Search results for "ezers"

Assembly of microparticles by optical trapping with a photonic crystal nanocavity

2012

International audience; In this work, we report the auto-assembly experiments of micrometer sized particles by optical trapping in the evanescent field of a photonic crystal nanocavity. The nanocavity is inserted inside an optofluidic cell designed to enable the real time control of the nanoresonator transmittance as well as the real time visualization of the particles motion in the vicinity of the nanocavity. It is demonstrated that the optical trap above the cavity enables the assembly of multiple particles in respect of different stable conformations.

Latvijas ūdeņu vides pētījumi un aizsardzība: rakstu krājums (Rīga, 2017. gada 2. februāris)

2017

Paleoģeogrāfisko apstākļu izmaiņas un cilvēku klātbūtnes liecības Vilkmuižas un Talsu ezeru nogulumos

2017

Maģistra darbā sasniegts mērķis izzināt paleoģeogrāfiskos apstākļus Vilkmuižas un Talsu ezera attīstības laikā un, veicot ezera nogulumu pētījumus, noskaidrot liecības par seno cilvēku klātbūtni. Darbā sniegts neliels Vilkmuižas un Talsu ezeru raksturojums, kā arī pētījumā izmantoto metožu apraksts. Savukārt iegūtie rezultāti ļauj veikt paleoģeogrāfisko apstākļu izmaiņu interpretāciju abu ezeru attīstības gaitu. Pētījumā tiek meklētas cilvēku liecības ezeru nogulumos, īpaši interesējoties par iespējamo seno kuršu 12.-14.gs darbību liecībām, tomēr konkrētu pierādījumu seno kuršu darbībai netika iegūti, attiecīgā datējuma trūkuma dēļ. Iegūtie rezultāti ataino Vilkmuižas ezera ūdens līmeņa atš…

Synthesis and Photodynamics of Fluorescent Blue BODIPY-Porphyrin Tweezers Linked by Triazole Rings

2012

Novel zinc porphyrin tweezers in which two zinc porphyrins were connected with π-conjugated boron dipyrromethenes (BDP meso-Por(2) and BDP β-Por(2)) through triazole rings were synthesized to investigate the photoinduced energy transfer and electron transfer. The UV-vis spectrum of BDP β-Por(2) which has less bulky substituents than BDP meso-Por(2) exhibits splitting of the Soret band as a result of the interaction between porphyrins of BDP β-Por(2) in the excited state. Such interaction between porphyrins of both BDP β-Por(2) and BDP meso-Por(2) is dominant at room temperature, while the coordination of the nitrogen atoms of the triazole rings to the zinc ions of the porphyrins occurs at l…

Synthesis and Characterization of Carbazole-Linked Porphyrin Tweezers

2015

Herein the synthesis, spectroscopic characterization, two-photon absorption and electrochemical properties of 3,6-disubstituted carbazole tweezers is reported. A dimer resulting from a Glaser homocoupling was isolated during a Sonogashira coupling reaction between a diethynyl-carbazole spacer and a 5-bromo-triarylporphyrin and the properties of this original compound were compared with the 3,6-disubstituted carbazole bisporphyrin tweezers. The dyads reported herein present a two-photon absorption maximum at 920 nm with two-photon absorption cross-section in the 1200 GM range. Despite a strong linear absorption in the Soret region and moderate fluorescence quantum yield, they both lead to a …

Putnu koloniju ietekme uz iegrimušo augu veģetāciju Engures ezerā

2020

Maģistra darbs “Putnu koloniju ietekme uz iegrimušo augu veģetāciju Engures ezerā” tika sākts izstrādāt 2018. gada augustā. Materiāli ievākti 2018. gada augustā un septembrī. Darba izstrāde veikta Latvijas Universitātes Bioloģijas fakultātes Botānikas un ekoloģijas katedrā. Darba mērķis ir noteikt putnu koloniju ietekmi uz iegrimušo veģetāciju Engures ezerā. Engures ezers ir mieturaļģu ezers, kura ekosistēmā pēdējos gados notiek izmaiņas, ko veicinājušas nesen izveidotās kormorānu Phalacrocarax carbo kolonijas. To ietekme uz ezeru līdz šim nav pētīta. Kļuvis vairāk arī gulbju Cygnus olor un lauču Fulica atra, kas barojas ar mieturaļģēm. Tiek paredzēts, ka eitrofikācijas rezultātā mieturaļģe…

Inside Cover: Synthesis and Characterization of Carbazole-Linked Porphyrin Tweezers (Chem. Eur. J. 34/2015)

2015

Diffusion of colloids in one-dimensional light channels

2004

Single-file diffusion (SFD), prevalent in many chemical and biological processes, refers to the one-dimensional motion of interacting particles in pores which are so narrow that the mutual passage of particles is excluded. Since the sequence of particles in such a situation remains unaffected over time t, this leads to strong deviations from normal diffusion, e.g. an increase of the particle mean-square-displacement as the square root of t. We present experimental results of the diffusive behaviour of colloidal particles in one-dimensional channels with varying particle density. The channels are realized by means of a scanning optical tweezers. Based on a new analytical approach (Kollmann 2…

Nanofiber-based optical trapping of cold neutral atoms

2012

We present experimental techniques and results related to the optimization and characterization of our nanofiber-based atom trap [Vetsch et al., Phys. Rev. Lett. 104, 203603 (2010)]. The atoms are confined in an optical lattice which is created using a two-color evanescent field surrounding the optical nanofiber. For this purpose, the polarization state of the trapping light fields has to be properly adjusted. We demonstrate that this can be accomplished by analyzing the light scattered by the nanofiber. Furthermore, we show that loading the nanofiber trap from a magneto-optical trap leads to sub-Doppler temperatures of the trapped atomic ensemble and yields a sub-Poissonian distribution of…

Fractal zone plates with variable lacunarity.

2009

Fractal zone plates (FZPs), i.e., zone plates with fractal structure, have been recently introduced in optics. These zone plates are distinguished by the fractal focusing structure they provide along the optical axis. In this paper we study the effects on this axial response of an important descriptor of fractals: the lacunarity. It is shown that this parameter drastically affects the profile of the irradiance response along the optical axis. In spite of this fact, the axial behavior always has the self-similarity characteristics of the FZP itself.