Decoherence and Quantum Interference assisted electron trapping in a quantum dot

We present a theoretical model for the dynamics of an electron that gets trapped by means of decoherence and quantum interference in the central quantum dot (QD) of a semiconductor nanoring (NR) made of five QDs, between 100 K and 300 K. The electron's dynamics is described by a master equation with a Hamiltonian based on the tight-binding model, taking into account electron-LO phonon interaction (ELOPI). Based on this configuration, the probability to trap an electron with no decoherence is almost 27%. In contrast, the probability to trap an electron with decoherence is 70% at 100 K, 63% at 200 K and 58% at 300 K. Our model provides a novel method of trapping an electron at room temperature.Comment: Revtex 4, 11 pages, 13 figure

How is Modernity Accepted by Consumers with Respect to Traditional Food Products? The Case of Traceability

Up till now, no researches have been done on consumers’ acceptability of new technical supporters of traceability, especially for traditional food products. Therefore, in the framework of the EU research project TRACE, we carried out focus group discussions, individual laddering interviews (with hierarchical value maps) and a choice-based conjoint experiment. Traceability is a fashionable word with different meanings whether it comes to producers or to consumers. The formers link it to technical aspects while the latter see in it a path for safe and good quality food products. How to intersect these two dimensions when advertising trend and consumer expectations are focusing on traditional food products? In France, consumers are familiar with the word traceability, however, they are not aware of the new supports of food traceability. They are still not ready for sophisticated systems and prefer the labeling ones. The more abstract the traceability support is, the more complex traceability seems to be perceived by them. Interestingly, we questioned consumers on traceability supports, they mainly responded on origin and label of origin as a simple way to track food products. This indicates that traditional origin labeled food products are considered as naturally tracked, while industrial products are perceived to come from a less identifiable source, and are better accepted with the guarantee of brand.Traceability supports, traditional, consumers, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety,

Consumers' perception of food traceability in Europe

Food traceability has become mandatory since 1st January 2005 in the European Union. Traceability of products and activities in the supply chain has become a new factor of competitiveness in agribusiness and is deemed to be an important criterion of perception of food product quality and safety for consumers. This paper has three objectives: i) to get a deeper understanding of the role of the "ability-to- trace" in consumer decision- making process with respect to food, ii) to measure consumers' acceptability for food traceability, iii) to check the differences of these matters across twelve European countries in order to highlight any specificity. The purpose is based on the analysis of the verbatim recorded within twenty four focus groups discussions carried- out in autumn 2005.Food Traceability, Consumer Attitudes, Focus Groups, European Countries, Food Consumption/Nutrition/Food Safety,

Incoherent lensless imaging via coherency back-propagation

The two-point complex coherence function constitutes a complete representation for scalar quasi-monochromatic optical fields. Exploiting dynamically reconfigurable slits implemented with a digital micromirror device, we report on measurements of the complex two-point coherence function for partially coherent light scattering from a `scene' comprising one or two objects at different transverse and axial positions with respect to the source. Although the intensity shows no discernible shadows in absence of a lens, numerically back-propagating the measured complex coherence function allows estimating the objects' sizes and locations -- and thus the reconstruction of the scene.Comment: 4 pages, 4 figure

Division of Metabolic Engineering

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A Curricula Assessment And Improvement Quantitative Model For Higher Education: A Design For Six Sigma Methodology

Curricula assessment is an integrated process to assist higher education institutions in addressing the challenges in a designated field of study and in exploring the opportunities to better educate and prepare their students for an increasingly complex world. Although assessment as a topic has been researched extensively, there has been a lack of quantitative tools that address the requirements of many of the stakeholders that may be critical to the curriculum design and assessment processes. This research proposes the utilization of Design for Six Sigma (DFSS) to develop a quantitative model for curriculum assessment and improvement for higher education institutions. A review of the literature indicates that there is a lack of quantitative tools that enhance the reliability and efficiency of gathering customer requirements for curriculum in higher education environment. In addition, there is a lack of tools to translate these requirements into actual characteristics that can be used for curriculum design and assessment purposes. The literature also indicates that curriculum assessment is one of several educational processes that affect the quality of education. This research proposes a quantitative model for curriculum assessment and improvement in higher education institutions, utilizing design for six sigma methodology. The proposed model explores the use of the Kano model concept to translate needed requirements into desirable curriculum attributes and the general concept of establishing transfer function to determine the level at which those requirements have been satisfied. The use of the developed model can help improve student learning and provide curriculum stakeholders with timely feedback about the curriculum and identify areas in need of improvement. To validate the capability of the proposed model, an ABET accredited department of Industrial Engineering in a US university was used a case study

