1,827 research outputs found

    La enseñanza-aprendizaje del español como lengua extranjera en Rumanía. Análisis de la situación y propuesta de mejora

    Full text link
    [ES] El auge de la lengua española en muchos países es indudable y esto impulsa la investigación de su enseñanza y aprendizaje. Son múltiples los estudios realizados (Fernández Saavedra y Gómez, 2010; Fondo y Gago, 2022; Manzanares, 2020; Merziq, 2022; Rabadán y Orgambídez, 2018; Rodríguez García, 2022) en diferentes contextos educativos y sus aportaciones y relevancia son de suma importancia para la didáctica de las lenguas. Ante el cambio constante y acelerado en el mundo, principalmente en los ámbitos económico, social y tecnológico, mejorar la actuación docente supone muchos beneficios para la sociedad. Permite formar al estudiantado para su futuro laboral, así como promover el uso de tendencias pedagógicas actuales y plantear nuevas propuestas adaptadas a las demandas de la sociedad. La presente tesis doctoral tiene como objetivo general investigar la situación actual de la enseñanza-aprendizaje del español como lengua extranjera en Rumanía a nivel de secundaria y de universidad para detectar necesidades y carencias y ofrecer propuestas pedago-didácticas innovadoras, aplicables al aula. Para conseguirlo, primero se hace una incursión teórica en los métodos de enseñanza-aprendizaje y en la evolución del español en Rumanía. Después, la metodología de investigación adopta un enfoque mixto de recogida de datos basado en técnicas cuantitativas y cualitativas. Se recolecta información acerca de las características, creencias, necesidades y dificultades del profesorado y alumnado rumano de secundaria superior y universitario. Se trabaja con una muestra de 60 docentes y 470 estudiantes de diferentes centros educativos del país. Los datos se analizan estadística y manualmente. En base a ello se diseñan dos propuestas de mejora: una guía de buenas prácticas basada en las tendencias pedagógicas actuales y un proyecto formativo para el profesorado de Español Lengua Extranjera (ELE). Su implementación en la realidad educativa rumana se lleva a la práctica utilizando dos vías: la guía se aplica a un grupo clase de 23 estudiantes universitarios de la Universidad Babe¿-Bolyai de Cluj-Napoca y el proyecto formativo se da a conocer entre los docentes del país y se difunde bajo la forma de Encuentros virtuales a nivel nacional e internacional. Los resultados obtenidos revelan la necesidad de un cambio en el sistema educativo y en la metodología docente para adaptarse a los intereses de los actuales aprendientes. Asimismo, ponen de manifiesto el requisito del profesorado de formarse en las tendencias actuales de enseñanza-aprendizaje. Las propuestas responden a los deseos expresados y consiguen motivar al estudiantado y entusiasmar a los docentes. Las conclusiones evidencian los beneficios que reporta la presente tesis doctoral a la comunidad educativa y científica, transferibles a contextos educativos similares.[CA] L'auge de la llengua espanyola en molts països és indubtable i això impulsa la investigació del seu ensenyament i aprenentatge. Són múltiples els estudis realitzats (Fernández Saavedra i Gómez, 2010; Fons i Gago, 2022; Manzanares, 2020; Merziq, 2022; Rabadán i Orgambídez, 2018; Rodríguez García, 2022) en diferents contextos educatius i les seues aportacions i rellevància són de summa importància per a la didàctica de les llengües. Davant el canvi constant i accelerat en el món, principalment en els àmbits econòmic, social i tecnològic, millorar l'actuació docent suposa molts beneficis per a la societat. Permet formar a l'estudiantat per al seu futur laboral, així com promoure l'ús de tendències pedagògiques actuals i plantejar noves propostes adaptades a les demandes de la societat. La present tesi doctoral té com a objectiu general investigar la situació actual de l'ensenyament-aprenentatge de l'espanyol com a llengua estrangera a Romania a nivell de secundària i d'universitat per a detectar necessitats i mancances i oferir propostes pedago- didàctiques innovadores, aplicables a l'aula. Per a aconseguir-ho, primer es fa una incursió teòrica en els mètodes d'ensenyament-aprenentatge i en l'evolució de l'espanyol a Romania. Després, la metodologia d'investigació adopta un enfocament mixt de recollida de dades basat en tècniques quantitatives i qualitatives. Es recol·lecta informació sobre les característiques, creences, necessitats i dificultats del professorat i alumnat romanés de secundària superior i universitari. Es treballa amb una mostra de 60 docents i 470 estudiants de diferents centres educatius del país. Les dades s'analitzen estadística i manualment. Sobre la base d'això es dissenyen dues propostes de millora: una guia de bones pràctiques basada en les tendències pedagògiques actuals i un projecte formatiu per al professorat d'Espanyol Llengua Estrangera (ELA). La seua implementació en la realitat educativa romanesa s'emporta a la pràctica utilitzant dues vies: la guia s'aplica a un grup classe de 23 estudiants universitaris de la Universitat Babe¿-Bolyai de Cluj-Napoca i el projecte formatiu es dona a conéixer entre els docents del país i es difon sota la forma de Trobades virtuals a nivell nacional i internacional. Els resultats obtinguts revelen la necessitat d'un canvi en el sistema educatiu i en la metodologia docent per a adaptar-se als interessos dels actuals aprendientes. Així mateix, posen de manifest el requisit del professorat de formar-se en les tendències actuals d'ensenyament- aprenentatge. Les propostes responen als desitjos expressats i aconsegueixen motivar a l'estudiantat i entusiasmar als docents. Les conclusions evidencien els beneficis que reporta la present tesi doctoral a la comunitat educativa i científica, transferibles a contextos educatius similars.[EN] The increased interest in studying Spanish as a Foreign Language in numerous countries is unquestionable and thus encourages us to research peculiarities about its teaching and learning. Multiple investigations (Fernández Saavedra y Gómez, 2010; Fondo y Gago, 2022; Manzanares, 2020; Merziq, 2022; Rabadán y Orgambídez, 2018; Rodríguez García, 2022) have been conducted in different educational contexts and their contributions and relevance are of the utmost importance for language teaching. Given the constant and rapid changes in the world, mainly in the economic, social and technological fields, improving teaching performance brings a number of benefits into our society. It allows the student body to be trained for its future inclusion in the labor market, but also promotes the use of current pedagogical trends and proposes new programmes adapted to the demands of the society. The general objective of this doctoral thesis is to investigate the current situation of the process of teaching-learning Spanish as a foreign language in Romania in both secondary and university levels in order to detect needs and deficiencies and offer innovative pedagogical and didactic proposals, applicable to the classroom. To achieve this, first a theoretical incursion is made into the teaching-learning methods and the evolution of Spanish in Romania. Then, the research methodology adopts a mixed approach to data collection based on quantitative and qualitative techniques. Information is collected about the characteristics, beliefs, needs and difficulties of Romanian upper secondary and university teachers and students. A sample of 60 teachers and 470 students from different educational centers in the country was used. The data is statistically and manually analyzed. Based on this, two proposals for improvement are designed: a guide to good practices based on current pedagogical trends and a training project for teachers of Spanish as a Foreign Language (ELE). Its implementation in the Romanian educational context is put into practice using two approaches: the guide is applied to a class group of 23 university students from the Babe¿-Bolyai University of Cluj-Napoca and the training project is made known amongst teachers in the country and is disseminated in the form of virtual meetings at the national and international level. The results obtained reveal the need for a change in the educational system and in the teaching methodology in order to adapt to the interests of current learners. Likewise, they highlight the requirement of teachers to be trained in the current teaching-learning trends. The proposals are based on the highlighted requests and advise to motivate the students and enthuse the teachers. The conclusions demonstrate the benefits that this doctoral thesis reports to the educational and scientific community and how they are transferable to similar educational contexts.Stînga, PA. (2023). La enseñanza-aprendizaje del español como lengua extranjera en Rumanía. Análisis de la situación y propuesta de mejora [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/20155

