Effect of Large Quantum Correlations in “Russian Doll” Quantum Dots: Impact on MEG Solar Cells

SCMP : the 21st symposium on condensed matter physics : book of abstracts; 26-30 June 2023, Belgrad

Absorption characteristics of a quantum dot array induced intermediate band: implications for solar cell design

We present a theoretical study of the electronic and absorption properties of the intermediate band (IB) formed by a three dimensional structure of InAs/GaAs quantum dots (QDs) arranged in a periodic array. Analysis of the electronic and absorption structures suggests that the most promising design for an IB solar cell material, which will exhibit its own quasi-Fermi level, is to employ small QDs (~6–12 nm QD lateral size). The use of larger QDs leads to extension of the absorption spectra into a longer wavelength region but does not provide a separate IB in the forbidden energy gap

Morfološke osobitosti pasivnog fleksornog mehanizma ptica s različitim rasporedom prstiju

Birds possess a mechanism which allows passive flexion of the digits of the hind limbs which consists of two components: “automatic digital flexor mechanism” (ADFM) and “digital tendon-locking mechanism” (DTLM). The aim of this paper was to establish the existence and specificities of those components in examples of birds with anisodactyl (domestic chickens) and zygodactyl (parrots) digit layout using standard anatomical dissection and histological methods. Spatial distribution of the parrots’ muscles with a central role in DTLM (M. flexor digitorum longus and m. flexor hallucis longus) was the same as the chickens’. The plantar position of the fourth digit, which makes the difference between the anisodactyl and the zygodactyl digit layouts, did not cause changes in the position and function of this flexor muscles. The domestic chickens’ tendon sheath ridges, as well as the tendon tubercles of the flexor muscles were less developed while the parrots’ tubercles and ridges were clearly defined and the differences in their morphology were visible. There were no chondrogenic elements or they were barely noticeable in the parrots’ tendons. A potential cause of these distinctions could be the difference in the load which the tendons endure due to the different biomechanical composition. The parrots primarily inhabit trees where they move agilely around by grasping the branches. The Galliformes have a much larger body mass which is a consequence of their life on the ground, so the flexor muscle tendons suffer a greater load than the parrots and the cartilage tissue embedded in the tendon itself could act to distribute the weight of the body borne by the foot and the tendonPtice posjeduju mehanizam koji im omogućuje pasivnu fleksiju prstiju noge, a sastoji se od dvije komponente: automatskog digitalnog fleksornog mehanizma (ADFM) i digitalnog mehanizma zatvaranja tetiva (DTLM). Cilj ovoga rada bio je ustanoviti postojanje i specifičnost ovih komponenti u predstavnika ptica s anizodaktilnim (domaća kokoš) i zigodaktilnim (papige) rasporedom prstiju, primjenjujući standardnu anatomsku sekciju i histološke metode. Prostorna organizacija mišića koji imaju središnju ulogu u DTLM-u (m. flexor digitorum longus i m. flexor hallucis longus) jednaka je u papiga i domaće kokoši. Plantarni položaj četvrtog prsta, što čini razliku između anizodaktilnog i zigodaktilnog rasporeda prstiju, nije uvjetovao promjene položaja i funkcije tih fleksornih mišića. Nabori tetivnih ovojnica i kvržice na tetivama fleksornih mišića bili su slabije razvijeni u domaće kokoši, dok su u papiga nabori i kvržice bili jasno definirani, a njihove morfološke razlike vidljive. Hondrogeni elementi nedostaju ili su jedva zamjetni u tetivama papiga. Mogući uzrok ovoj pojavi mogla bi biti razlika u opterećenju koje trpe tetive zbog različitih biomehaničkih prilika. Papige su primarno vezane za krošnje drveća gdje se vrlo spretno kreću prihvatom za grane. Kod galiformnih je ptica masa tijela znatno veća, što je posljedica prilagodbe životu na tlu, pa tetive fleksornih mišića trpe veće opterećenje nego kod papiga, dok hrskavično tkivo uklopljeno u samu tetivu može djelovati na raspodjelu mase tijela koje podnosi stopalo, pa samim tim i tetiva

