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Impact of Anterior Malposition and Bone Cement Augmentation on the Fixation Strength of Cephalic Intramedullary Nail Head Elements
No full textBackground and Objectives: Intramedullary nailing of trochanteric fractures can be challenging
and sometimes the clinical situation does not allow perfect implant positioning. The aim of this
study was (1) to compare in human cadaveric femoral heads the biomechanical competence of two
recently launched cephalic implants inserted in either an ideal (centre–centre) or less-ideal anterior
off-centre position, and (2) to investigate the effect of bone cement augmentation on their fixation
strength in the less-ideal position. Materials and Methods: Fourty-two paired human cadaveric femoral
heads were assigned for pairwise implantation using either a TFNA helical blade or a TFNA screw as
head element, implanted in either centre–centre or 7 mm anterior off-centre position. Next, seven
paired specimens implanted in the off-centre position were augmented with bone cement. As a result,
six study groups were created as follows: group 1 with a centre–centre positioned helical blade,
paired with group 2 featuring a centre–centre screw, group 3 with an off-centre positioned helical
blade, paired with group 4 featuring an off-centre screw, and group 5 with an off-centre positioned
augmented helical blade, paired with group 6 featuring an off-centre augmented screw. All specimens
were tested until failure under progressively increasing cyclic loading. Results: Stiffness was not
significantly different among the study groups (p = 0.388). Varus deformation was significantly
higher in group 4 versus group 6 (p = 0.026). Femoral head rotation was significantly higher in
group 4 versus group 3 (p = 0.034), significantly lower in group 2 versus group 4 (p = 0.005), and
significantly higher in group 4 versus group 6 (p = 0.007). Cycles to clinically relevant failure were
14,919 4763 in group 1, 10,824 5396 in group 2, 10,900 3285 in group 3, 1382 2701 in group
4, 25,811 19,107 in group 5 and 17,817 11,924 in group 6. Significantly higher number of cycles
to failure were indicated for group 1 versus group 2 (p = 0.021), group 3 versus group 4 (p = 0.007),
and in group 6 versus group 4 (p = 0.010). Conclusions: From a biomechanical perspective, proper
centre–centre implant positioning in the femoral head is of utmost importance. In cases when this
is not achievable in a clinical setting, a helical blade is more forgiving in the less ideal (anterior)
malposition when compared to a screw, the latter revealing unacceptable low resistance to femoral
head rotation and early failure. Cement augmentation of both off-centre implanted helical blade and
screw head elements increases their resistance against failure; however, this effect might be redundant for helical blades and is highly unpredictable for screws
Improving Early Optics Instruction Using a Phenomenological Approach: A Field Study
No full textPrevious research has shown that phenomenological approaches in early optics education
might be superior to traditional model-based instruction based on the light ray realm with regards
to fostering students’ conceptual understanding of basic optics topics. However, it remains open
to date which learning difficulties students encounter when being introduced to optics following
a phenomenological approach—in particular, in comparison to the learning difficulties that are
widespread among students introduced to optics via traditional model-based instruction. With
this article, we contribute to closing this gap: We report the results of a quasi-experimental field
study with N = 189 secondary school students. We used ten items adapted from the literature in
a pre-posttest design for an in-depth exploration of the conceptions of introductory optics topics
acquired by N = 89 students introduced to optics following a phenomenological teaching-learning
sequence and compare these students’ conceptions to the ones acquired by N = 100 peers who
participated in traditional model-based instruction covering the same content topics. The results of
this study substantiate earlier findings according to which phenomenological teaching might be a