    Design of an interferometric system for gauge block calibration

    Get PDF
    We have developed an interferometer for gauge block calibration based on phase shifting algorithms. The measurement process can provide flatness, parallelism, and length. Wavelength values need to be corrected according to the refractive index of air. This correction is obtained indirectly using Edlén’s equation. High-resolution sensors provide the temperature, pressure, and relative humidity readings. To preserve stability, the interferometer is encapsulated in a chamber with active temperature control. Its design, measurement principle, calibration, stability, and reproducibility are analyzed. Since one goal is to employ robust and cheap diode lasers as light sources, we describe the system developed to stabilize a red laser diode using a mode locking technique with a reference gas cell. The instruments and assembly are used to avoid the Doppler effect in the gas cell, which would limit wavelength resolution. Several experiments are carried out to restrict the influence of environmental changes, which affect laser diode frequency.Ministerio de Educación y Ciencia | Ref. DPI2008-06818-C2-0

    Studies and Cooling of Highly Charged Ion Ensembles in the ARTEMIS Trap and High-Precision Mass Measurements of 221Fr, 219Rn, 213Bi, 211Pb, 209Pb, 207Tl and 207Pb at SHIPTRAP

    Get PDF
    Penning traps open up unique experimental possibilities for mass spectrometry and spectroscopy of atomic ions with high precision. Two such experiments based on Penning traps are SHIPTRAP and ARTEMIS at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt. The ARTEMIS experiment is designed to measure the magnetic moment (g-factor) of an electron in heavy, highly charged ions at the 10−9 level, by the means of laser-microwave double-resonance spectroscopy. Such measurements represent highly stringent tests of QED in extreme fields. The ion of choice for the demonstration and development of the experimental methods is 40Ar13+, which can be produced internally in the trap, for later measurements 209Bi82+ is foreseen. For each of the measurements, the preparation of a cleaned and cooled cloud of ions in the spectroscopy trap is necessary. In this work, the system is optimised for non-destructive detection and cooling of the ions, and production, transport, cooling, selection and storage of the Ar13+ ions are systematically demonstrated. Precision mass measurements of the long-lived decay products of 225Ac and 223Ra are carried out at SHIPTRAP, using the phase-imaging ion-cyclotron-resonance technique. The masses of 221Fr, 219Rn, 213Bi, 211Pb, 209Pb, 207Tl and 207Pb are measured with a relative precision of 10−9, allowing an increase in the accuracy of other masses in this region. Some of these masses find direct input into the g-factor measurements, such as in the case of 209Bi, which is of interest to ARTEMIS. Furthermore, the doublet 205Tl / 205Pb, which is of great significance in nuclear astrophysics, is also linked to the measured masses

    A high-flux cold atom source based on a nano-structured atom chip

    Get PDF
    Modern physics is challenged by existential questions about the most fundamental interactions of matter. While three of the four known fundamental forces are modeled in the grand unified theory [1], gravity seems to be incompatible in its current formulation. Many physicists search to unify them, but often the invented models violate well-tested assumptions such as the Einstein Equivalence Principle, a cornerstone of General Relativity. Despite macroscopic tests of this principle have already been carried out to high precision [2–4], quantum tests exploiting matter-wave interferometry [5–7] may provide complementary information [8] with even higher precision [9–11]. These yield their ultimate performance with Bose-Einstein condensates (BECs) over long evolution times as conventionally achieved by free-fall in space [12]. As such, a new generation of high performance BEC sources is required with strict budgets on size, weight and power demands. Efforts to miniaturize these sources have been pursued with promising results using atom chips [13–15], but further miniaturization of these setups is necessary. In an attempt to simplify the usage of atom chips, the following thesis describes the development of a nano-structured atom chip that allows for single-beam magneto-optical trapping. The chip is implemented in a dedicated atom chip test facility that has been planned, built and characterized in the scope of this thesis. The facility features a state-of-the-art master oscillator power amplifier laser system, compact control electronics [13,15–17] and a high-flux 2D+-MOT as an atomic source. Despite the simplified setup, magneto-optical trapping of 1.1 × 10^9 Rubidium atoms was achieved within 1 s which is comparable to other atom chip setups and well above previous achievements with grating MOTs [18–23]. Illuminating the grating with a beam profile from a custom-built top-hat beam expander was instrumental to achieve balanced laser cooling in a large volume above the grating. This allowed to cool 4.7 × 10^8 atoms to 13 µK and transfer 2.4 × 10^8 atoms into a large-volume Ioffe-Pritchard type magnetic chip trap, demonstrating the required mode-matching between the laser cooled atoms and the magnetic trap. The trapped atoms were then used to characterize the magnetic field environment of the test facility using radio frequency spectroscopy gauging the surrounding magnetic bias coils. These results demonstrate the feasibility of using a nano structured atom chip to build a single-beam BEC source which could become the foundation of future high-performance quantum sensors on ground and in space

