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Molecular Zinc(II) Complexes for the CO₂/epoxide Copolymerisation
No full textIn this thesis, series of novel {ONO}-pincer zinc(II) complexes were synthesized and evaluated as catalysts for the copolymerization of CO₂ and cyclohexene oxide (CHO) under both high (50 bar) and ambient (1 bar) CO₂ pressures. Ligand backbone modifications with electron-donating and -withdrawing substituents were found to influence the catalytic performance significantly. The parent complex, 1H, exhibited the highest activity and chemoselectivity across all conditions. Methoxysubstituted complexes displayed enhanced selectivity and tunable activity, while bulky substituents resulted in diminished performance. Mechanistic investigations using NMR and mass spectrometry revealed cyclohex-2-en-1-olate and
cyclohexanolate as consistent end groups, prompting a new initiation pathway involving a C–H activation step. The addition
of benzyl alcohol as an external initiator improved both molecular weight control and polymer dispersity without
compromising selectivity. These findings underscore the critical role of ligand design and initiation chemistry in optimizing
zinc-based catalysts for sustainable CO₂ utilization.2026-06-1
Addressing Habits in Anorexia Nervosa
No full textAnorexia Nervosa (AN) is a mental disorder that affects up to 0.3% of men and 6.2%
of women worldwide and places a significant burden on the individual, their social
environment and the healthcare system. Although extensive research has examined potential
mechanisms underlying the maintenance of the disorder, our understanding remains limited.
This may account for the suboptimal outcomes of the psychotherapeutic approaches
developed to date. The disordered eating- and weight-related behaviors characterizing AN
often remain after treatment, which is closely associated with relapse. Regulating Emotions
and Changing Habits (REaCH), a novel behavioral treatment, specifically targets these
behaviors as a potentially maintaining mechanism and offers adaptive emotion regulation
strategies in their stead if needed. The efficacy of REaCH was tested in a randomized
controlled trial. 110 inpatients with AN were assigned to receive four weeks of either REaCH
or supportive psychotherapy (active control condition) as an add-on to treatment as usual.
Clinical outcome data was collected before and after treatment as well as at six-month
follow-up. There were no significant differences between treatments regarding trajectories of
weight, eating disorder pathology, food choice or habit strength. This may trace back to
behavioral changes caused by the inpatient setting, extensive treatment as usual and short
treatment duration. Difficulties in emotion regulation decreased more steeply in REaCH
patients, pointing towards a potential benefit of REaCH. Implications for clinical practice and
future research are discussed.2026-10-0
Die Entwicklung des klinischen Outcomes nach Schädel-Hirn-Trauma bei Patienten über 60 Jahren – Ein Vergleich zwischen einer aktuellen Patientenkohorte und einer früheren aus den 80er Jahren
No full textWith demographic aging, the incidence of traumatic brain injury (TBI) in older adults is increasing significantly. Elderly patients exhibit distinct risk profiles, different trauma mechanisms, and increased vulnerability. The aim of this dissertation was to analyze the clinical outcome of TBI patients over 60 years of age in a contemporary cohort and to compare these findings with a historical cohort from the late 1980s. A retrospective analysis was conducted on 1,023 patients aged ≥60 years who were treated at the University Medical Center Göttingen between 2008 and 2019, with outcomes measured using the Glasgow Outcome Scale. Demographic data, mechanisms of injury, diagnoses, and comorbidities were collected. The results were compared with a cohort of 174 patients treated between 1987 and 1989. Advanced age was significantly associated with poorer outcomes and higher mortality at all assessment points. Comorbidities and pre-injury functional impairments showed prognostic relevance. Falls were identified as the most common mechanism of trauma. In the historical comparison, despite a higher average age in the contemporary cohort, overall outcomes were not worse, indicating medical progress. The findings underscore the particular vulnerability of older TBI patients and the prognostic importance of age, comorbidities, and functional status. The growing significance of geriatric TBI necessitates age-adapted guidelines and specialized care structures.2026-02-1
Do capillary blood samples that are sent to a laboratory by mail provide results comparable to laboratory analyses from venous blood samples taken in a general practitioner’s office?
