Scientific publications of the Saarland University
Not a member yet
14321 research outputs found
Sort by
Control strategies for heat pumps in a residential area under consideration of system operator benefits and grid stability
Get PDFThe energy sector faces challenges due to the increasing use of weather-depending renewables in power generation. The resulting fluctuations must be balanced through storage technologies and Demand Side Management
(DSM) methods. Heat pumps are generally recognized as shiftable loads for DSM. More and more heat pump
manufacturers in Germany are using the Smart-Grid- (SG-) Ready interface, which enables grid operators on the
one hand and system operators on the other hand to control heat pumps for the purpose of DSM aiming at either
grid power balancing (grid operator friendly) or to increase the self-consumption rate of the residential energy
system (system operator friendly). The presented work aims at a compromise between those two goals. To this
end, different control strategies for SG-Ready enabled solar and heat pump systems are implemented in a simulation framework and evaluated for a residential area using different key performance indicators. The results
show that a control strategy based on a dynamic price signal (PRBC2) with rule-based control and well-chosen
switching points, taking into account considered building energy systems and environmental conditions used
here, represents the best compromise between system operator friendly behavior and grid operator serviceability. The choice of switching points for the heat pump in the course of the price signal is crucial here, and must
take into account the consumption and generation profiles of the local residential areas. The fulfillment value of
the key indicators considered here for the representative residential area is 63.9%, whereas the value with the
reference operating strategy, in which the heat pump is operated exclusively in SG-Ready Mode 2, is only 50.6%
Relationship between serum estradiol level, ultrasound follicle count, number of oocytes retrieved and their influence on IVF/ICSI treatment outcomes: a retrospective cross-sectional study
Get PDFThis retrospective cross-sectional study investigates determinants on follicular
development, oocyte retrieval and pregnancy outcome. It assessed the clinical
practicability of monitoring parameters in relation to predict a successful
treatment. Analysis of serum-estradiol (E2), sonographic follicle count, number
of oocytes and optimizable parameters have therefore been carried out based on
patient files from the IVF outpatient clinic at the Department of Gynecology,
Obstetrics and Reproductive Medicine, Homburg/Saar, Germany.
Equidirectional connection occurred between serum-E2, sonographic follicle
count and number of oocytes (p < 0.001). There was no significant difference
between sonographic and punctured follicle count (p = 0.428), but between
sonographic/punctured follicle count and number of oocytes obtained (p < 0.01).
Increasing endometrial thickness was associated with increasing serum-E2 (p =
0.003) and number of oocytes (p
0.05). Additionally, age was inversely associated with sonographic follicle count
and number of oocytes (p 0.05). BMI, nicotine and
stimulation protocol had no association with the observed parameters (p > 0.05).
Mean differences in follicle numbers can be used for predicting expectable
numbers of oocytes. Due to comparable numbers of follicles visualized on the
day of ovulation induction and the number of follicles punctured, more emphasis
should be placed in optimizing oocyte retrieval procedures
Versatile High-Throughput Platform for Focused Ultrasound In Vitro Application
Get PDFFor the more efficient application of ultrasound in future therapies, fundamental research is needed on the mode of action of ultrasound on biological systems using
therapeutic frequencies. To address this need, a new versatile high-throughput platform
for focused ultrasound in vitro application was designed, developed, and characterized.
The applicator was aligned with the dimensions of a 96-well plate and frequencies commonly used in the therapeutic ultrasound range (0.5–2.0 MHz). Two different platform
configurations were developed: (a) a low-intensity version with 96 individual transducers
allowing dry coupling of the well plate; and (b) a high-intensity version with water cooling,
supporting parallel sonication of 32 out of 96 wells. The platforms were characterized by
performing an analysis of the homogeneity of the sound pressure and intensity, the impact
of filled volume per well, the cross-coupling effect between the wells, and the influence
of the well plate. The low-intensity design delivers pressure levels up to 605 kPa inside
the well with maximum ISPPA values between 0.78 and 12.38 W/cm2
. In contrast, the highintensity system achieves pressures up to 1460 kPa and a maximum ISPPA of 72 W/cm2
inside the wells. The successfully developed high-throughput platform supports parallelized sonication in standard, well-plate formats and is suitable for focused ultrasound
applications in vitro
Targeting pathological brain activity-related to neuroinflammation through scRNA-seq for new personalized therapies in Parkinson's disease
Get PDFForensic Insights into Borderline Personality Disorder: The Influence of Childhood Adversity and Antisocial Traits on Male Aggression and Violence
Get PDFAbstract
Despite borderline personality disorder's well-documented association with emo-tional instability and impulsive behaviors, its role in criminal careers, particularly in offenders with co-occurring antisocial traits, remains insufficiently explored.
