Electronic states in semiconductor nanostructures and upscaling to semi-classical models

In semiconductor devices one basically distinguishes three spatial scales: The atomistic scale of the bulk semiconductor materials (sub-Angstroem), the scale of the interaction zone at the interface between two semiconductor materials together with the scale of the resulting size quantization (nanometer) and the scale of the device itself (micrometer). The paper focuses on the two scale transitions inherent in the hierarchy of scales in the device. We start with the description of the band structure of the bulk material by kp Hamiltonians on the atomistic scale. We describe how the envelope function approximation allows to construct kp Schroedinger operators describing the electronic states at the nanoscale which are closely related to the kp Hamiltonians. Special emphasis is placed on the possible existence of spurious modes in the kp Schroedinger model on the nanoscale which are inherited from anomalous band bending on the atomistic scale. We review results of the mathematical analysis of these multi-band kp Schroedinger operators. Besides of the confirmation of the main facts about the band structure usually taken for granted, key results are conditions on the coefficients of the kp Schroedinger operator for the nanostructure, which exclude spurious modes and an estimate of the size of the band gap. Using these results, we give an overview of properties of the electronic band structure of strained quantum wells. Further, the assumption of flat-band conditions across the nanostructure allows for upscaling of quantum calculations to state equations for semi-classical models. We demonstrate this approach for parameters such as the quantum corrected band-edges, the effective density of states, the optical response, and the optical peak gain. Further, we apply the kp Schroedinger theory to low gap quantum wells, a case where a proper rescaling of the optical matrix element is necessary to avoid spurious modes. Finally, we discuss the application of the kp Schroedinger models to biased quantum wells, the operation mode of electro-optic modulators

Dimensionalisierung, Gruppenbildung und Wahrscheinlichkeitsübergang: zur Identifizier- und Interpretierbarkeit multivariater Beziehungen zwischen Milieu, Beruf und Weiterbildung an SOEP-Daten

'Der Artikel behandelt Fragen der Milieu- und Bildungsbeteiligungsforschung primär unter methodischen Gesichtspunkten der Auswertung aus verschiedenen Erhebungen des SOEP (Erhebungen 1994 und 1999). Im Zentrum steht die Frage, in welcher Weise Milieuzugehörigkeit und Weiterbildungsbeteiligung aufeinander bezogen werden können. Die Rekonstruktion des Zusammenhangs erfolgt auf der Grundlage multivariater Verfahren der Objekt- und Variablenklassifikation. Gezeigt wird, dass mittels einer gezielten, auf die Analyse von Milieus zugeschnittenen Kombination solcher Verfahren die Unterscheidung milieuspezifischer von milieuunspezifischen Bestimmungsfaktoren der Weiterbildungsbeteiligung gelingen kann. Auf diese Weise ist es möglich, eine inhaltliche und methodische Schwäche der bildungsbezogenen Milieuforschung sichtbar zu machen: Nicht nur die innere Unterscheidbarkeit von Milieus, sondern auch die Unterscheidung von Milieu und Nicht- Milieu ist eine für die Einschätzung von Milieus als unabhängige Variable inhaltlich und methodisch erforderliche Operation.' (Autorenreferat)'The article deals with issues from milieu research and research on participation in education, primarily looking at methodological aspects in the analysis of various surveys from the SOEP (surveys 1994 and 1999). The central question is how milieu and participation in further education are related to each another. The relationship is reconstructed on the basis of multivariate procedures for classifying objects and variables. It will be shown that milieu-specific factors for participation in further education can be distinguished from milieu-non-specific factors, namely by systematically combining these multivariate procedures in such a way that the combination is tailored to the analysis of milieus. Thus a weakness regarding content and methodology can be made visible in milieu research focusing on education: in order to assess milieus as an independent variable, both matter and methodology require not only a differentiation between various types of milieus, but also between milieu and non-milieu.' (author's abstract)

Der schiefe Turm von PISA: die logistischen Parameter des Rasch-Modells sollten revidiert werden