    Towards a novel platform for imaging molecules in an optical lattice

    Get PDF
    This thesis reports on the development of a new apparatus which will be used to produce rovibrational ground state molecules with the goal of imaging them in an optical lattice. These types of experiments are often referred to as quantum gas microscopes. The two molecules which we wish to study are RbCs and KCs. RbCs has been already studied substantially at Durham but not in an apparatus as advanced as the one discussed in this thesis. RbCs and other ground state diatomic molecules may be formed in the rovibrational ground state by us- ing a magnetoassociation on an interspecies Feshbach resonance followed by stimulated Raman adiabatic passage (STIRAP). In our new apparatus we plan to repeat this in an optical lattice positioned directly above an object- ive with a high numerical aperture which will have the capability to resolve single lattice sites. Loading molecules into an optical lattice will allow access to dipolar physics associated with the intrinsic electric dipole moment of the molecule. This will grant us the capability to perform experiments, such as quantum simulation, that can yield a deeper understanding of the quantum nature of matter confined in lattices. In addition we show work towards KCs molecules, of which ground state molecules are yet to be formed. This molecule has a dipole moment of 1.92 D and a stable fermionic isotope which makes it a promising candidate for our studies in addition to RbCs. A new vacuum chamber apparatus is constructed. A pair of 2-dimensional magneto-optical traps (2D-MOTs), one for Cs and the other for K/Rb, provides a flux of atoms to the centre of our main vacuum chamber. Here the atoms are collected in a 3D-MOT. The 3D-MOT can accumulate 108 Cs atoms, 109 Rb atoms and 108 K atoms. The laser setups for our MOTs are also presented in this thesis. We laser cool Rb, Cs and K on their respective D2 transitions. There is a particular focus on the optimisation process of K. We have managed to cool a sample of 108 K atoms to 42(2) μK and obtain a simultaneous MOT of both K and Cs. We have potential plans to further cool K on the D1 line. To achieve this we need some means of high quality frequency stabilisation so a study on the modulation transfer spectroscopy of K and a comparison against the associated theory is also presented in this thesis. Using a moving optical standing wave the atoms are transported to the science cell. They will subsequently undergo various cooling stages until the phase space density is sufficiently high for magnetoassociation. This has been achieved with Rb and Cs but not yet for K and Cs. They will then be loaded into an optical lattice and associated into molecules. STIRAP requires lasers frequency stabilised to less than a kHz. The STIRAP setup is also described in detail in this thesis. We lock two lasers of wavelength 895 nm and 1359 nm to an ultra low expansion cavity and demonstrate proof of concept of how such a setup can serve the dual purpose of both STIRAP for KCs molecules and for exciting Cs atoms to Rydberg states using the Cs D1 transition

    Assessment of high school students in computer science education

    Get PDF
    The thesis concerns the assessment and evaluation of secondary school students in computer science subjects in the Information Technology 18-20-M/01 field of study in the Czech Republic. There is no methodology readily available for the teachers of informatics-oriented subjects to assess and evaluate students, and the teachers adapt the assessment to their own needs as well as the conditions of the particular school. The aim of the theoretical part of the thesis is to introduce the issue of assessment and evaluation, based on the analysis of literature on the issue of school assessment and evaluation at secondary schools in IT-oriented subjects. The theoretical part of the thesis describes theoretical knowledge in the field of student assessment and evaluation. The possibilities and types of assessment and evaluation, together with methodological approaches to those, are presented, along with their use, advantages, and disadvantages. The findings are supported by professional literature, and further interpreted. The aim of the practical part is to observe how teachers evaluate students in IT-oriented subjects, what methods and approaches they apply in individual subjects, how they approach the evaluation of the learning outcomes and their students' work. The research was conducted on n = 63...Diplomová práce se zabývá hodnocením žáků středních škol v informaticky zaměřených předmětech studijního oboru Informační technologie 18-20-M/01 v ČR. Pro informaticky zaměřené předměty není pro učitele k dispozici metodika pro hodnocení žáků a učitelé si hodnocení přizpůsobují vlastním potřebám a podmínkám dané školy. Cílem teoretické části práce je seznámit čtenáře s problematikou hodnocení na základě analýzy odborné literatury k problematice školního hodnocení na SŠ v informaticky zaměřených předmětech. Teoretická část práce popisuje teoretické poznatky v oblasti hodnocení žáků. Seznámíme se s možnostmi a druhy hodnocení, metodickými přístupy k hodnocení, jejich využití, výhody a nevýhody. Tyto poznatky jsou podloženy odbornou literaturou a dále interpretovány. Cílem praktické části je zjistit, jakým způsobem učitelé hodnotí žáky v informaticky zaměřených předmětech, jaké metody a přístupy v jednotlivých předmětech využívají, jak přistupují k hodnocení výsledků učení a práce svých žáků. Výzkum byl proveden mezi n = 63 učiteli SŠ v ČR s použitím dotazníkové metody. Z výsledků výzkumu vyplývá, že v hodnocení žáků přetrvávají starší koncepty hodnocení jako například testování, hodnocení známkami, ale objevují se i moderní koncepty jako je formativní hodnocení, hodnocení výstupů apod. Je důležité,...Katedra informačních technologií a technické výchovyFaculty of EducationPedagogická fakult