No full textEinleitung:
Kapillare Selbstblutentnahmen sind durch neue Oberarmgeräte durch die Patienten selbstständig möglich. Dank verbesserter Labormesstechnologie können aus kleinere Probevolumina von unter einem Milliliter eine Vielzahl an Laboranalysen durchgeführt werden.
Methoden:
Zur Untersuchung der Vergleichbarkeit von Laborergebnissen, die aus üblichen venösen Blutentnahmen gewonnen worden sind und Kapillarblut wurde eine prospektive bizentrische Querschnittsstudie (Blood-it-Yourself-Studie) in 2 Hausarztpraxen in Thüringen und Niedersachsen im Zeitraum Februar bis Juni 2024 durchgeführt. Es wurden insgesamt 109 Patienten eingeschlossen, wovon 106 Blutproben ausgewertet werden konnten. Einschlusskriterien waren die Indikation zur Blutentnahme und Alter über 18 Jahre. Die Ausschlusskriterien umfassten: fehlende Einwilligungsfähigkeit, Kontraindikationen gegen kapilläre Blutentnahmen am Oberarm wie z.B. Hauterkrankungen oder das Vorhandensein einer Notfallsituation, die unmittelbares Handeln erforderte.
Ergebnisse:
Venöse und kapilläre Blutproben korrelieren in einem guten Maße für die gemessenen Laborwerte (HbA1c, LDL, HDL, Cholesterol, Harnsäure, Kreatinin, CRP, ALT, AST, GGT, Ferritin, TSH), wobei HbA1c die stärkst Korrelation zeigte und AST die Schwächste. Die Schmerzen der kapillären Blutprobengewinnung wurden statistisch signifikant geringer bewertet im Vergleich zur venösen Blutgewinnung. Es konnte kein Probenverlust durch den Postversand festgestellt werden.
Zur Beurteilung der Machbarkeit, der System usability score (SUS) verwendet, welcher im Mittel 86,22 (SD=14,12) betrug. Ängstliche Patienten und Patienten mit niedriger Bildung zeigten einen niedrigeren SUS-Score. In bivariater Analyse zeigten Patienten mit Diabetes ein niedrigeres Probevolumen als Patienten ohne. Allerdings war dieser Unterschied in der multivariaten Analyse nicht mehr signifikant.
Schlussfolgerungen:
Wir konnten zeigen, dass Patienten in der Hausarztpraxis in der Lage sind kapilläre Selbstblutentnahmen durchzuführen. Die Einflüsse des Postversandes sind gering, sodass wir für die gemessenen Laborparameter Kapillarblut als vergleichbares Probenmaterial zu venösem Blut ansehen.Introduction:
New upper-arm devices allow patients to collect capillary self-blood samples on their own. Thanks to improved laboratory measurement technologies in recent decades, much smaller sample volumes are now required, allowing several laboratory parameters to be analyzed from less than one milliliter of sample volume.
Methods:
To examine the comparability of laboratory results obtained from standard venous blood draws and capillary blood samples, a prospective, bicentric cross-sectional study (the Blood-it-Yourself study) was conducted in two general practices in Thuringia and Lower Saxony between February and June 2024. A total of 109 patients were enrolled, of whom 106 blood samples could be evaluated. Inclusion criteria were an indication for blood sampling and age over 18 years. Exclusion criteria included lack of capacity to provide informed consent, contraindications to capillary upper-arm blood collection such as skin disorders, or the presence of an emergency situation requiring immediate action.
Results:
Venous and capillary blood samples showed good correlation for the laboratory parameters measured (HbA1c, LDL, HDL, cholesterol, uric acid, creatinine, CRP, ALT, AST, GGT, ferritin, TSH), with HbA1c exhibiting the strongest correlation and AST the weakest. Pain associated with capillary blood collection was rated statistically significantly lower compared to venous blood collection. No sample loss occurred during postal shipment.