'Die Kompetenz- und Anforderungsmessungen in den PISA-Studien beruhen auf dem logistischen Rasch-Modell, welches der probabilistischen Testtheorie zu Grunde liegt. Dieses Modell weist Schwächen auf. Wegen der logistischen item response Funktion lässt es Sätze von Antworten zu, die zwar legitim aber mit den vorgesehenen Parametern nicht auswertbar sind. Es handelt sich um die uniform beantworteten Fragebögen. Mit deren Sonderstellung hängt zusammen, dass die Schätzer für besonders hohe wie auch besonders niedrige Kompetenzen systematisch vom wahren Wert des Parameters abweichen und dass die Fehlerintervalle beliebig groß werden. Dies erschwert die Interpretation der Schätzer sowie die sozialwissenschaftliche Verwendung der Resultate - z.B. in Regressionsanalysen. Es sind aber gerade die oberen und unteren Kompetenzniveaus und Schwierigkeitsstufen, denen das besondere Interesse der Bildungsforschung und Bildungspolitik gilt. Dieses durchaus bekannte Problem wurde bislang formal nicht gelöst. Im vorliegenden Aufsatz wird gezeigt, dass man es lösen kann, indem man zu einer anderen - der trigonometrischen - item response Funktion übergeht.' (Autorenreferat)'The attainment of persons and the difficulties of items are measured via the logistic Rasch model which is the basis of probabilistic test theory. This model has a weakness. Due to the logistic item response function it admits sets of answers that - although they are legitimate - cannot be analyzed in terms of the parameters of the model. The authors refer to persons that uniformly answer all items either correctly or incorrectly. As a consequence, the estimators of especially high and especially low attainment are systematically biased and the error intervals can become indefinitely large. This obscures the interpretation of the estimators, and makes the results difficult to use in the social sciences. However, the special interest of research and politics is focussed on the upper and lower levels of attainment. The problem is known but has remained unsolved so far. The authors show that one can solve it within the binomial framework of the Rasch model by introducing a new - the so-called trigonometrical - item response function.' (author's abstract)

Learning from students\u27 statements?! - Towards a professional feedback culture at schools

Lehrkräfte sind aufgefordert, die Qualität ihres Unterrichts mithilfe von Schülerrückmeldungen zu überprüfen. In diesem Beitrag wird diskutiert, was unter einer "professionellen Feedbackkultur" in Schulen im Hinblick auf die Verwendung des Schülerfeedbacks zur Messung von Unterrichtsqualität zu verstehen ist und auf welche Verwendungsweisen angesichts des empirischen Forschungsstands zur Validität von Schülerratings zur Unterrichtsqualität möglicherweise auch besser zu verzichten wäre. (DIPF/Orig.)Teachers are encouraged to check the quality of their teaching by using student feedback. This paper discusses what a "professional feedback culture" in schools in the context of measuring teaching quality means. The second question is, whether some uses of student feedback are not useful in light of the empirical research literature on validity of student ratings of teaching quality. (DIPF/Orig.

Audience synchronies in live concerts illustrate the embodiment of music experience

A study of 132 audience members of three classical public concerts (all three staged the same chamber music pieces by Ludwig van Beethoven, Brett Dean, and Johannes Brahms) had the goal of analyzing the physiological and motor responses of audiences. It was assumed that the music would induce synchronous physiology and movement in listeners (induction synchrony). In addition to hypothesizing that such synchronies would be present, we expected that they were linked to participants' aesthetic experiences, their affect and personality traits, which were assessed by questionnaires before and after the concerts. Clear evidence was found of physiological synchrony (heart rate, respiration rate, skin conductance response) as well as movement synchrony of the audiences, whereas breathing behavior was not synchronized. Thus the audiences of the three concerts resonated with the music, their music perception was embodied. There were links between the bodily synchrony and aesthetic experiences: synchrony, especially heart-rate synchrony, was higher when listeners felt moved emotionally and inspired by a piece, and were immersed in the music. Personality traits were also associated with the individual contributions to induction synchrony