fruitful endeavour for early optics education, in particular, when it comes to teaching and learning
about image formation by converging lenses
Co-designing Participation with Young People in the Smart City: Learning from the Early Stages of a Co-design Process with an Overlooked Group
No full textDESIGNING GOVERNANCE – POWER AND COMPLICITY:1 Introduction
2 Theoretical Framework
2.1 Design Framework
2.2 Smart city planning with youth
3 Case study: early stages of a co-creation process for participation formats with teenagers in Potsdam, Germany
3.1 Stakeholder overview
3.2 Workshops
4 Learnings from the case Study
4.1 Frontstage Environment: Lived realities and participatory prototyping
4.2 Backstage environment: weaving fabric over solid structure
4.3 Design challanges
5 Conclusion
Acknowledgement
ReferencesIn urban planning, and more recently in the planning of socalled smart cities in Germany, the active involvement of residents has become established practice. One group that has been overlooked in this regard is young people. This paper draws on a case study from the early stages of a co-creation process within the Smart City Potsdam
model project, in which participation formats were co-designed with 12th grade students, to describe a new design space for youth participation. The theoretical framework of the case study is based on practice-based research, participatory and design for policy. The network of stakeholders, the four co-design workshops conducted, the learnings and challenges are described in detail. It is suggested that the translative potential and the connective approach of participatory design and co-design may be suitable to meet the challenges of involving the heterogeneous group of young people, especially teenagers, in the urban planning process. Based on the findings of the case study, the paper argues that there is a gap in research in this area and an opportunity for designers to support youth participation in urban planning.:1 Introduction
2 Theoretical Framework
2.1 Design Framework
2.2 Smart city planning with youth
3 Case study: early stages of a co-creation process for participation formats with teenagers in Potsdam, Germany
3.1 Stakeholder overview
3.2 Workshops
4 Learnings from the case Study
4.1 Frontstage Environment: Lived realities and participatory prototyping
4.2 Backstage environment: weaving fabric over solid structure
4.3 Design challanges
5 Conclusion
Acknowledgement
Reference
«Wer sind wir, wenn wir gestalten?»: Zur Ko-Konstitution von Rollenbildern im Design
No full textDESIGNING GOVERNANCE – POWER AND COMPLICITY:1 Einleitung
1.1 Forschungsfragen
1.2 Vorgehen
2 Stereotypen, Kreativität und das Entwerfen
3 Im Auftrag: Das Briefing
4 Selbstinitiiert oder im Auftrag Dritter?
5 Kuratieren und Kollaborieren
6 Werte aushandeln: creative Entrepreneurs
7 Fazít
ReferencesDefinitionen des Designs basieren meist auf mehr oder weniger expliziten Vorstellungen des Entwerfens und der Kreativität. Für die Selbst- und Fremdwahrnehmung von Designer:innen ist beides konstitutiv, ebenso die ökonomische Verankerung der Designpraxis. Anhand von Aufträgen aus dem kulturellen Sektor und der Neuausrichtung
der Designförderung auf Bundesebene, untersucht der Beitrag die Konstitution von Auto- und Heterostereotypen im Schweizer Design um die Jahrtausendwende. Der Fokus der Analyse liegt auf den als diskursive Praktiken definierten Portfolio und Briefing. Befragt wird, wie die Akteur:innen in Aushandlungsprozessen kokonstituieren, wer sie sind, wenn sie ‹gestalten›. Die Analyse basiert methodisch auf der Auto- und Heterostereotypenforschung. Obgleich im Designprozess unterschiedlich positioniert, sind Portfolio
und Briefing in ihrer jeweiligen Funktion Bestandteil der Ökonomisierung des Entwerfens als Teil einer umfassenden Ökonomisierung der Gesellschaft. Unterfütterten seit den 1990er Jahren die Begriffe Autorschaft und Kreativität kulturell geframte Auto- und Heterostereotypen im Design, so sahen sich Designer:innen in den Nullerjahren mit Rollenerwartungen des Creative Entrepreneurs konfrontiert. Zusammen mit dem Stereotyp des Kuratierens entstanden so zwei neue Rollenbilder. Als gemeinsames Ziel definieren die in der Ko-Konstitution verbundenen Akteur:innen Distinktion mittels kreativer Neuheit.:1 Einleitung