    Advances in performance and automation of a single ytterbium ion optical clock

    Get PDF
    While the SI second is currently defined in terms of a microwave transition frequency in caesium, atomic clocks based on an optical transition are currently outperforming caesium clocks by up to two orders of magnitude. In order to fully exploit the potential accuracy achievable by optical clocks, the SI second needs to be redefined in terms of an optical frequency standard. The ¹⁷¹Yb⁺ ion is an excellent candidate thanks to the extremely narrow linewidth of its electric octupole (E3) transition and its particular insensitivity to external perturbations. This thesis is focused on the ytterbium ion optical clock at the National Physical Laboratory (NPL), consisting of a single ¹⁷¹Yb⁺ ion trapped in a radio frequency (RF) Paul trap and probed by ultrastable 467-nm light to excite the E3 transition. Improved measurement methods were developed for the evaluation of several systematic frequency shifts. In particular, the electric quadrupole shift, which used to be the leading source of uncertainty, can now be directly measured with an accuracy in the low parts in 10¹⁸. A great focus was put on the automation of several aspects of the experiment. Because all optical clocks generally require a lot of maintenance and attention during their operation, many experimental routines were automated in order to minimise the requirement for human intervention. Furthermore, the analysis of almost all systematic shifts was automated, requiring minimal manual input so that shifts could be evaluated on the fly. Finally, a generalised framework was developed for the automatic evaluation of the absolute frequency of the optical clock via the International Atomic Time (TAI). In order to increase the confidence in the level of performance of the ytterbium ion optical clock, international clock comparison campaigns are regularly carried out. Between 2019 and 2022, several results were produced: two absolute frequency measurements via TAI with an uncertainty at the 1 × 10⁻¹⁵ level; two local frequency ratio measurements between ¹⁷¹Yb⁺ (E3) and ⁸⁷Sr with an uncertainty in the low parts in 10¹⁷; three uncertainty budgets at the parts in 10¹⁸ level; and one measurement of the ratio of the octupole and quadrupole optical clock transitions in ¹⁷¹Yb⁺ with an uncertainty of 1.5 × 10⁻¹⁶. All of these results are shown to be consistent with each other and in good agreement with the literature. Furthermore, a prototype optically-steered time scale was successfully demonstrated for the first time at NPL with the contribution of both the ¹⁷¹Yb⁺ and ⁸⁷Sr optical clocks.Open Acces

