High-Throughput Air-to-Ground Connectivity for Aircraft

Permanent connectivity to the Internet has become the defacto standard in the second decade of the 21st century. However, on-board aircraft connectivity is still limited. While the number of airlines offering in-flight connectivity increases, the current performance is insufficient to satisfy several hundreds of passengers simultaneously. There are several options to connect aircraft to the ground, i.e. direct air-to-ground, satellites and relaying via air-to-air links. However, each single solution is insufficient. The direct air-to-ground coverage is limited to the continent and coastal regions, while the satellite links are limited in the minimum size of the spot beams and air-to-air links need to be combined with a link to the ground. Moreover, even if a direct air-to-ground or satellite link is available, the peak throughput offered on each link is rarely achieved, as the capacity needs to be shared with other aircraft flying in the same coverage area. The main challenge in achieving a high throughput per aircraft lies in the throughput allocation. All aircraft should receive a fair share of the available throughput. More specifically, as an aircraft contains a network itself, a weighted share according to the aircraft size should be provided. To address this problem, an integrated air-to-ground network, which is able to provide a high throughput to aircraft, is proposed here. Therefore, this work introduces a weighted-fair throughput allocation scheme to provide such a desired allocation. While various aspects of aircraft connectivity are studied in literature, this work is the first to address an integrated air-to-ground network to provide high-throughput connectivity to aircraft. This work models the problem of throughput allocation as a mixed integer linear program. Two throughput allocation schemes are proposed, a centralized optimal solution and a distributed heuristic solution. For the optimal solution, two different objectives are introduced, a max-min-based and a threshold-based objective. The optimal solution is utilized as a benchmark for the achievable throughput for small scenarios, while the heuristic solution offers a distributed approach and can process scenarios with a higher number of aircraft. Additionally, an option for weighted-fair throughput allocation is included. Hence, large aircraft obtain a larger share of the throughput than smaller ones. This leads to fair throughput allocation with respect to the size of the aircraft. To analyze the performance of throughput allocation in the air-to-ground network, this work introduces an air-to-ground network model. It models the network realistically, but independent from specific network implementations, such as 5G or WiFi. It is also adaptable to different scenarios. The aircraft network is studied based on captured flight traces. Extensive and representative parameter studies are conducted, including, among others, different link setups, geographic scenarios, aircraft capabilities, link distances and link capacities. The results show that the throughput can be distributed optimally during high-aircraft-density times using the optimal solution and close to optimal using the heuristic solution. The mean throughput during these times in the optimal reference scenario with low Earth orbit satellites is 20 Mbps via direct air-to-ground links and 4 Mbps via satellite links, which corresponds to 10.7% and 1.9% of the maximum link throughput, respectively. Nevertheless, during low-aircraft-density times, which are less challenging, the throughput can reach more than 200 Mbps. Therefore, the challenge is on providing a high throughput during high-aircraft-density times. In the larger central European scenario, using the heuristic scheme, a minimum of 22.9 Mbps, i.e. 3.2% of the maximum capacity, can be provided to all aircraft during high-aircraft-density times. Moreover, the critical parameters to obtain a high throughput are presented. For instance, this work shows that multi-hop air-to-air links are dispensable for aircraft within direct air-to-ground coverage. While the computation time of the optimal solution limits the number of aircraft in the scenario, larger scenarios can be studied using the heuristic scheme. The results using the weighted-fair throughput allocation show that the introduction of weights enables a user-fair throughput allocation instead of an aircraft-fair throughput allocation. As a conclusion, using the air-to-ground model and the two introduced throughput allocation schemes, the achievable weighted-fair throughput per aircraft and the respective link choices can be quantified

Origins of the High Reactivity of Au Nanostructures Deduced from the Structure and Properties of Model Surfaces

In this chapter, experimental and theoretical studies on surface segregation in Ag-Au systems, including our own thermodynamic studies and molecular dynamics simulations of surface restructuring, on the basis of density functional theory are reviewed. The restructuring processes are triggered by adsorbed atomic O, which is supplied and consumed during catalysis. Experimental evidence points to the essential role of Ag impurities in nanoporous gold for activating O2. At the same time, increasing Ag concentration may be detrimental for the selectivity of partial oxidation. Understanding the role of silver requires a knowledge on its chemical state and distribution in the material. Recent studies using electron microscopy and photoelectron spectroscopy shed new light on this issue revealing a non-uniform distribution of residual Ag and co-existence of different chemical forms of Ag. We conclude by presenting an outlook on electromechanical coupling at Ag-Au surfaces, which shows a way to systematically tune the catalytic activity of bimetallic surfaces