1.1 Forschungsfragen
1.2 Vorgehen
2 Stereotypen, Kreativität und das Entwerfen
3 Im Auftrag: Das Briefing
4 Selbstinitiiert oder im Auftrag Dritter?
5 Kuratieren und Kollaborieren
6 Werte aushandeln: creative Entrepreneurs
7 Fazít
Reference
Noten für die 'Neue Welt': Anfänge des Nordamerikahandels im Verlag C. F. Peters
No full textZiel der Masterarbeit ist es, möglichst viele Kunden und Geschäftspartner des Leipziger Musikverlags C. F. Peters in Nordamerika für den Zeitraum von etwa 1818 (frühester Nachweis) bis 1853 (Tod des Verlagsleiters C. G. S. Böhme) zu identifizieren und Art, Dauer und Entwicklung der Geschäftsbeziehungen zu beleuchten.The aim of the master's thesis is to identify as many customers and business partners of the Leipzig music publisher C. F. Peters in North America as possible for the period from around 1818 (earliest evidence) to 1853 (death of the director C. G. S. Böhme) and to shed light on the nature, duration and development of the business relationships
Tailoring Phonon Polaritons in 2D van-der-Waals Materials
No full textTailoring and precisely controlling the propagation of confined light precisely at the nanometer-length scale is an ubiquitous requirement for the realization of integrated optics and, hence, a major goal of the current research in nano-optics. Phonon polaritons (PhPs) - quasi-particles formed by the interaction of light with excitations of the crystal lattice - propagating in thin layers of van-der-Waals (vdW) materials are key to solve this challenge, as they intrinsically offer high confinement of light coupled with low losses, as well as an inherent directional energy transport profiting from the lattice anisotropy of the polariton-hosting material. Furthermore, their strong interaction with surrounding media due to their high surface-to-volume ratio allows for tuning of their wavelengths, shape of wavefront and type of propagation, e.g. via changing the substrate permittivity or stacking multiple layers of polariton-hosting vdW materials under defined twist angles (twistoptics). However, due to the limited access to light sources and detectors operating at frequencies in the so-called THz gap between 0.1 and 10 THz, the research so far had focused to the mid-infrared (MIR) frequency range, omitting the reststrahlen bands of numerous materials spectrally located at or in the THz range.
The present work focuses precisely on such PhPs spectrally located at THz frequencies and the tailoring of their propagation behavior. For that purpose, the vdW materials α-molybdenum trioxide (α-MoO3) and α-germanium monosulfide (α-GeS), featuring THz reststrahlen bands between 7.85 to 11.8 THz and 6.06 to 9.70 THz, respectively, have been employed as polariton-hosting materials. Specifically, within the framework of this thesis, the manipulation of the PhP propagation of THz PhPs is achieved via two approaches: First, the deposition of the two polariton-hosting materials onto different substrate materials, including three isotropic materials (Si, SiO2, and Ge) featuring different dielectric responses, and the highly anisotropic β-gallium oxide (bGO) under different twist angles. By doing so the tuning of the PhP wavelengths and the directionality of their propagation as well as the observation of unidirectional ray-like PhPs is achieved. Second, the stacking of two flakes of the polariton-hosting materials to homo- and heterostacks. This extension of the concept of twistoptics from the MIR frequency range to the THz regime enables the tuning of the THz PhP propagation between in-plane hyperbolic and in-plane elliptic, including the first observation of canalized THz PhPs.
All studies presented in this work are conducted by combining theoretical simulations, including analytical transfer-matrix calculations and numerical full-wave approaches, with experimental measurements, performed with scattering-type scanning near-field optical microscopy (s-SNOM) utilizing the free-electron laser FELBE (Dresden, Germany) as the tunable THz light source. This unique combination allows for the measurement of the optical properties of materials at frequencies between 1.2 and 60 THz, covering a large part of the THz gap, with a lateral resolution down to 20 nm, thus enabling the real-space visualization of the target PhP propagations at the 2D surfaces.