This dissertation aims to investigate the complexities of aggression and violent crime in male offenders with borderline personality traits within a forensic setting.
Using a dataset of 315 male offenders, this study employed self-reported question-naires, clinical evaluations, and officially registered criminal records from the Ger-man Federal Central Register (Bundeszentralregister). Participants were evaluated for borderline traits (SCID-II), antisocial traits (PCL-R), aggression tendencies (Buss-Perry Aggression Questionnaire) and adverse childhood experiences (as defined by the ACE-Questionnaire) using validated psychometric assessments.
Through latent class analysis, three distinct offender profiles were identified: (1) a group exhibiting both borderline and antisocial traits, (2) a group primarily charac-terized by antisocial traits, and (3) a low-symptom group with minimal traits from either domain. The borderline-antisocial group exhibited the highest levels of ver-bal, physical, and indirect aggression, and had a significantly higher likelihood of violent crime compared to other groups. Moreover, age and adverse childhood ex-periences were found to significantly predict both higher levels of aggression as well as a greater likelihood of future violent offending, with the borderline antisocial class exhibiting the highest prevalence of adverse childhood experiences. This research contributes to the field of forensic psychiatry by clarifying how the dynamic between borderline and antisocial traits, under consideration of adverse childhood experiences, predicts patterns of aggression and criminal outcomes. The findings emphasize the need for targeted interventions addressing both personality pathology and childhood trauma in offenders.Zusamenfassung
Ziel der vorliegenden Dissertation war, die Komplexität von Aggression und Gewaltkri-minalität bei männlichen Straftätern mit borderline Persönlichkeitszügen im forensi-schen Kontext zu untersuchen. Trotz der bekannten Verbindung der Borderline-Persön-lichkeitsstörung mit emotionaler Instabilität und impulsivem Verhalten, bleibt ihre Rolle in kriminellen Karrieren unzureichend erforscht.
Mit einem Datensatz von 315 männlichen Straftätern wurden selbstberichtete Fragebö-gen, klinische Bewertungen und offiziell erfasste Strafregister aus dem deutschen Bun-deszentralregister verwendet. Die Teilnehmer wurden auf Borderline-Merkmale (SCID-II), antisoziale Merkmale (PCL-R), Aggressionstendenzen (Buss-Perry-Aggressionsfrage-bogen) und belastende Kindheitserfahrungen (gemäß ACE-Fragebogen) anhand vali-dierter psychometrischer Instrumente untersucht.
Durch latente Klassenanalyse konnten drei Täterprofile identifiziert werden: (1) eine Gruppe mit Borderline- und antisozialen Zügen, (2) eine Gruppe mit überwiegend anti-sozialen Zügen und (3) eine Kontrollgruppe mit minimalen Merkmalen aus beiden Be-reichen. Die Borderline-antisoziale Gruppe zeigte die höchsten Werte in verbaler, physi-scher und indirekter Aggression und wies eine signifikant höhere Wahrscheinlichkeit für gewalttätige Rückfälligkeit auf. Darüber hinaus erwiesen sich Alter und belastende Kindheitserfahrungen als signifikante Prädiktoren für sowohl erhöhte Aggressionsnei-gung als auch für zukünftige Gewaltstraftaten. Die Borderline-antisoziale Klasse wies dabei die höchste Prävalenz belastender Kindheitserfahrungen auf.
Diese Dissertation trägt zur Untersuchung der Dynamik zwischen Borderline- und anti-sozialen Merkmalen, beeinflusst durch frühe Lebensbelastungen bei und zeigt, wie Ag-gressionsmuster und kriminelles Verhalten vorhersagbar sein können. Die Ergebnisse unterstreichen ebenfalls die Notwendigkeit gezielter Interventionen, die sowohl Persön-lichkeitsstörungen als auch Kindheitstraumata berücksichtigen
Homogenisierung von Nanohydroxylapatitsuspensionen mittels Ultraschall
Get PDFOral hygiene products containing hydroxyapatite are becoming more and more important in dentistry as a biomimetic alternative to the common fluoride-containing products. The advantages of hydroxyapatite over fluorides have already been proven in various studies. However, scanning electron micrographs studies usually show an inhomogeneous distribution of agglomerated nanoparticles on the test surfaces used. This experimental work therefore addresses the question of whether ultrasonic treatment of hydroxyapatite suspensions enables a more homogeneous deposition of hydroxyapatite particles on various test surfaces. It can be assumed that a more homogeneous distribution increases the effectiveness of the hydroxyapatite treatment as well as the reproducibility of test series.