To assess feasibility, the System Usability Scale (SUS) was used, yielding an average score of 86.22 (SD = 14.12), which corresponds to good user-friendliness. Anxious patients and those with lower educational levels showed lower SUS scores. In bivariate analysis, patients with diabetes produced lower sample volumes than those without diabetes; however, this difference was no longer significant in multivariate analysis.
Conclusions:
We were able to show that patients in general practice are capable of performing capillary self–blood collection. The effects of postal shipment are minimal, allowing us to consider capillary blood a sample material comparable to venous blood for the laboratory parameters measured.2026-02-2
Langfristiger Effekt einer Lungenarterienembolie auf das Mortalitätsrisiko
No full textWhile numerous studies have investigated short-term outcomes after pulmonary embolism (PE), long-term mortality remains insufficiently studied. The objectives were investigate long-term outcomes in an unselected cohort of patients with PE. Therefore, a total of 896 consecutive patients with PE enrolled in a single-center registry between May 2005 and December 2017 were followed up for up to 14 years. The observed mortality rate was compared with the expected rate in the general population.
The total follow-up time was 3908 patient-years (median, 3.1 years). The 1- and 5-year mortality rates were 19.7% (95% CI, 17.2%-22.4%) and 37.1% (95% CI, 33.6%-40.5%), respectively. The most frequent causes of death were cancer (28.5%), PE (19.4%), infections (13.9%), and cardiovascular events (11.6%). Late mortality (after >30 days) was more frequent than expected in the general population, a finding that was consistent in patients without cancer (the 5-year standardized mortality ratios were 2.77 [95% CI, 2.41-3.16] and 1.80 [95% CI, 1.50-2.14], respectively). Active cancer was the strongest risk factor for death between 30 days and 3 years (hazard ratio [HR], 6.51; 95% CI, 4.67-9.08) but was not associated with later mortality. Death after >3 years was predicted by age (HR, 1.86; 95% CI, 1.51-2.29 per decade), chronic heart failure (HR, 1.66; 95% CI, 1.02-2.70), and anemia (HR, 1.62; 95% CI, 1.09-2.41).
In conclusion, the risk of mortality in patients with PE remained elevated compared with that in the general population throughout the follow-up period. The main driver of long-term mortality during the first 3 years was cancer. After that, mortality was predicted by age, chronic heart failure, and anemia.2026-02-1
Der Effekt statischer Magnetfelder auf die Erregbarkeit der Hirnrinde bei Patient*innen mit amyotropher Lateralsklerose
No full textAmyotrophic lateral sclerosis (ALS) is a rare, complex, and progressive neurological disorder that on average leads to death within two to four years after diagnosis. To date, only a limited number of therapeutic options are available. Therefore, treatment is predominantly symptomatic. Particularly in the early stages of the disease, cortical excitability of the motor cortex is increased. Transcranial static magnetic stimulation (tSMS) represents a technically simple, non-invasive method that has been shown in studies of healthy participants to reduce cortical excitability.
We therefore conducted an interventional pilot study investigating the application of transcranial static magnetic stimulation in patients with ALS. The aim of the study was to determine whether a ten-minute application of tSMS over the primary motor cortex (M1) can induce changes in cortical excitability in patients with ALS and whether this method could represent an acceptable approach for potentially regular and self-administered home stimulation. Changes in cortical excitability induced by tSMS were assessed using transcranial magnetic stimulation.
Complete datasets from 13 patients were available for analysis (mean age: 61.3 ± 7 years; mean ALSFRS-R score: 38.7 ± 4.5 points). In multivariate time-series analyses of both mean and median motor-evoked potential (MEP) amplitudes, neither the factor stimulation, nor time, nor the interaction between stimulation and time had a significant effect on MEPs. In contrast, the concept of home-based stimulation was perceived by most patients as a feasible and low–side-effect therapeutic option.
Given the generally high variability associated with non-invasive brain stimulation techniques and additional limitations of this pilot study (e.g. small sample size and heterogeneity in disease progression), further clinical investigations may be warranted to evaluate the potential therapeutic effects of tSMS more thoroughly and to develop specific protocols for future studies.2026-03-1
Single-center cluster analysis
No full textIn der klinischen Notfall- und Akutmedizin wurden in der letzten Dekade überwiegend theoretische Modelle mit monodimensionalen Kriterien für die Indikation zur stationären Aufnahme von Notfallpatienten entwickelt. Ziel der retrospektiven Studie war es, operationalisierbare Kriterien für eine stationäre Behandlungsnotwendigkeit in der Zentralen Notaufnahme (ZNA) zu definieren.