Overall, these studies explore different methods to tune the propagation of THz PhPs, extending the frequency range of tailoring polaritons and thus contributing to the development in the booming field of THz nano-optics.:1 Introduction 1
2 Fundamentals 5
2.1 Phonon Polaritons 5
2.1.1 Phonons and their Interaction with Light 6
2.1.2 Types of Phonon Polaritons 7
2.1.3 Theoretical Models Describing Phonon Polaritons 13
2.2 Van-der-Waals (vdW) Materials 18
2.2.1 Properties of vdW Materials 19
2.2.2 Twistoptics 20
2.3 Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) 22
2.3.1 Historic Development of SNOM 23
2.3.2 Scanning Force Microscopy (SFM) 24
2.3.3 Decoupling Near- and Far-Field in s-SNOM 27
2.3.4 Examples of s-SNOM applications 31
3 Setup and Materials 33
3.1 Experimental Setup 33
3.1.1 s-SNOM instrument neaSNOM 34
3.1.2 Free-Electron Laser FELBE 39
3.1.3 Light Detection 42
3.1.4 Utilized Setup Parameters 44
3.2 Data Acquisition 44
3.2.1 Data Processing 45
3.2.2 Extraction of Polariton Parameters 50
3.2.3 2D Fast Fourier Transformation with 'Zero Padding' 52
3.3 Materials 53
3.3.1 α-Molybdenum Trioxide (α-MoO3) 53
3.3.2 α-Germanium Monosulfide (α-GeS) 57
3.3.3 β-Gallium Oxide (β-Ga2O3) 61
3.3.4 Isotropic Substrates 64
3.4 Sample Preparation 65
3.4.1 Exfoliating Layers of vdW Materials 65
3.4.2 Pre-Characterization 67
3.4.3 Sample Structuring for the PhP Propagation-Shape Imaging 70
4 Results I: Tuning Phonon Polaritons in vdW Single Layers via Substrates 75
4.1 General Theoretical Considerations 76
4.1.1 Tuning via an Isotropic Substrate 76
4.1.2 Tuning via an Anisotropic Substrate 79
4.2 Tuning Hyperbolic Phonon Polaritons in Single-Layers
of α-Molybdenum Trioxide 82
4.2.1 Impact of the Substrate Permittivity vs. Layer Thickness 82
4.2.2 Enhanced Tuning via Substrate Anisotropy: Utilizing β-Gallium Oxide as Substrate 86
4.3 Tuning Phonon Polaritons in Single-Layers of α-Germanium Monosulfide 94
4.3.1 The Complex Dispersion of α-Germanium Monosulfide 95
4.3.2 Tuning the Dispersion Splitting via the Substrate Permittivity 99
4.3.3 Impact of the Substrate Permittivity on the In-Plane Propagation Shape 104
4.3.4 Analyzing the Origin of the Dispersion Splitting 109
4.4 Chapter Conclusion 115
5 Results II: Tuning Phonon Polaritons in Twisted Bi-Layer Stacks 117
5.1 Twisted Bilayer α-Molybdenum Trioxide at THz frequencies 117
5.1.1 Theoretical Considerations 118
5.1.2 Experimental Observations 120
5.1.3 Quantitative Characterization of the Measured THz Phonon Polaritons 126
5.1.4 Canalization of Hyperbolic Phonon Polaritons 129
5.2 Heterostacks made up from α-Germanium Monosulfide on α-Molybdenum Trioxide 130
5.2.1 Preliminary Experimental Observations 131
5.2.2 Theoretical Predictions 134
5.3 Chapter Conclusion 138
6 Final Conclusion 141
Appendices 145
A1 Comprehensive Overview of the s-SNOM Performance for Different Experimental Settings 147
A1.1 Extracted Signal-to-Noise Ratios 148
A1.2 Images of the Performed Retracts 156
A1.3 Images of the Performed Scans 162
A2 Additional Measurements of Twisted α-MoO3 Homostacks 163
Bibliography 165
Own Publications 17
Potential- und Gefährdungsbeurteilung zur Erfassung und Beurteilung von Wohlbefinden und psychischen Gefährdungen unter dreijähriger Kinder in Kindertageseinrichtungen - Handreichung
No full textPrivacy-Preserving Analytics of Human Mobility Data: Investigating the Gap between State-Of-The-Art Privacy Methods and Real-Life Utility Requirements
No full textIn recent years, human mobility data has been increasingly collected and stored, mainly due to the ubiquitous use of smartphones, producing a constant stream of cellular network and GPS data. This provides an unprecedented resource for useful applications in various fields, such as urban and traffic planning or disaster response. At the same time, as more and more data becomes available, individuals' privacy is increasingly at risk. As a result, there is a growing body of research on privacy-enhancing technologies. Such methods, however, come with an inherent utility-privacy trade-off, where the usefulness of the data is traded for privacy. State-of-the-art techniques like methods ensuring differential privacy are not (yet) applied to a large extent in practical settings. This thesis examines privacy-preserving technologies for human mobility data in terms of their usefulness for modeling and analysis projects, with a particular focus on real-world practices. A differentially private mobility data report is proposed to serve practitioners as a tool to provide typical mobility data statistics with high privacy standards. Synthetic data generation methods are explored in-depth and can thus far not be recommended for usage in practice. For this purpose, existing methods for evaluating the utility of synthetic or otherwise privacy-enhanced mobility data are critically reviewed with regard to their suitability for various application scenarios and supplemented by more practice-relevant measures. Analytics of mobility data in a privacy-preserving manner remains an ongoing issue requiring context-specific solutions.:Introduction
