Stacked Modulation Formats Enabling Highest-Sensitivity Optical Free-Space Communications

Die vorliegende Arbeit befasst sich mit hochempfindlichen optischen Kommunikationssystemen, wie sie z.B. bei Intersatellitenlinks verwendet werden. Theoretische Überlegungen zur Steigerung der Empfängerempfindlichkeit werden mit Simulations- und Messergebnissen ergänzt und verifiziert. Auf Grund der steigenden Nachfrage nach optischen Links zwischen Satelliten stellt sich die Frage, was sind geeignete Eckparameter, um ein solches System zu beschreiben. Die gigantischen Datenmengen, die von diversen Messgeräten, wie z.B. hochauflösende Kameras auf einem Satelliten generiert werden, bringen die Kapazitäten klassischer HF-Datenlinks an ihre Grenzen. Hier können optische Kommunikationssysteme auf Grund ihrer hohen Trägerfrequenz im Infrarotbereich sehr hohe Datenraten im Terabit/s Bereich ermöglichen. Systeme mit Radiowellen im GHz Bereich als Trägerfrequenz sind hier deutlich limitierter. [7] Linkdistanz, verfügbare Leistung, Pointinggenauigkeit und verfügbare Antennengröße sind einige Parameter, die einen wichtigen Einfluss auf die Leistungsfähigkeit des Systems haben. Je größer die Distanz und desto kleiner die verfügbare Antennengröße sowohl am Sender als auch am Empfänger sind, desto weniger Signalleistung wird den Detektor erreichen. Nimmt man dann noch ungenaues Pointing hinzu, d.h. Sender und Empfänger sind nicht exakt aufeinander ausgerichtet, treten zusätzliche Verluste auf. [7] Ziel dieser Arbeit ist es, ein vereinfachtes System zu implementieren und zu testen, das mit möglichst wenigen Photonen pro Bit bei einer gegebenen Bitfehlerwahrscheinlichkeit bei einer möglichst hohen Datenrate arbeiten kann. Hierfür werden alle Freiheitsgrade einer optischen Welle zur Modulation verwendet, um mit sog. „Stapeln“ von Modulationsformaten eine Empfindlichkeitssteigerung zu erreichen. Die Amplitude des Signals wird durch Pulspositionsmodulation (PPM) moduliert, wobei das zeitlich variable Vorhandensein eines Pulses innerhalb des Symbols die Information enthält. Dieses Modulationsformat weist bis dato die höchste Empfindlichkeit in Literatur und Experimenten auf [4]. Je mehr Möglichkeiten es gibt, einen Puls in einem Symbol zu platzieren, desto höher ist die zu erwartende Empfindlichkeit des Systems. Mit anderen Worten: Steigert man die zeitliche Dauer eines PPM-Symbols, so wächst ebenfalls die Empfängerempfindlichkeit. Da bei diesem Ansatz die Datenrate sinkt, wird in dieser Arbeit eine andere Methode vorgestellt, die Empfindlichkeit eines Übertragungssystems zu steigern, ohne die Symbollänge unnötig in die Länge zu ziehen. Diese Arbeit befasst sich mit dem Stapeln (sog. „Stacking“) von Modulationsformaten, in dem neben der Amplitudenmodulation weitere Freiheitsgrade, wie die Frequenz, Phase und Polarisation geschickt genutzt werden. Bei der Frequenzumtastung (FSK) wird die optische Frequenz je nach Symbol um ein gewisses Maß verschoben. Bei der polarisations-geschalteten Quadratur-Phasenumtastung (PS-QPSK) werden sowohl die Phase, als auch die Polarisation der optischen Welle moduliert [12]. Als Endergebnis erhält man PPM-FSK-PS-QPSK als Modulationsformat mit hoher Empfindlichkeit. Gegenüber dem reinen PPM wird eine theoretische Empfindlichkeitssteigerung von mehr als 1 dB erreicht. Sowohl Simulations- als auch Messergebnisse bestätigen den Empfindlichkeitsgewinn