    Precision spectroscopy of the 2S-6P transition in atomic deuterium

    Get PDF
    Die Quantenelektrodynamik (QED) bildet die Grundlage aller anderen Quantenfeldtheorien, auf denen das Standardmodell der Teilchenphysik aufgebaut ist. Derzeit ist klar, dass unser fundamentales Naturverständnis unvollständig ist, sodass erwartet wird, dass das Standardmodell um neue Teilchen oder Wechselwirkungen verändert oder erweitert werden muss. Eine Möglichkeit, diese Grenzen der Grundlagenphysik zu erforschen, ist die Durchführung von Präzisionsmessungen. Diese Arbeit untersucht die Präzisionslaserspektroskopie von Deuterium, wo die Übergangsenergien zwischen verschiedenen Energiezuständen des an den Kern gebundenen Elektrons mit Techniken wie ultrastabilen Lasern und dem Frequenzkamm genau gemessen werden können. Aufgrund der Einfachheit der wasserstoffähnlichen Atome können ihre Energieniveaus anhand der QED-Theorie für gebundene Zustände genau berechnet werden, und mit dem Experiment mit der relativen Genauigkeit in der Größenordnung von 101210^{-12} verglichen werden. Ein solcher Vergleich zwischen Theorie und Experiment ist mit der Bestimmung von Naturkonstanten verbunden, die als Parameter in die Theorie eingehen. Erst wenn mehr unabhängige Messungen als Parameter vorliegen, kann die Theorie überprüft werden. Der Vergleich zwischen Theorie und Laser-Spektroskopie im Deuterium betrifft die Ryd-berg-Konstante RR_\infty und den Deuteronen-Ladungsradius rdr_d. Dies erfordert mindestens zwei Messungen der verschiedenen Übergangsfrequenzen, um diese Konstanten zu bestimmen, und mehr Messungen, um die Theorie zu testen. Im Gegensatz zum Wasserstoff gibt es bei Deuterium nur wenige ausreichend genaue Messungen der Übergänge. In dieser Arbeit wird die erste Untersuchung des 2S-6P-Übergangs in Deuterium vorgestellt, die mit der bestehenden Frequenzmessung des 1S-2S-Übergangs kombiniert werden kann, um RR_\infty und rdr_d zu erhalten. Zusammen mit der Messung des 2S-2P-Übergangs von myonischem Deuterium stellt diese Bestimmung einen Theorietest dar. Ein solcher Vergleich ist wichtig, um die anhaltende Diskrepanz zwischen dem Ergebnis aus myonischem Deuterium und dem Durchschnitt früherer Daten aus elektronischem Deuterium, sowie die Spannungen zwischen den jüngsten Ergebnissen aus der Wasserstoffspektroskopie, zu beleuchten. Im Gegensatz zu Wasserstoff wird die Präzisionsspektroskopie des 2S-6P-Übergangs in Deuterium durch die gleichzeitige Anregung unaufgelöster Hyperfeinstruktur-Komponenten erschwert, was zur unaufgelösten Quanteninterferenz führen kann. Diese Arbeit untersucht die möglichen systematischen Effekte, die mit dieser Komplikation verbunden sind. Zusammen mit analytischen störungstheoretischen Modellen werden Supercomputersimulationen durchgeführt, um diese Effekte zu analysieren. Es wird gezeigt, dass die Quanteninterferenz für alle 2S-nnP-Übergänge in Deuterium stark unterdrückt wird, wodurch Präzisionsmessungen dieser Übergänge möglich werden. Darüber hinaus wird ein weiterer Effekt in Deuterium im Vergleich zu Wasserstoff untersucht, der sich aus der Lichtkraft ergibt, die auf die Atome in der stehenden Welle des Spektroskopielichts wirkt. Trotz zusätzlicher Zustandsvielfalt durch die gleichzeitige Anregung unaufgelöster Hyperfeinkomponenten wird gezeigt, dass diese sogenannte ``Lichtkraftverschiebung'' mit dem gut verstandenen Effekt im Wasserstoff vergleichbar ist. Die größte Herausforderung bei der Messung des 2S-6P-Ein-Photonen-Übergangs in Deuterium ist die Doppler-Verschiebung erster Ordnung. Ein großer Teil dieser Arbeit befasst sich daher mit dem verbesserten aktiven faserbasierten Retroreflektor (AFR), der eine Technik zur Unterdrückung dieser Verschiebung darstellt. Der zentrale Teil des AFR ist der Faserkollimator, der für die Erzeugung hochwertiger gegenläufiger Laserstrahlen erforderlich ist. Die Entwicklung und Charakterisierung eines solchen Kollimators für die nahe ultraviolette Wellenlänge des 2S-6P-Übergangs ist eine der wichtigsten Errungenschaften des verbesserten AFR. Die Ergebnisse dieser