and controlling atom-atom interactions. We find that the state-dependent coupling between Rydberg atoms and local oscillator modes gives rise to two- and three-body interactions which are controllable through the strength of the local confinement. This approach even permits the cancellation of two-body terms such that three-body interactions become dominant. We analyze the structure of these interactions on two-dimensional bipartite lattice geometries and explore the impact of three-body interactions on system ground state on a square lattice. Focus…
Time-multiplexed chromatic-controlled axial diffractive optical elements
2010
Programmable diffractive optical elements DOEs with axial response have many interesting applications, including diffractive lenses, axicons, and optical tweezers. In all these cases, it is essential to properly select the modulation configuration of the spatial light modulator SLM where the DOE is displayed, in order to avoid the undiffracted zero order component that appears on axis and overlaps the desired axial response. However, in general, the chromatic dispersion in liquid crystal SLMs prevents the cancellation of the zero order for a broadband light source, thus limiting the possibilities for polychromatic program- mable axial DOEs. We operate a ferroelectric liquid crystal on silic…