The ING tumor suppressors in cellular senescence and chromatin

<p>Abstract</p> <p>The Inhibitor of Growth (ING) proteins represent a type II tumor suppressor family comprising five conserved genes, <it>ING1 </it>to <it>ING5</it>. While ING1, ING2 and ING3 proteins are stable components of the mSIN3a-HDAC complexes, the association of ING1, ING4 and ING5 with HAT protein complexes was also reported. Among these the ING1 and ING2 have been analyzed more deeply. Similar to other tumor suppressor factors the ING proteins are also involved in many cellular pathways linked to cancer and cell proliferation such as cell cycle regulation, cellular senescence, DNA repair, apoptosis, inhibition of angiogenesis and modulation of chromatin.</p> <p>A common structural feature of ING factors is the conserved plant homeodomain (PHD), which can bind directly to the histone mark trimethylated lysine of histone H3 (H3K4me3). PHD mutants lose the ability to undergo cellular senescence linking chromatin mark recognition with cellular senescence. ING1 and ING2 are localized in the cell nucleus and associated with chromatin modifying enzymes, linking tumor suppression directly to chromatin regulation. In line with this, the expression of ING1 in tumors is aberrant or identified point mutations are mostly localized in the PHD finger and affect histone binding. Interestingly, ING1 protein levels increase in replicative senescent cells, latter representing an efficient pathway to inhibit cancer proliferation. In association with this, suppression of p33ING1 expression prolongs replicative life span and is also sufficient to bypass oncogene-induced senescence. Recent analyses of ING1- and ING2-deficient mice confirm a tumor suppressive role of ING1 and ING2 and also indicate an essential role of ING2 in meiosis.</p> <p>Here we summarize the activity of ING1 and ING2 as tumor suppressors, chromatin factors and in development.</p

Tunneling Time in Ultrafast Science is Real and Probabilistic

We compare the main competing theories of tunneling time against experimental measurements using the attoclock in strong laser field ionization of helium atoms. Refined attoclock measurements reveal a real and not instantaneous tunneling delay time over a large intensity regime, using two different experimental apparatus. Only two of the theoretical predictions are compatible within our experimental error: the Larmor time, and the probability distribution of tunneling times constructed using a Feynman Path Integral (FPI) formulation. The latter better matches the observed qualitative change in tunneling time over a wide intensity range, and predicts a broad tunneling time distribution with a long tail. The implication of such a probability distribution of tunneling times, as opposed to a distinct tunneling time, challenges how valence electron dynamics are currently reconstructed in attosecond science. It means that one must account for a significant uncertainty as to when the hole dynamics begin to evolve.Comment: 11 pages, 4 figure

Radiotherapy for lentigo maligna and lentigo maligna melanoma - a systematic review.

Lentigo maligna (LM) is the most common subtype of in situ melanoma und occurs frequently in the sun-exposed head and neck region in elderly patients. The therapeutic "gold standard" is surgical excision, as there is the risk of progression to invasive (lentigo maligna) melanoma (LMM). However, surgery is not feasible in certain patients due to age, comorbidities or patient preference. Radiotherapy using Grenz rays or superficial X-rays has been established as non-invasive alternative for the treatment of LM and LMM. We performed a systematic literature search of MEDLINE and Embase databases in September 2019 and identified 14 patient series using radiotherapy for LM or LMM. No prospective trials were found. The 14 studies reported a total of 1243 lesions (1075 LM and 168 LMM) treated with radiotherapy. Local recurrence rates ranged from 0 to 31% and were comparable to surgical series in most of the reports on radiotherapy. Superficial radiotherapy was prescribed in 5-23 fractions with a total dose of 35-57 Gy. Grenz ray therapy was prescribed in 42-160 Gy in 3-13 fractions with single doses up to 20 Gy. Cosmetic results were reported as "good" to "excellent" for the majority of patients.In conclusion, the available low-level evidence suggests that radiotherapy may be a safe and effective treatment for LM and LMM. Data from prospective trials such as the phase 3 RADICAL trial are needed to confirm these promising findings and to compare radiotherapy to other non-surgical therapies and to surgery

Age-related dissociation of sensory and decision-based auditory motion processing