Genomic analysis of single cytokeratin-positive cells from bone marrow reveals early mutational events in breast cancer

SummaryChromosomal instability in human breast cancer is known to take place before mammary neoplasias display morphological signs of invasion. We describe here the unexpected finding of a tumor cell population with normal karyotypes isolated from bone marrow of breast cancer patients. By analyzing the same single cells for chromosomal aberrations, subchromosomal allelic losses, and gene amplifications, we confirmed their malignant origin and delineated the sequence of genomic events during breast cancer progression. On this trajectory of genomic progression, we identified a subpopulation of patients with very early HER2 amplification. Because early changes have the highest probability of being shared by genetically unstable tumor cells, the genetic characterization of disseminated tumor cells provides a novel rationale for selecting patients for targeted therapies

Histopathological and patient-related characteristics of basal cell carcinomas of the head and neck influencing therapeutic management

The authors hypothesize that histopathological characteristics of basal cell carcinomas of the head and neck (BCCHN) have changed over time and the correlation of BCCHN localization and histological tumour type can help improving the number and quality of necessary therapeutic interventions. Information of 222 patients with 344 BCCHN was gained. Descriptive measures were compared to prior studies to prove whether or not characteristics of basal cell carcinomas or patients have changed over time. Afterwards descriptive measures were correlated with number of conducted operations to evaluate if tumour localization, histological tumour type and number of operations depend on one another. Aggravating factors which lead to a higher number of operations were older age, greater size of BCCHN, adjacent elastosis, the localizations eye, ear and nose and histological tumour types morpheaform and nodularulcerated. In comparison to earlier studies characteristics of BCCHN and patients showed positive developments because of grown awareness of BCCHN. Furthermore, our correlations demonstrate that therapeutic results of BCCHN treatment are continuously improving. Nevertheless, treatment of aggressive morpheaform BCCHN in combination with distinctive patient characteristics still needs improvement

Helmholtz Open Science Workshop „Zugang zu und Nachnutzung von wissenschaftlicher Software“ #hgfos16, Report; November 2016

Der Report des Helmholtz Open Science Workshops „Zugang zu und Nachnutzung von wissenschaftlicher Software“ #hgfos16 behandelt die Themen Standards und Qualitätssicherung; Reproduzierbarkeit; Lizenzierung und weitere rechtliche Aspekte; Zitation und Anerkennung; Sichtbarkeit und Modularität; Geschäftsmodelle; Personal, Ausbildung, Karrierewege. Diese Themen sind eng miteinander verzahnt. Für jeden Themenbereich werden jeweils die Relevanz, Fragestellungen, Herausforderungen, mögliche Lösungsansätze und Handlungsempfehlungen betrachtet

Совершенствование товарной политики предприятия

Важным инструментом маркетинговой деятельности предприятия является товарная политика. Умелое управление товарной политикой позволит предприятию выжить в условиях жесткой конкуренции и стать преуспевающим. Объектом исследования является ООО "Хризолит". Цель работы – анализ товарной политики предприятия, товарного ассортимента, а так же конкурентоспособности продукции. В процессе исследования были рассмотрены вопросы: структура номенклатуры и товарного ассортимента, сегментирование рынка и анализ системы продвижения товаров. Изменение экономических показателей предприятия, анализ конкурентов. Областью применения является управление товарной политикой предприятия. Экономическая эффективность заключается в прогнозировании увеличения выручки предприятия и расширении ассортимента.An important tool of marketing activity of enterprise is trade policy. Skillful management of product policy will allow the company to survive in tough competition and become successful. The object of the research is of "Chrysolite". The work purpose – the analysis of the commodity policy of the enterprise, product range and product competitiveness. In the research process was discussed: structure, nomenclature and product portfolio, market segmentation and analysis promotion of products. Change of economic indicators of enterprises analysis of competitors. Scope is the management of a commodity policy of the enterprise. Economic efficiency is forecasting increasing sales and expanding the range