Interim-treatment quantitative PET parameters predict progression and death among patients with hodgkin's disease

PURPOSE: We hypothesized that quantitative PET parameters may have predictive value beyond that of traditional clinical factors such as the International Prognostic Score (IPS) among Hodgkin's disease (HD) patients. METHODS: Thirty HD patients treated at presentation or relapse had staging and interim-treatment PET-CT scans. The majority of patients (53%) had stage III-IV disease and 67% had IPS ≥ 2. Interim-treatment scans were performed at a median of 55 days from the staging PET-CT. Chemotherapy regimens used: Stanford V (67%), ABVD (17%), VAMP (10%), or BEACOPP (7%). Hypermetabolic tumor regions were segmented semiautomatically and the metabolic tumor volume (MTV), mean standardized uptake value (SUVmean), maximum SUV (SUVmax) and integrated SUV (iSUV) were recorded. We analyzed whether IPS, absolute value PET parameters or the calculated ratio of interim- to pre-treatment PET parameters were associated with progression free survival (PFS) or overall survival (OS). RESULTS: Median follow-up of the study group was 50 months. Six of the 30 patients progressed clinically. Absolute value PET parameters from pre-treatment scans were not significant. Absolute value SUVmax from interim-treatment scans was associated with OS as determined by univariate analysis (p < 0.01). All four calculated PET parameters (interim/pre-treatment values) were associated with OS: MTV(int/pre )(p < 0.01), SUVmean(int/pre )(p < 0.05), SUVmax(int/pre )(p = 0.01), and iSUV(int/pre )(p < 0.01). Absolute value SUVmax from interim-treatment scans was associated with PFS (p = 0.01). Three calculated PET parameters (int/pre-treatment values) were associated with PFS: MTV(int/pre )(p = 0.01), SUVmax(int/pre )(p = 0.02) and iSUV(int/pre )(p = 0.01). IPS was associated with PFS (p < 0.05) and OS (p < 0.01). CONCLUSIONS: Calculated PET metrics may provide predictive information beyond that of traditional clinical factors and may identify patients at high risk of treatment failure early for treatment intensification