Studies on the maturation of auditory motion processing in children have yielded inconsistent reports. The present study combines subjective and objective measurements to investigate how the auditory perceptual abilities of children change during development and whether these changes are paralleled by changes in the event-related brain potential (ERP). We employed the mismatch negativity (MMN) to determine maturational changes in the discrimination of interaural time differences (ITDs) that generate lateralized moving auditory percepts. MMNs were elicited in children, teenagers, and adults, using a small and a large ITD at stimulus offset with respect to each subject's discrimination threshold. In adults and teenagers large deviants elicited prominent MMNs, whereas small deviants at the behavioral threshold elicited only a marginal or no MMN. In contrast, pronounced MMNs for both deviant sizes were found in children. Behaviorally, however, most of the children showed higher discrimination thresholds than teens and adults. Although automatic ITD detection is functional, active discrimination is still limited in children. The lack of MMN deviance dependency in children suggests that unlike in teenagers and adults, neural signatures of automatic auditory motion processing do not mirror discrimination abilities. The study critically accounts for advanced understanding of children's central auditory development

High-Temperature Series Analysis of the Free Energy and Susceptibility of the 2D Random-Bond Ising Model

We derive high-temperature series expansions for the free energy and susceptibility of the two-dimensional random-bond Ising model with a symmetric bimodal distribution of two positive coupling strengths J_1 and J_2 and study the influence of the quenched, random bond-disorder on the critical behavior of the model. By analysing the series expansions over a wide range of coupling ratios J_2/J_1, covering the crossover from weak to strong disorder, we obtain for the susceptibility with two different methods compelling evidence for a singularity of the form $\chi \sim t^{-7/4} |\ln t|^{7/8}$, as predicted theoretically by Shalaev, Shankar, and Ludwig. For the specific heat our results are less convincing, but still compatible with the theoretically predicted log-log singularity.Comment: 19 pages, 6 Postscript figure

Sound Localization in Single-Sided Deaf Participants Provided With a Cochlear Implant

Spatial hearing is crucial in real life but deteriorates in participants with severe sensorineural hearing loss or single-sided deafness. This ability can potentially be improved with a unilateral cochlear implant (CI). The present study investigated measures of sound localization in participants with single-sided deafness provided with a CI. Sound localization was measured separately at eight loudspeaker positions (4°, 30°, 60°, and 90°) on the CI side and on the normal-hearing side. Low- and high-frequency noise bursts were used in the tests to investigate possible differences in the processing of interaural time and level differences. Data were compared to normal-hearing adults aged between 20 and 83. In addition, the benefit of the CI in speech understanding in noise was compared to the localization ability. Fifteen out of 18 participants were able to localize signals on the CI side and on the normal-hearing side, although performance was highly variable across participants. Three participants always pointed to the normal-hearing side, irrespective of the location of the signal. The comparison with control data showed that participants had particular difficulties localizing sounds at frontal locations and on the CI side. In contrast to most previous results, participants were able to localize low-frequency signals, although they localized high-frequency signals more accurately. Speech understanding in noise was better with the CI compared to testing without CI, but only at a position where the CI also improved sound localization. Our data suggest that a CI can, to a large extent, restore localization in participants with single-sided deafness. Difficulties may remain at frontal locations and on the CI side. However, speech understanding in noise improves when wearing the CI. The treatment with a CI in these participants might provide real-world benefits, such as improved orientation in traffic and speech understanding in difficult listening situations

Geschlechterverhältnisse als Machtverhältnisse - Einleitung

Scheele A, Bargetz B, Lepperhoff J, Ludwig G, Wilde G. Geschlechterverhältnisse als Machtverhältnisse. Einleitung. Femina Politica. 2017;26(1):9-23

Mental health problems in children of somatically ill parents, e.g. multiple sclerosis

Objectives: Based on the investigation of 144 families (144 patients affected by Multiple Sclerosis (MS), 109 partners, and 192 children) examined in three different European child and adolescent psychiatric University centres by means of questionnaires, we evaluated the prevalence of psychological symptoms in the offspring and associated risk factors such as duration and severity of the disease as well as depression of the ill and the healthy parent. Results: Indicate that the severe disease of MS is associated with depression of the ill and healthy parent. Ill parents, especially ill mothers, as well as depressed ill, or depressed healthy parents evaluate their children's mental health problems with a higher prevalence within the internalizing spectrum. Healthy parents report normal psychological adjustment of their children. If two parents present a depressive state, the prevalence of relevant psychological internalizing symptoms is twice or three times as high as the age norms. Conclusion: Children in families with a parent affected by MS and associated depression of the parental couple are at high risk of mental health problems, especially internalizing disorders. In focusing on the mental health of children one must also be aware of the potential opportunities to address the parents' own psychological need