Hierzu wurden die Daten von mehr als 35000 Notfällen der ZNA der Universitätsmedizin Göttingen (UMG) im Zeitraum Januar 2016 - Mai 2018 mit Hilfe der im Verlauf resultie-renden ICD-10-GM-Diagnosen ausgewertet. Multimorbidität wurde bei Vorliegen von mindestens n = 5 Diagnosen angenommen. Mittels Clusterung erfolgte eine statistische Analyse in Bezug auf die Wahrscheinlichkeit einer stationären Aufnahme bzw. einer weiteren ambulanten Versorgung.
Eine stationäre Aufnahme erfolgte bei 81 % aller Notfälle, davon wurden 55 % (n = 15.652) als Multimorbide klassifiziert. Dieser Anteil lag bei ambulanten Notfällen lediglich bei 1 % (n = 64). Stationäre Fälle waren statistisch hochsignifikant älter als ambulante Fälle (68,7/60,8 J.) (p<0,001; 95 %-CI [3.73, 12.18]; t(63,5)=3,76) und umfassten daher etwa zur Hälfte typisch geriatrische Fälle. Nach Zusammenfassung der häufigsten ICD-Diagnosen a priori in 112 Diagnose-Subcluster sowie hierarchischer Clusteranalyse mittels Dendrogramm wurden für die stationären Fälle mit Multimorbidität n = 13 Cluster (u.a. Cluster 3 schwere Pneumonien mit kardialer Erkrankung und akutem Nierenversagen, Cluster 11 systemische Infektionen) und für die ambulanten Fälle n = 7 Cluster identifi-ziert (u.a. Cluster 1 hämatoonkologische Erkrankungen). Mit einer Krankenhausverweildauer von mehr als 15 Tagen verblieben multimorbide Fälle aus Cluster 11 am längsten im Krankenhaus. Die längste Verweildauer in der ZNA wiesen die stationären Fälle mit Multimorbidität aus dem Cluster 7 auf (Median 7,0 Stunden). Ambulante Fälle mit Multimorbidität verblieben höchstens 3,2 Stunden in der ZNA (Cluster 5).
In dieser Studie konnten für Multimorbidität typische Diagnosekombinationen in Form von Clustern identifiziert werden. Dabei zeigte sich für stationäre Multimorbide ein heterogenes Mischbild an Diagnosen, während bei ambulanten Multimorbiden vor allem hämatologische Malignome im Vordergrund standen. Die ZNA-Verweildauer stationärer Fälle mit Multimorbidität war mehr als doppelt so lang wie bei ambulanten Fällen. Mit der Entwicklung solcher multidimensionaler Multimorbiditäts-Scores könnte zukünftig eine raschere Indikationsstellung zur stationären Aufnahme und damit eine Verkürzung der Verweildauer sowie eine Verbesserung des Patientenflusses in der ZNA erzielt werden.Background
Parallel to demographic trends, an increase of multimorbid patients in emergency and acute medicine is prominent. To define easily applicable criteria for the necessity of inpatient admission, a hierarchical cluster analysis was performed.
Methods
In a retrospective, single-center study data of n = 35,249 emergency cases (01/2016–05/2018) were statistically analyzed. Multimorbidity (MM) was defined by at least five ICD-10-GM diagnoses resulting from treatment. A hierarchical cluster analysis was performed for those diagnoses initially summarized into 112 diagnosis subclusters to determine specific clusters of in- and outpatient cases.