Analysis of energy gap opening in graphene oxide

The utilisation of graphene structures as photonics materials mandates that an optically active electronic energy gap be formed. Opening of a gap in graphene has been demonstrated by functionalisation with H, F, or O atoms, while experimental observations of graphene oxide have hinted at interesting optical properties, with the potential for absorption of visible light. As such, our analysis is focused on O functionalisation of graphene. We present results from extensive ab initio and hybrid DFT calculations, demonstrating the creation of an optically active gap

Development of ground motion record surface and response spectra surface

The paper is presenting a mathematical formulation of an originally developed ground motion record surface (GMRS) and response spectra surface (RSS) for the presentation of 2D seismic ground motion records (GMR) and the corresponding response spectra (RS), respectively. These surfaces are constructed by transformation from 2D polar coordinate system to a 3D cylindrical coordinate system and then to the 3D orthogonal coordinate system. The principle of application of three orthogonal coordinates for each discrete value is used in order to achieve easy manipulation and interpolation of spatial surface. Scaling of accelerograms was carried out using two procedures: the Least Square Method (LSM) and Spectral Matching (SM)

Rasejanje svetlosti i tehnike u biološkim i biomedicinskim problemima

Biološke i biomedicinske sredine sadrže veliki broj čestica različitog oblika i veličine koje predstavljaju potencijalne centre rasejanja laserske svetlosti u analizi dinamike i strukture biološke materije. U zavisnosti od oblika, veličina i medjusobne interakcije rasejavača, sredina se modeluje na različite načine. Proučavanjem problema rasejanja svetlosti u biološkim sredinama pojavljuje se potreba za razmatranjem dva krajnja slučaja u kojima se analiziraju centri rasejanja kao nezavisni, i slučajevi kod kojih postoji interakcija. U tom slučaju korelacione funkcije se eksplctitno ne mogu izbeći. Među– slučajevi (između pomenuta dva krajnja) se razmatraju u raznim stepenima interakcija među centrima; problem modelovanja postaje znatno složeniji. U radu je redstavljen jedan način modelovanja ansambla rasejavača biološke sredine čiji se oblik može smatrati cilindričnim. Ovakav model je primenljiv na veliki broj bioloških sistema u kojima su rasejavači svetlosti razni mikroorganizmi, (bakterije, virusi, gljivice i dr), ili pak, neki drugi elementi živih tkiva.Biomedic and biologic media consist on a large number of particles with different dimensions and shapes representing potential laser light scattering centers in analyse of dynamics and structure of biologic substance. Dependence on shape, dimensions and mutual interactions of scatterers medium is modelled in various ways. The studing some problems of light scattering light in biological media has to be considered as two boundary major cases: the analyses of independent centres of scattering, and the case where the centres are mutualy dependent objects. In such case correlation functions are explicite non avoidable. The cases between the major two, are considered on different levels of interaction between centres; modelling roblem becomes more complex. Modelling of the scatterrers ansamble in biological media where the the cyilindrical geometry is in case is anaysed in this paper. This model could be applied to many biological systems where the scatterrers are different microorganisms (bacteria, viruses, micose etc.), or some other parts of the living tissue