Optical Parity Time Metasurface Structures

In the last few years, optics has witnessed the emergence of two fields namely metasurfaces and parity-time (PT) symmetry. Optical metasurfaces are engineered structures that provide unique responses to electromagnetic waves, absent in natural materials. Optical metasurfaces are known for their reduced dimensionality i.e. subwavelength and consequently lower losses are anticipated. The other paradigm is the PT symmetric materials, also known as photonic synthetic matter. PT symmetry has emerged from quantum mechanics when a new class of non-Hermitian Hamiltonian quantum systems was highlighted to have real eigenvalues, hence eradicating Hermiticity of the Hamiltonian as an essential condition to the existence of real eigenvalues. The first half of the thesis is focused on the experimental and numerical realization of PT symmetric metasurfaces. A systematic methodology is developed to implement this class of metasurfaces in both one-dimensional and two-dimensional geometries. In two dimensional systems, PT symmetry can be established by employing either H-like diffractive elements or diatomic oblique Bravais lattices. It is shown that the passive PT symmetric metasurfaces can be utilized to appropriately engineer the resulting far-field characteristics. Such PT-symmetric structures are capable of eliminating diffraction orders in specific directions, while maintaining or even enhancing the remaining orders. Later, it is shown a first ever attempt of PT metasurface fabricated on a flexible polymer (polyimide) substrate. The studied PT metasurface exhibits the ability to direct light, i.e. Poynting vector in a desired direction. Herein, the light scattered from the fabricated device in the undesired direction is attenuated by at least an order of magnitude. The proposed PT symmetric metasurface is essentially diatomic Honeycomb Bravais lattice, where both the passive and lossy elements exist side by side on each site separated by 50 nm. The unidirectionality of the studied metasurface is not limited to a single wavelength, on the contrary, it is observed to be effective on the entire visible band (400 – 600 nm). The PT symmetric meatsurface is also fabricated on a high strength substrate; sapphire (Al2O3). An excellent agreement between the experimental and numerical (COMSOL) results is found for both substrates. Customized modifications to the current design can open avenues to study the unidirectionality of metasurfaces to different optical bands, for example IR. The second part of the thesis deals with the theoretical modeling of the dynamics of an electron that gets trapped by means of decoherence and quantum interference in the central quantum dot (QD) of a semiconductor nanoring (NR) made of five QDs, between 100 and 300 K. The electron\u27s dynamics is described by a master equation with a Hamiltonian based on the tight-binding model, taking into account electron–LO phonon interaction. Based on this configuration, the probability to trap an electron with no decoherence is almost 27%. In contrast, the probability to trap an electron with decoherence is 70% at 100 K, 63% at 200 K and 58% at 300 K. Our model provides a novel method of trapping an electron at room temperature. This setup is then used to propose a theoretical model for an electrically driven single photon source operating at high temperatures. It is shown that the decoherence, which is usually the main obstacle for operating single photon sources at high temperatures, ensures an efficient operation of the presented electrically driven single photon source at high temperatures. The single-photon source is driven by a single electron source attached to a heterostructure semiconductor nanoring. The electron\u27s dynamics in the nanoring and the subsequent recombination with the hole is described by the generalized master equation with a Hamiltonian based on tight-binding model, taking into account the electron-LO phonon interaction. As a result of decoherence, an almost 100% single photon emission with a strong antibunching behavior i.e. g(2)(0) \u3c \u3c 1 at high temperature up to 300 K is achieved

Primary GC-MS chemical analysis of alcoholic extract of Emex spinosa (L.) Campd. and screening of their antioxidant, antibacterial, and cytotoxic characteristics

ABSTRACT. The chemical constituents of the methanolic extract of Emex spinosa shoots were primarily characterized by gas-chromatography-mass spectrometry analysis (GC-MS), forty components were identified. The major components were ethyl 2-hydroxycyclohexane-1-carboxylate (10.11%), 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one (38.09%), 2-propyltetrahydro-2H-pyran-3-ol (5.75%), oleic acid (8.02%), and methyl (E)-octadec-16-enoate (5.91%). The results of antioxidant activity of leaves extract presented the most potent activity (IC50 = 29.92 mg mL-1), followed by stem extract (IC50 = 41.17 mg mL-1), and root extract (IC50 = 50.14 mg mL-1), comparable to that of the standard ascorbic acid (IC50 = 13.3 mg mL-1). The antibacterial results revealed that leaves extract is the most potent (22.0 mm) antibacterial agent against the variety of the tested species. Stem and leaves extracts are more potent (20 and 20 mm, respectively) than azithromycin (13.0 mm) against Pseudomonas aeruginosa species, while root and leaves extracts displayed potent antibacterial activities than tetracycline (10 mm). The most potent activity was recorded for leaves extract against Bacillus cereus species (22.0 mm) higher than the standard antibiotics (5.0-20.0 mm). The cytotoxic activity of E. spinosa MeOH extract specified the EC50 value at 2.68 µg mL-1 attended by a cytotoxic effect on HepG2 cell lines with the effective dose of the plant extract at a higher concentration.                                                                      KEY WORDS: Emex spinosa, GC-MS, Antioxidant, Antibacterial, Cytotoxic activities   Bull. Chem. Soc. Ethiop. 2023, 37(1), 101-114.                                                              DOI: https://dx.doi.org/10.4314/bcse.v37i1.9                                                       &nbsp