Results
Hospital admission was determined in 81.2% of all ED patients (n = 28,633); 54.7% of inpatients (n = 15,652) and 0.97% of outpatient cases (n = 64) met the criteria for multimorbidity and the age difference between them was highly significant (68.7/60.8 years; p < 0.001). Using a hierarchical cluster analysis, 13 clusters with different diagnoses were identified for inpatient multimorbid patients (MP) and 7 clusters with primarily hematological malignancies for outpatient MP. The length of stay in the ED of inpatient MP was more than twice as long (max. 8.3 h) as for outpatient MP (max. 3.2 h.).
Conclusions
The combination of diagnoses typical for MM were characterized as clusters in this study. In contrast to single or combined single diagnoses, the statistically determined characterization of clusters allows for a significantly more accurate prediction of ED patients’ disposition as well as for economic process allocation.2026-03-0
The effect of parasitic plants on host plant immunity against microbial pathogens
No full textPlants in natural environments are frequently exposed to multiple biotic and abiotic stresses, and their combined effects often trigger complex and non-additive physiological and molecular responses (Suzuki et al., 2014). Among these, parasitic plants impose a major biotic stress, establishing haustoria connections with host roots to extract water, nutrients, and signalling molecules (Albert et al., 2021; Yoshida et al., 2016). Parasitism may profoundly influence the host’s immune competence and interactions with other microbial pathogens. However, the impact of parasitic plants on host immune regulation against microbial infections remains largely unexplored.
This study examined the impact of parasitism by the facultative hemiparasite Phtheirospermum japonicum on the immune responses of Arabidopsis thaliana to microbial pathogens. Parasitization assays revealed that A. thaliana plants parasitized by P. japonicum exhibited a significant reduction in growth and biomass, suggesting a substantial physiological burden for the host. To examine whether this effect extends to immune regulation, early pattern-triggered immunity (PTI) responses were analyzed using flg22 and chitin treatments. Measurements of reactive oxygen species (ROS) production, Mitogen-Activated Protein Kinase (MAPK) phosphorylation, and defence gene expression revealed that parasitized plants exhibited significantly reduced PTI activation compared to unparasitized controls.
To determine whether this compromised immunity translated into altered disease susceptibility, infection assays were conducted using the hemibiotrophic bacterium Pseudomonas syringae pv. tomato DC3000 and the necrotrophic fungus Botrytis cinerea strain B05.10. Parasitized A. thaliana plants exhibited hypersusceptibility to both pathogens, characterized by higher bacterial titers and larger necrotic lesions compared to unparasitized plants, confirming a broad suppression of immune competence. To elucidate the molecular mechanisms underlying this immune attenuation, transcriptomic profiling (RNA-seq) was performed on parasitized and unparasitized A. thaliana plants treated with flg22 or infected with Pst DC3000. The results revealed that P. japonicum parasitism markedly suppressed flg22- and Pst-triggered transcriptional responses. In parasitized plants, PTI-associated genes and growth-related pathways were downregulated, while nutrient starvation pathways were induced. Moreover, infection with Pst DC3000 triggered strong phosphate starvation responses and repressed key defence pathways involving salicylic acid (SA), jasmonic acid (JA), and glucosinolate biosynthesis. Phosphate starvation is well documented to suppress plant immunity, a phenomenon that appears to be evolutionarily conserved across multiple plant species, where nutrient deprivation often compromises defence signalling and increases susceptibility to pathogens.
Finally, to identify which phytohormone signalling networks are altered during parasitism, phytohormone reporter lines of A. thaliana were used to monitor SA, JA, JA/ethylene (JA/ET), and abscisic acid (ABA) activity in roots. Parasitism induced strong ABA signalling, whereas SA and JA/ET pathways remained largely unresponsive. Interestingly, JA reporters revealed a complex pattern, with induction of VSP2 and JAZ9 but no activation of AOS in the host roots. As previous transcriptomic studies have shown AOS induction in P. japonicum haustoria during parasitism (Kokla et al., 2022), this suggests that the observed JA response may originate in the parasite rather than the host, although this remains to be confirmed.