Rasejanje svetlosti i tehnike u biološkim i biomedicinskim problemima

Biološke i biomedicinske sredine sadrže veliki broj čestica različitog oblika i veličine koje predstavljaju potencijalne centre rasejanja laserske svetlosti u analizi dinamike i strukture biološke materije. U zavisnosti od oblika, veličina i medjusobne interakcije rasejavača, sredina se modeluje na različite načine. Proučavanjem problema rasejanja svetlosti u biološkim sredinama pojavljuje se potreba za razmatranjem dva krajnja slučaja u kojima se analiziraju centri rasejanja kao nezavisni, i slučajevi kod kojih postoji interakcija. U tom slučaju korelacione funkcije se eksplctitno ne mogu izbeći. Među– slučajevi (između pomenuta dva krajnja) se razmatraju u raznim stepenima interakcija među centrima; problem modelovanja postaje znatno složeniji. U radu je redstavljen jedan način modelovanja ansambla rasejavača biološke sredine čiji se oblik može smatrati cilindričnim. Ovakav model je primenljiv na veliki broj bioloških sistema u kojima su rasejavači svetlosti razni mikroorganizmi, (bakterije, virusi, gljivice i dr), ili pak, neki drugi elementi živih tkiva.Biomedic and biologic media consist on a large number of particles with different dimensions and shapes representing potential laser light scattering centers in analyse of dynamics and structure of biologic substance. Dependence on shape, dimensions and mutual interactions of scatterers medium is modelled in various ways. The studing some problems of light scattering light in biological media has to be considered as two boundary major cases: the analyses of independent centres of scattering, and the case where the centres are mutualy dependent objects. In such case correlation functions are explicite non avoidable. The cases between the major two, are considered on different levels of interaction between centres; modelling roblem becomes more complex. Modelling of the scatterrers ansamble in biological media where the the cyilindrical geometry is in case is anaysed in this paper. This model could be applied to many biological systems where the scatterrers are different microorganisms (bacteria, viruses, micose etc.), or some other parts of the living tissue

The Application of Laser Beam Diffraction and Scattering Methods in the Measurement of Shape and Determination of Material Parameters

Lasers can be used for many applications including determination of size, in addition to the theory of diffraction and material dispersion phenomena. In this paper we calculated the corrections in angular intensity for the Gaussian and uniform particle distributions, the scattering intensity on cylindrical objects. We also evaluated the necessary mathematical summations. In addition, we analyse and simulated the special positions of detectors using laser Doppler anemometric (LDA) methods, which can be used to determine the particle diameter. The dispersion measurements for actual fibres are given at the end. The geometric and material parameters of these fibres were taken before the evaluation of the angular scattering intensity.This is the peer-reviewd version of the article: Srećković, M.; Tomić, Z.; Stank, O. M.; Ilić, J.; Bundaleski, N.; Sekulić, R. S.; Vlada, M. The Application of Laser Beam Diffraction and Scattering Methods in the Measurement of Shape and Determination of Material Parameters. Lasers in Engineering 2007, 17 (3–4), 179–196

The Application of Laser Beam Diffraction and Scattering Methods in the Measurement of Shape and Determination of Material Parameters

Lasers can be used for many applications including determination of size, in addition to the theory of diffraction and material dispersion phenomena. In this paper we calculated the corrections in angular intensity for the Gaussian and uniform particle distributions, the scattering intensity on cylindrical objects. We also evaluated the necessary mathematical summations. In addition, we analyse and simulated the special positions of detectors using laser Doppler anemometric (LDA) methods, which can be used to determine the particle diameter. The dispersion measurements for actual fibres are given at the end. The geometric and material parameters of these fibres were taken before the evaluation of the angular scattering intensity.This is the peer-reviewd version of the article: Srećković, M.; Tomić, Z.; Stank, O. M.; Ilić, J.; Bundaleski, N.; Sekulić, R. S.; Vlada, M. The Application of Laser Beam Diffraction and Scattering Methods in the Measurement of Shape and Determination of Material Parameters. Lasers in Engineering 2007, 17 (3–4), 179–196

Broadband cooling spectra of hot electrons and holes in PbSe quantum dots

Understanding cooling of hot charge carriers in semiconductor quantum dots (QDs) is of fundamental interest and useful to enhance the performance of QDs in photovoltaics. We study electron and hole cooling dynamics in PbSe QDs up to high energies where carrier multiplication occurs. We characterize distinct cooling steps of hot electrons and holes and build up a broadband cooling spectrum for both charge carriers. Cooling of electrons is slower than of holes. At energies near the band gap we find cooling times between successive electronic energy levels in the order of 0.5 ps. We argue that here the large spacing between successive electronic energy levels requires cooling to occur by energy transfer to vibrational modes of ligand molecules or phonon modes associated with the QD surface. At high excess energy the energy loss rate of electrons is 1–5 eV/ps and exceeds 8 eV/ps for holes. Here charge carrier cooling can be understood in terms of emission of LO phonons with a higher density-of-states in the valence band than the conduction band. The complete mapping of the broadband cooling spectrum for both charge carriers in PbSe QDs is a big step toward understanding and controlling the cooling of hot charge carriers in colloidal QDs