Arbeit können für andere Anwendungen von Interesse sein, bei denen eine hohe Strahlqualität oder wellenfront-zurückverfolgende Strahlen wichtig sind. Darüber hinaus werden die Einschränkungen der AFR untersucht, die sich aus polarisationserhaltenden Singlemode-Fasern ergeben. Neben anderen Verbesserungen wurde eine Polarisationsüberwachung der Spektroskopielaserstrahlen implementiert. Es werden verschiedene Charakterisierungsmessungen vorgestellt, um die Leistungsfähigkeit des verbesserten AFR zu demonstrieren. Schließlich wird in dieser Arbeit eine vorläufige Messung des 2S-6P-Übergangs in Deuterium vorgestellt. Für diese Messung wurde ein neuer Kryostat in die Apparatur eingebaut, der die Stabilität des Spektroskopiesignals durch reduzierte Temperaturschwankungen verbessert. Die Erzeugung des kryogenen Deuterium-Atomstrahls wurde in Abhängigkeit von der Düsentemperatur analysiert, was eine wichtige Studie für künftige Spektroskopiemessungen darstellt. Darüber hinaus wurden für die Präzisionsmessung verschiedene systematische Effekte untersucht, darunter die Fehlausrichtung des Atomstrahls und die elektrischen Streufelder. Es wird gezeigt, dass eine Präzisionsmessung des 2S-6P-Übergangs in Deuterium mit einer ähnlichen Unsicherheit wie in Wasserstoff machbar ist. Nach der vorläufigen Unsicherheitsabschätzung kann die 2S1/2_{1/2}-6P1/2_{1/2}-Übergangsfrequenz in Deuterium auf \SI{1.7}{kHz} bestimmt werden, was einer relativen Genauigkeit von 2.3×10122.3 \times 10^{-12} entspricht. Zusammen mit der 1S-2S-Messung kann dieses Ergebnis bereits die genauesten Bestimmungen des Deuteronenradius und der Rydberg-Konstante aus dem elektronischen Deuterium ermöglichen, sodass die Unsicherheiten für die Rydberg-Konstante und den Deuteronenradius δR5×105m1\delta R_\infty \simeq 5\times 10^{-5}\,\text{m}^{-1} bzw.~\delta r_d \simeq \SI{0.002}{fm} betragen. Dieses Ergebnis bildet die Grundlage für eine zukünftige Präzisionsmessung, bei der die 2S-6P-Übergangsfrequenz mit ähnlicher Genauigkeit wie bei Wasserstoff bestimmt werden soll, was δR2×105m1\delta R_\infty \simeq 2\times 10^{-5}\,\text{m}^{-1} und \delta r_d \simeq \SI{0.0007}{fm} entsprechen würde. Der Vergleich mit dem Ergebnis von myonischem Deuterium würde es dann erlauben, die QED-Theorie für gebundene Zustände auf dem Niveau von 9×10139 \times 10^{-13} zu testen.Quantum electrodynamics (QED) forms the basis for all other quantum field theories, upon which the Standard Model of particle physics is constructed. Currently, it is clear that our fundamental understanding of nature is incomplete, such that the Standard Model is expected to be modified or extended by new particles or interactions. One way to explore these frontiers of fundamental physics is to perform precision measurements. This thesis studies the precision laser spectroscopy of deuterium, where the transition energies between different energy states of the electron bound to the nucleus can be accurately measured with techniques such as ultra-stable lasers and the frequency comb. Due to the simplicity of hydrogen-like atoms, their energy levels can be precisely calculated from bound-state QED and confronted with the experiment with the relative accuracy on the order of 101210^{-12}. Such a comparison between theory and experiment is linked to the determination of fundamental constants, which enter the theory as parameters. Only if more indepedendent measurements are available than there are parameters, the theory can be tested. The comparison between theory and laser spectroscopy in deuterium concerns the Rydberg constant RR_\infty and the deuteron charge radius rdr_d. This requires at least two different transition frequency measurements to determine those constants, and more measurements to test the theory. Contrary to hydrogen, only few accurate enough transition frequency measurements are available in deuterium. This thesis presents the first study of the 2S-6P transition in deuterium, which can be combined with the existing 1S-2S transition frequency measurement to obtain RR_\infty and rdr_d. Together with the 