NeSC – NewSpace Communications

Im Rahmen des derzeit stark wachsenden kommerziellen NewSpace-Sektors werden neue Kommunikationssysteme entwickelt – sogenannte „Non-Terrestrial Networks“ (NTN), welche zunehmend auf NewSpace Communications (NeSC)-Systemansätzen basieren. Diese sollen die existierenden terrestrischen Mobilfunk- und leitungsgebundenen Netze zur Sprach-, Video- und Datenkommunikation ergänzen, und damit globale Verfügbarkeit und Omnipräsenz ermöglichen. Die Kombination aus terrestrischen und satellitengestützten Systemen wird die Zuverlässigkeit und räumliche Verfügbarkeit von Kommunikationssystemen insgesamt maßgeblich erhöhen. Als satellitengestützte Kommunikationsplattformen werden hierzu in erster Linie Satelliten-Mega-Constellations (MC) im niedrigen Erdorbit (LEO) entwickelt. Aber auch weiterentwickelte geostationäre Systeme (sog. Very High Throughput Satellites, VHTS) und stratosphärische Träger (High Altitude Platform Systems – HAPS) dienen als Kommunikationsknoten. Eine Vernetzung von Systemen in verschiedenen Orbits bzw. Flughöhen bietet dabei weitere Vorteile, wie z.B. die Kombination von hoher Abdeckung und Sichtbarkeit mit günstigen Linkdistanzen und Frequenzwiederverwendbarkeit. Satellitensysteme können auch mit terrestrischen Kommunikationsnetzen integriert werden. Die Versorgung großer und unterversorgter Gebiete mit Satellitenkommunikation bietet technische und finanzielle Vorteile. Dagegen ist es technisch nicht möglich, die Bevölkerung bzw. Nutzer eines Ballungsgebiets mit Hochgeschwindigkeits-Datendiensten ausschließlich mit LEO-MC basierten Systemen zu versorgen. Die fortschreitende Erweiterung der Nutzung von öffentlichen Kommunikationsnetzen einschließlich NTN-Systemen durch die Digitalisierung von Gesellschaft, Staat und Wirtschaft, von persönlich-kommerziellen auf sicherheitsrelevante Bedarfe für Infrastruktur und Versorgung (wie Energie, Wasser, Bahn, PKW, Gütertransport, Flugverkehr oder behördliche Kommunikation) ist zwingend und uneingeschränkt resilient zu gestalten. Hier bieten weltraumgestützte Netze den großen Vorteil eines weiteren parallelen Kommunikationswegs, um absichtlichen Manipulationen und Störungen auszuweichen. Allerdings ergibt sich in Zusammenhang mit LEO-basierten Satellitennetzen das Risiko, dass es durch die stark zunehmende Anzahl mit Tausenden von kostengünstigen LEO-MC-Satelliten in den knappen Erdumlaufbahnen zu Kollisionen kommt und funktionsuntüchtige Satelliten nicht gezielt aus dem Orbit entfernt werden. Dies kann die institutionelle (Erdbeobachtung, wissenschaftliche Erprobung, Sicherheit) wie auch die astronautische Raumfahrt gefährden. Eine Abhängigkeit Deutschlands und Europas von nicht-europäischen weltraumgestützten und im Wesentlichen kommerziellen Diensten und Systemen sollte bei NeSC vermieden werden, da sie zu den kritischen Infrastrukturen zählen. Die ausschließliche Nutzung und ggf. gar Förderung der technischen und weltraumrechtlichen Entwicklungen aus dem asiatischen und amerikanischen Raum darf für Deutschland und für die EU keine Option sein. Somit benötigt Europa zur Verbesserung der technologischen Souveränität eine eigene weltraum- und stratosphärengestützte Infrastruktur für Anwendungen wie die Ergänzung terrestrischer öffentlicher und privater Kommunikationsinfrastruktur, Anwendungen des globalen Internet-of-Things (IoT), Grenzüberwachung und Sicherung globaler Aufklärungskapazitäten. Die Erfahrungen der ersten Generation von LEO-MCs wie die Wahl ungünstiger Orbits bezüglich der Kollisionsrisiken trotz wirtschaftlicher Vorteile müssen dabei berücksichtigt werden. Mithin kann der zeitverzögerte deutsche und europäische Einstieg in diesem Sinne Vorteile bieten. Wir zeigen in diesem Positionspapier die Eigenschaften und technischen Randbedingungen von NeSC-Systemen auf, beschreiben aktuelle Systemlösungen und Marktteilnehmer, Chancen und Herausforderungen der NeSC-Konzepte und geben abschließend Handlungsempfehlungen für Forschung, Entwicklung und Realisierung von NeSC-Systemen

Measuring Job Crafting Across Cultures: Lessons Learned From Comparing a German and an Australian Sample

Job crafting refers to the act of employees actively altering work aspects to better suit their values and interests. Slemp and Vella-Brodrick (2013) proposed a Job Crafting Questionnaire (JCQ) in English consisting of three facets: task crafting, cognitive crafting, and relational crafting. This is in line with the original conceptualization of job crafting by Wrzesniewski and Dutton (2001). However, there has not yet been an evaluated German translation of this measure. Therefore, this paper aims at evaluating the psychometric properties of scores from a German translation of the JCQ, using the original Australian dataset and a German sample of 482 employees. Our findings showed first evidence for the reliability and validity of the scores. We also extend prior research and include creative self-efficacy in the nomological network of job crafting. Importantly, strong factorial measurement invariance was demonstrated, allowing for comparisons between the job crafting scores of German- and English-speaking samples. Based on this example, we highlight the importance of enriching measurement invariance tests by including other key constructs. Our results suggest that the German JCQ is an acceptable tool for measuring job crafting, as originally conceptualized by Wrzesniewski and Dutton (2001)

Comparative Gas Sorption and Cryoporometry Study of Mesoporous Glass Structure: Application of the Serially Connected Pore Model

Nitrogen sorption and melting and freezing of water in a small pore size mesoporous glass with irregular pore structure is studied. The analysis of the experimentally obtained data is performed using the recently developed serially connected pore model (SCPM). The model intrinsically incorporates structural disorder by introducing coupling between nucleation and phase growth mechanisms in geometrically disordered mesopore spaces. It is shown that, in contrast to the independent pore models prevailing in the literature, SCPM self-consistently describes not only boundary transitions, but also the entire family of the scanning transitions. The scanning behavior is shown to be very sensitive to microscopic details of the fluid phase distribution within the porous materials, hence can be used to check the validity of the thermodynamic models and to improve the structural analysis. We show excellent quantitative agreement between the structural information evaluated from the cryoporometry and gas sorption data using SCPM