1.1 Motivation
1.2 Scope
1.3 Contribution and Thesis Outline
2 Background and Related Work
2.1 Human Mobility Data
2.1.1 Spatio-Temporal Trajectories
2.1.2 Data Sources
2.1.3 Applications
2.1.4 Utility Measurement
2.2 Technical Anonymization
2.2.1 Basic Privacy Mechanisms
2.2.2 k-Anonymity
2.2.3 Di!erential Privacy
2.2.4 Synthetic Data
2.2.5 Legal Perspective
3 Collection, Usage and Privacy of Mobility Data in the Enterprise and Public Administrations
3.1 Introduction
3.2 Publication
3.3 Conclusion
4 Towards Mobility Reports with User-Level Privacy
4.1 Introduction
4.2 Publication
4.3 Conclusion
5 Generative Models for Synthetic Urban Mobility Data: A Systematic Literature Review
5.1 Introduction
5.2 Publication
5.3 Conclusion
6 Reconsidering Utility: Unveiling the Limitations of Synthetic Mobility Data Generation Algorithms in Real-Life Scenarios
6.1 Introduction
6.2 Publication
6.3 Conclusion
7 Conclusion and Discussion 7.1 Mobility Data Analytics Applications in Need of Technical Anonymization
7.2 Utility Measures
7.3 Differential Privacy and Mobility Data
7.4 Synthetic Mobility Data
7.5 Beyond Technical Anonymization
Reference
Studying Users’ Perceptions of COVID-19 Mobile Applications in Saudi Arabia
No full textIn Saudi Arabia, several mitigating measures were implemented in response to the COVID-19 pandemic, including the creation of COVID-19 mobile applications (apps) for public use. The Saudi government has made the use of these apps mandatory for its citizens and residents. However, it is essential to explore the perception that common users have regarding using these apps in terms of usability and user experience. Therefore, this paper assesses user experience in terms of effectiveness, efficiency, and user satisfaction with the usability of the Saudi COVID-19 apps. The reviews of five mobile apps launched by the Saudi Data and AI Authority (SDAIA) and the Ministry of Health in the Apple Store were extracted using an online tool and analyzed using the content analysis method. The number of collected reviews was 29 for Sehha, 406 for Sehhaty, 442 for Mawid, 107 for Tabaud, and 1338 for Tawakkalna. The results of the study showed that Mawid (82%) and Tabaud (81%) had the highest usability of all the apps studied. Sehha (−138%) and Sehhaty (−107%) received the lowest usability scores, followed by Tawakkalna (−22%). Based on these results, we identified several usability issues with each app. Some of the main problems reported by users were increased battery drain, lack of privacy, and technical issues
Use of Envelope Domain III Protein for the Detection of IgG Type Antibodies Specific to Zika Virus by Indirect ELISA
No full textZika virus (ZIKV) diagnostics are crucial for proper antenatal and postnatal care and also for surveillance and serosurvey studies. Since the viremia during ZIKV infection is fleeting, serological testing is highly valuable to inform diagnosis. However, current serology tests using whole virus antigens frequently suffer from cross reactivity issues, delays, and technical complexity, especially in low and middle income countries (LMICs) and endemic countries. Here, we describe an indirect ELISA to detect specific IgG antibodies using the ZIKV envelope domain III (EDIII) protein expressed in Drosophila S2 cells as an immunogen. Using a total of 367 clinical samples, we showed that the EDIII-ELISA was able to detect IgG antibodies against ZIKV with high sensitivity of 100.0% and specificity of 94.7% when compared to plaque reduction neutralization tests (PRNTs) as the gold standard and using 0.208 as the cut-off OD value. These results show the usefulness of the recombinant envelope domain III as an alternative to standard whole virus proteins for ZIKV diagnostics as it improves the sensitivity and specificity of IgG ELISA assay when used as an immunogen. This method should, therefore, be extended to serological diagnostic techniques for other members of the flavivirus genus and for use in IgM diagnostic testing