2S-2P transition measurement from muonic deuterium, this determination provides a theory test. Such a comparison is important to shine light on the persisting discrepancy between the result from muonic deuterium and the average of previous data from electronic deuterium, as well as tensions between the recent results from hydrogen spectroscopy. In contrast to hydrogen, precision spectroscopy of the 2S-6P transition in deuterium is complicated by the simultaneous excitation of unresolved hyperfine components, possibly leading to unresolved quantum interference. This thesis studies the possible systematic effects associated with this complication. Along with analytical perturbative models, supercomputer simulations are performed to analyze these effects. It is shown, that quantum interference is strongly suppressed for all 2S-nnP transitions in deuterium, making precision measurements of these transitions possible. Furthermore, another effect is studied in deuterium compared to hydrogen, which arises from the light force acting on the atoms in the standing wave of the spectroscopy light. Despite additional state manifolds from the simultaneous excitation of unresolved hyperfine components, it is shown that this so-called ``light force shift'' is comparable to the well understood effect in hydrogen. The main challenge of measuring the one-photon 2S-6P transition in deuterium is the first-order Doppler shift. Therefore, a large part of this thesis contributes to the improved active fiber-based retroreflector (AFR), which is a technique to suppress this shift. The central part of the AFR is the fiber collimator, which is required to produce high-quality counter-propagating laser beams. Designing and characterizing such a collimator for the near ultra-violet wavelength of the 2S-6P transition is one of the main achievements of the improved AFR. The results of this work can be of interest to other applications where a high beam quality or wavefront-retracing beams are important. Furthermore, the limitations of the AFR arising from single-mode polarization-maintaining fibers are investigated. Along with other improvements, a polarization monitor of the spectroscopy laser beams has been implemented. Various characterization measurements are presented to demonstrate the performance of the improved AFR. Finally, this thesis presents a preliminary measurement of the 2S-6P transition in deuterium. For this measurement, a new cryostat has been installed in the apparatus, which improves the stability of the spectroscopy signal due to reduced temperature fluctuations. The cryogenic deuterium atomic beam generation has been analyzed in dependence on the nozzle temperature, which is an important study for future spectroscopy measurements. Furthermore, for the precision measurement different systematic effects have been investigated, including the atomic beam misalignment and the stray electric fields. It is demonstrated that a precision measurement of the 2S-6P transition in deuterium with a similar uncertainty than in hydrogen is feasible. According to the preliminary uncertainty budget, the 2S1/2_{1/2}-6P1/2_{1/2} transition frequency in deuterium can be determined to \SI{1.7}{kHz}, which corresponds to 2.3×10122.3 \times 10^{-12} relative accuracy. Together with the 1S-2S measurement, already this result can enable the most accurate determinations of the deuteron radius and the Rydberg constant from the electronic deuterium with the uncertainties on the Rydberg constant and the deuteron radius of δR5×105m1\delta R_\infty \simeq 5\times 10^{-5}\,\text{m}^{-1} and \delta r_d \simeq \SI{0.002}{fm}, respectively. This result sets the stage for a future precision measurement, where the 2S-6P transition frequency is expected to be determined with the similar accuracy as in hydrogen, which would correspond to δR2×105m1\delta R_\infty \simeq 2\times 10^{-5}\,\text{m}^{-1} and \delta r_d \simeq \SI{0.0007}{fm}. The comparison to the result from muonic deuterium would then allow to test bound-state QED at the level of 9×10139 \times 10^{-13}