Collectively, this study provides novel insights into how P. japonicum modulates host immunity and nutrient signalling. The findings highlight that parasitism induces nutrient starvation responses, particularly phosphate limitation, which are closely linked to suppression of immune signalling. This work underscores the intricate trade-offs between growth, defence, and nutrient acquisition in plants subjected to combined stresses, including parasitism and pathogen attack.2026-12-0
Zwischen Selbstständigkeit und Zusammenhalt: Die Dynamik von Autonomie und emotionaler Verbundenheit in Familien mit essgestörten Kindern
No full textThis monocentric observational study, conducted at the Department of Psychosomatic Medicine and Psychotherapy at University Medical Center Göttingen, investigated the interplay between family relationships and eating disorders in a sample of 313 outpatient individuals diagnosed with anorexia nervosa or bulimia nervosa. Using a retrospective design, data were collected between 1991 and 2017 and captured participants’ subjective perceptions of autonomy and emotional connectedness within their primary families. Symptom severity was assessed using the Global Severity Index (GSI) of the Symptom Checklist-90-R, and family relationship characteristics were measured with the Subjektives Familienbild questionnaire. The study aimed to improve understanding of potentially pathogenetically relevant relational variables in anorexia and bulimia, an area that remains insufficiently explored.
Psychometric analyses revealed significant differences between diagnostic groups in perceived family autonomy (potency) and emotional connectedness (valence). Participants with bulimia nervosa reported generally more negative evaluations of both dimensions compared with those with anorexia nervosa. Logistic regression analyses confirmed that perceived valence and potency significantly differentiated between the two diagnostic groups.
Across the full cohort, significant negative correlations were observed between age, symptom burden, and overall family autonomy scores. When stratified by diagnosis, a negative association between age and perceived autonomy was found only in the anorexia nervosa group, whereas symptom severity was inversely associated with perceived autonomy in both groups. Regarding emotional connectedness, age, body mass index, and symptom severity were negatively correlated with perceived family valence. Notably, inverse associations of psychosomatic distress (GSI) and age with family connectedness were evident exclusively among participants with bulimia nervosa.
Overall, this study identified significant associations between subjective perceptions of family connectedness and individual autonomy, adjusted for relevant psychometric indicators, in a large and heterogeneous outpatient eating-disorder sample. Further research is needed to validate these findings and to clarify the psychological mechanisms underlying the observed relationships.2026-02-1
Measuring and Optimizing Peer-to-Peer Networks: A Case Study of the InterPlanetary File System
No full textDie Entwicklung des Internets von einem dezentralen Netzwerk von Netzwerken hin zu einer konzentrierten Kontrolle durch eine Handvoll Plattformen hat zu systemischer Fragilität und Machtungleichgewichten geführt.
In den letzten Jahrzehnten hat sich das Internet von seinen ursprünglichen Idealen eines offenen, dezentralen Netzwerks stetig entfernt. Nutzerinteraktionen konzentrieren sich zunehmend in einer Handvoll Plattformen was zu systematischer Fragilität und mit einer Bündelung von Macht einhergeht. Die Decentralized Web Bewegung reagiert darauf mit der Entwicklung von alternativen Systemen, die auf einer Peer-to-Peer Architektur beruhen und damit zentralisierte Komponenten obsolet machen. Diese Systeme haben jedoch einen grundlegenden Nachteil gegenüber ihren zentralisierten Gegenparts: Zentralisierte Plattformen verfügen über umfassende Einblicke in jegliche Nutzerinteraktionen, die auf ihren Plattformen stattfinden und können diese Erkenntnisse nutzen, um Leistungsengpässe zu identifizieren und wirksame Optimierungen umzusetzen. Dezentralen Systemen fehlen häufig vergleichbare Einblicke in das Verhalten der Netzwerkteilnehmer. Dieses inhärente architektonische Wissensungleichgewicht der Möglichkeit der Datenerhebung führt zu kritischen Lücken im Verständnis des Netzwerkverhaltens und der Identifizierung von Leistungsengpässen, was wiederum den praktischen Einsatz von Peer-to-Peer Systemen erschwert.
