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- Resonant energy transfer in Si Nanocrystal SolidsPublication . Limpens, Rens; Lesage, Arnon; Stallinga, Peter; Poddubny, Alexander N.; Fujii, Minoru; Gregorkiewicz, TomEnergy exchange between closely packed semiconductor quantum dots allows for long-range transfer of electronic energy and enables new functionalities of nanostructured materials with a huge application potential in photonics, optoelectronics, and photovoltaics. This is illustrated by impressive advances of quantum-dot solids based on nanocrystals (NCs) of direct bandgap materials, where this effect has been firmly established. Regretfully, the (resonant) energy transfer in close-packed ensembles of NCs remains elusive for silicon the main material for electronic and photovoltaic industries. This is the subject of the present study in which we conclusively demonstrate this process taking place in dense dispersions of Si NCs in an SiO2 matrix. Using samples with different NC configurations, we can directly determine the wavelength dependent energy transfer rate and show that it (i) can be modulated by material parameters, and (ii) decreases with the NCs size, and thus being consistent with the energy flow proceeding from smaller to larger NCs. This result opens the way to new applications of Si NCs, requiring energy transport and extraction. In particular, it forms a fundamental step toward development of an excitonic all-Si solar cell, operating in some analogy to polymer devices.
- Knowledge-based economyPublication . Stallinga, Peter; Fonseca, Custódia; Khmelinskii, IgorThe European Union is resorting to long-term multi-annual political and economical plans. The current set of plans, “Horizons 2020”, also involves restructuring the educational system, as in the Bologna system. The idea behind it is that education should help industry to win the competitive battle with other major economical blocks. The idea is best described by the adage of the European Union of developing a so-called “knowledge-based economy”. It implies that education is a form of investment. We should educate people – the society should spend effort on educating people – in order for society to make profit on it. Contrasting this is the idea of education as a consumption good. In the latter, people study to become knowledgeable, since knowledge makes a person happy. We discuss here the dissident view why an educational system that is for investment-only will at the end not bear fruit and will destroy science, creativity and eventually any form of competitiveness in the economy. It will lead to moral as well as financial bankruptcy.
- Relationship between education in pharmaceutical sciences and profession: an interdisciplinary perspective" Book of Proceedings II International Congress on Interdisciplinarity in Social and Human SciencesPublication . Fonseca, Custódia; Stallinga, Peter; Khmelinskii, IgorThe first modern-era pharmacy schools began to be established in the nineteenth century, with some universities offering degrees or similar-level courses. However, the traditional pharmaceutical education continued in parallel, in the form of apprenticeships and “on the job” experience. The decline of manufacturing in pharmacies, caused by the development of pharmaceutical industry, and the ensuing advisory role of pharmacists led to additional educational reforms in the last 50 or so years. Subjects such as anatomyphysiology, physiopathology and pharmacotherapy were incorporated into the pharmacy courses, which became longer. This reflected the growing body of relevant knowledge and the perceived need to increase the capacity of pharmacists to act as pharmacy-therapeutic advisors to both health professionals and general public. The degrees offered now include Doctorates in Pharmaceutical Sciences as well as Masters and Integrated Masters (IM). The typical duration of an undergraduate degree in Portugal (IM) is now five years. Pharmacists may now receive instruction in social disciplines, such as health psychology, economics and public health. Students should be prepared for lifelong learning, since their formal training cannot provide them with all that they will need in future, thus each individual pharmacist is personally responsible for ‘the maintenance, development and broadening of knowledge, skills and attitudes, to ensure competence as a professional, throughout their career’. The present communication describes the structure of the Pharmaceutical Sciences degree in Portugal, satisfying the needs of the labour market in such health professionals.
- Carrier multiplication in germanium nanocrystalsPublication . Saeed, Saba; de Weerd, Chris; Stallinga, Peter; Spoor, Frank C. M.; Houtepen, Arjan J.; Siebbeles, Laurens D. A.; Gregorkiewicz, TomCarrier multiplication is demonstrated in a solid-state dispersion of germanium nanocrystals in a silicon-dioxide matrix. This is performed by comparing ultrafast photo-induced absorption transients at different pump photon energies below and above the threshold energy for this process. The average germanium nanocrystal size is approximately 5-6 nm, as inferred from photoluminescence and Raman spectra. A carrier multiplication efficiency of approximately 190% is measured for photo-excitation at 2.8 times the optical bandgap of germanium nanocrystals, deduced from their photoluminescence spectra.
- Optical excitation and external photoluminescence quantum efficiency of Eu3+ in GaNPublication . de Boer, W. D. A. M.; McGonigle, C.; Gregorkiewicz, Tom; Fujiwara, Y.; Tanabe, S.; Stallinga, PeterWe investigate photoluminescence of Eu-related emission in a GaN host consisting of thin layers grown by organometallic vapor-phase epitaxy. By comparing it with a reference sample of Eu-doped Y2O3, we find that the fraction of Eu3+ ions that can emit light upon optical excitation is of the order of 1%. We also measure the quantum yield of the Eu-related photoluminescence and find this to reach (similar to 10%) and (similar to 3%) under continuous wave and pulsed excitation, respectively.
- Education today: 12 + 5 < 4 - lessons of education reforms in Portugal and beyondPublication . Khmelinskii, Igor; Fonseca, Custódia; Stallinga, PeterSince the adoption of the ‘Lei de Bases…’ of 1984, the quality of education in Portugal is declining, undermined by ‘critical, creative and independent thinking’, implemented by neglecting memorization as a learning tool, as supposedly students should understand things without knowing them. As a consequence, vast majority of students can’t retain any abstract knowledge. They prepare from scratch for their tests and forget everything afterwards. The students never acquire essential primary-school skills such as capacity to do mental calculations, hence the title of this report, comparing contemporary school + university education to pre-1984 primary school of 4 years. The quality of education is further degraded by ‘evaluation’ of teachers at school and university, judged by academic success and degree of satisfaction of their students. With the students objectively incapable to learn, understand or remember, the teachers have a dilemma of either letting such students pass without retained knowledge, skills and competences, or else have their own ‘evaluation’ suffer. As the generations change, students who were ‘passed’ become teachers themselves, still with no retained knowledge and thus no moral authority to fail their own students. Thus, the level of requirements monotonously degrades, with the educational fraud perpetuated in the new generations.