Candidate Sequence Variants and Fetal Hemoglobin in Children with Sickle Cell Disease Treated with Hydroxyurea

Fetal hemoglobin level is a heritable complex trait that strongly correlates with the clinical severity of sickle cell disease. Only few genetic loci have been identified as robustly associated with fetal hemoglobin in patients with sickle cell disease, primarily adults. The sole approved pharmacologic therapy for this disease is hydroxyurea, with effects largely attributable to induction of fetal hemoglobin. In a multi-site observational analysis of children with sickle cell disease, candidate single nucleotide polymorphisms associated with baseline fetal hemoglobin levels in adult sickle cell disease were examined in children at baseline and induced by hydroxyurea therapy. For baseline levels, single marker analysis demonstrated significant association with BCL11A and the beta and epsilon globin loci (HBB and HBE, respectively), with an additive attributable variance from these loci of 23%. Among a subset of children on hydroxyurea, baseline fetal hemoglobin levels explained 33% of the variance in induced levels. The variant in HBE accounted for an additional 13% of the variance in induced levels, while variants in the HBB and BCL11A loci did not contribute beyond baseline levels. These findings clarify the overlap between baseline and hydroxyurea-induced fetal hemoglobin levels in pediatric disease. Studies assessing influences of specific sequence variants in these and other genetic loci in larger populations and in unusual hydroxyurea responders are needed to further understand the maintenance and therapeutic induction of fetal hemoglobin in pediatric sickle cell disease

The brain in myotonic dystrophy 1 and 2: evidence for a predominant white matter disease

Myotonic dystrophy types 1 and 2 are progressive multisystemic disorders with potential brain involvement. We compared 22 myotonic dystrophy type 1 and 22 myotonic dystrophy type 2 clinically and neuropsychologically well-characterized patients and a corresponding healthy control group using structural brain magnetic resonance imaging at 3 T (T1/T2/diffusion-weighted). Voxel-based morphometry and diffusion tensor imaging with tract-based spatial statistics were applied for voxel-wise analysis of cerebral grey and white matter affection (Pcorrected < 0.05). We further examined the association of structural brain changes with clinical and neuropsychological data. White matter lesions rated visually were more prevalent and severe in myotonic dystrophy type 1 compared with controls, with frontal white matter most prominently affected in both disorders, and temporal lesions restricted to myotonic dystrophy type 1. Voxel-based morphometry analyses demonstrated extensive white matter involvement in all cerebral lobes, brainstem and corpus callosum in myotonic dystrophy types 1 and 2, while grey matter decrease (cortical areas, thalamus, putamen) was restricted to myotonic dystrophy type 1. Accordingly, we found more prominent white matter affection in myotonic dystrophy type 1 than myotonic dystrophy type 2 by diffusion tensor imaging. Association fibres throughout the whole brain, limbic system fibre tracts, the callosal body and projection fibres (e.g. internal/external capsules) were affected in myotonic dystrophy types 1 and 2. Central motor pathways were exclusively impaired in myotonic dystrophy type 1. We found mild executive and attentional deficits in our patients when neuropsychological tests were corrected for manual motor dysfunctioning. Regression analyses revealed associations of white matter affection with several clinical parameters in both disease entities, but not with neuropsychological performance. We showed that depressed mood and fatigue were more prominent in patients with myotonic dystrophy type 1 with less white matter affection (early disease stages), contrary to patients with myotonic dystrophy type 2. Thus, depression in myotonic dystrophies might be a reactive adjustment disorder rather than a direct consequence of structural brain damage. Associations of white matter affection with age/disease duration as well as patterns of cerebral water diffusion parameters pointed towards an ongoing process of myelin destruction and/or axonal loss in our cross-sectional study design. Our data suggest that both myotonic dystrophy types 1 and 2 are serious white matter diseases with prominent callosal body and limbic system affection. White matter changes dominated the extent of grey matter changes, which might argue against Wallerian degeneration as the major cause of white matter affection in myotonic dystrophies