Die Dissertation befasst sich mit dieser Herausforderung durch die messbasierte Charakterisierung und Optimierung des InterPlanetary File Systems (IPFS), einem bekannten Peer-to-Peer Netzwerk. Anstelle einer reinen dezentralen Peer-to-Peer Architektur stellt IPFS eine hybride Architektur dar, in der zentralisierte Infrastruktur mit vollständig dezentralen Protokollen koexistiert, wodurch eine fragmentierte Sichtbarkeit über Architekturgrenzen hinweg entsteht. In dieser Arbeit werden Messmethoden entwickelt, die diese fragmentierten Beobachtungen zu einem umfassenden Netzwerkverständnis zusammenfassen und empirische Erkenntnisse für eine gezielte Protokolloptimierung nutzen. Die Untersuchung umfasst drei kritische Messbereiche: Die Charakterisierung der Netzwerktopologie und der Content-Routing-Performance. Diese identifizierte die Distributed Hash Table PUT Latenz als kritischen Engpass mit mittleren Latenzen von 27,7 Sekunden aus Europa. Die Erhebung der Peer-Konnektivität und NAT-Traversal-Effektivität bei der eine Erfolgsquote von 70% für dezentrale Network Address Translation Traversal bei 4,4 Millionen Datenpunkten aus 167 Ländern gemessen wurde. Die Analyse von Nutzungsmustern und Inhaltskontrollen ergab eine Konzentrations-Replikations-Dualität: Einzelne Netzwerkteilnehmer stellen bis zu 63% der als problematisch markierten Inhalte bereit, doch die weit verbreitete Replikation stellte sicher, dass nur 0,1% der Inhalte einzeln gehostet blieben, was koordinierte Löschmaßnahmen erschwerte.
Insbesondere die Messung der Netzwerktopologie und der Content-Routing-Performance ermöglichte die Entwicklung und den Einsatz von Optimistic Provide, einer abwärtskompatiblen Protokolloptimierung, die erhebliche Leistungsverbesserungen erzielt:
PUT-Latenz von unter einer Sekunde für 90% der Operationen bei gleichzeitiger Reduzierung des Netzwerk-Overheads um 40%. Die Ergebnisse zeigen, dass das systematische Zusammentragen von fragmentierten Beobachtungen evidenzbasierte Optimierungen ermöglicht. Dies erhöht die Realisierbarkeit von Peer-to-Peer-Systemen als Alternative zu zentralisierten Architekturen.The Internet's transformation from a decentralized network of networks into a landscape dominated by centralized platforms has created systemic risks including infrastructure fragility, censorship vulnerabilities, and concentrated control. While decentralized peer-to-peer systems offer architectural alternatives, they suffer from a fundamental architectural knowledge imbalance: centralized platforms observe all user interactions enabling sophisticated optimization, whereas peer-to-peer networks lack unified observability, hindering both performance analysis and targeted improvements.
This dissertation addresses this challenge through comprehensive characterization and optimization of the InterPlanetary File System (IPFS), a prominent peer-to-peer storage network. IPFS's hybrid architecture of combining peer-to-peer networking with strategic centralized components creates fragmented visibility where different subsystems offer complementary but partial vantage points. The research develops measurement methodologies that synthesize these fragmented observations into comprehensive network understanding. It then leverages empirical insights for a targeted protocol optimization.
The investigation spans three critical measurement domains. Network topology and content routing performance characterization identified Distributed Hash Table publication latency as the critical bottleneck, with median latencies of 27.7 seconds from Europe. Peer connectivity and Network Address Translation traversal measurements through a novel honeypot methodology established a 70% success rate for decentralized hole-punching across 4.4 million measurements from 167 countries and 85k networks. Usage patterns and content governance analysis revealed a concentration-replication duality where single peers hosted up to 63% of denylist content yet widespread replication ensured only 0.1% of content remained uniquely hosted, complicating coordinated takedown efforts.
IPFS' systematic characterization enabled the design and deployment of Optimistic Provide, a backward-compatible protocol optimization achieving order-of-magnitude performance improvements: sub-second publication latency for 90\% of operations while reducing network overhead by 40%. The research demonstrates that systematic synthesis of partial observations can overcome the architectural knowledge imbalance, enabling evidence-based optimizations that enhance peer-to-peer systems' viability as alternatives to centralized architectures.2026-01-2