    Practitioner perspectives of technology use in early years settings.

    Get PDF
    Perspectives of early years practitioners in English preschools were the focus for this thesis. Particularly exploring the use technology in the EYP role, and how they support children to use technology. Originally, intending to explore how the removal of technology and ICT from the 2021 revised Early Years Foundation Stage (EYFS) framework would affect provision, data was collected during the national lockdowns of COVID-19, so practitioners also shared experiences of how the use of technology and digital media changed during this time, and how children’s technology and digital media use in settings differed from pre lockdown. To ensure data collection could continue during lockdowns, the original data collection method of focus groups changed to telephone interviews and online questionnaires that allowed 103 practitioners to share their views. However, despite a change in methods, a qualitative methodology remained. Data suggests practitioners used digital media more during periods of lockdown, providing learning opportunities for children, meeting virtually with colleagues, and supporting parents. Children’s technology and digital media use in settings also changed; due to policy guidance, sanitising equipment and keeping children in ‘bubbles’ meant sharing devices became more difficult. Practitioners shared opinions and beliefs that children use technology too much at home, without considering whether children use technology for consumption or creation in these spaces. Further, practitioners often use technology with children to ‘tick a box’ for OFSTED without considering how these technologies can be woven into the classroom ecology to benefit all areas of learning and development as a tool for multimodal learning. Recommendations for practice include working with qualification awarding organisations to ensure early years qualifications include some content on technology use, and the creation of a lead practitioner role (Digital Activity Lead Co-ordinator, or DALCo) who can champion and lead technology use in their setting
    corecore