Suspensions were prepared from four different hydroxyapatite products and two solvents. These suspensions were treated with ultrasonic and then pipetted directly onto the adhesive foils of the SEM plates as well as onto bovine enamel test specimens. After different incubation times, the test surfaces were rinsed with sterile deionised water and then dried. Scanning electron microscopy images were taken to investigate the position of hydroxyapatite on the surface. The control group consisted of non-sonicated suspensions of the hydroxyapatite products, which were otherwise treated identically. The hydroxyapatite , which has the smallest particle size of the tested products, dissolved in sterile H2O, achieved the best result in all test series. Eprui 20 suspensions were therefore used for further in vivo tests.
For this purpose, a splint with bovine enamel test specimens was prepared and worn in the self-test. The hydroxyapatite suspension was rinsed for 1 min or 30 s and the test specimens were then examined. Since a pellicle is ubiquitous in the oral cavity, a 3 min incubated pellicle was also included in the test series. The result shows that a pellicle is indispensable as an adhesive layer on the enamel test specimens for the homogeneous deposition of hydroxyapatite particles. The test specimens without pellicles had little to no hydroxyapatite material on their surfaces. A rinsing time of 30 s was sufficient for all tests.
The conclusion of the work is thus that ultrasound can be used to loosen the hydroxyapatite particles from their agglomerates and achieve a homogeneous distribution. The smallest particles achieved the best results. Intraorally, a pellicle is necessary to guarantee adhesion of the hydroxyapatite particles and thus make the effect of homogenisation visible.Mit Hydroxylapatit versetzte Mundhygieneprodukte gewinnen in der Zahnmedizin als biomimetische Alternative zu den gängigen fluoridhaltigen Produkten immer mehr an Bedeutung. Die Vorteile von Hydroxylapatiten gegenüber Fluoriden wurden bereits in verschiedenen Studien belegt. Elektronenmikroskopische Aufnahmen in besagten Studien zeigen jedoch meist eine inhomogene Verteilung von agglomeriertem Hydroxylapatit auf den verwendeten Testoberflächen. Diese experimentelle Arbeit befasst sich daher mit der Fragestellung, ob eine Ultraschallbehandlung von Hydroxylapatit-Suspensionen eine homogenere Auflagerung der Nanopartikel auf diversen Testoberflächen ermöglicht. Es ist anzunehmen, dass eine homogenere Verteilung die Effektivität der Hydroxylapatit-Behandlung sowie die Reproduzierbarkeit von Versuchsreihen erhöht.
Aus vier verschiedenen Hydroxylapatit-Produkten und zwei Lösungsmitteln wurden Suspensionen hergestellt. Diese Suspensionen wurden anschließend mit Ultraschall behandelt und danach sowohl direkt auf die Haftfolien von REM- Probenteller, als auch auf bovine Schmelzprüfkörper aufpipettiert. Nach unterschiedlichen Inkubationszeiten wurden die Testoberflächen mit sterilem entionisiertem Wasser gespült und dann getrocknet. Um die Auflagerung von Hydroxylapatit auf der Oberfläche zu untersuchen, wurden rasterelektronenmikroskopische Bilder aufgenommen. Als Kontrollgruppe dienten nicht-beschallte Suspensionen der Hydroxylapatit-Produkte, mit denen ansonsten identisch verfahren wurde. Das Hydroxylapatit, welches die kleinste Partikelgröße der getesteten Produkte aufweist, gelöst in sterilem H2O, erzielte in allen Versuchsreihen das beste Ergebnis. Diese Suspensionen wurden daher für weiterführende in vivo Tests verwendet.
Hierfür wurde eine Schiene mit bovinen Schmelzprüfkörpern angefertigt und im Selbstversuch getragen. Mit der Hydroxylapatit-Suspension wurde 1 min bzw. 30 s gespült und die Prüfkörper anschließend untersucht. Da der Biofilm im Mundraum allgegenwärtig ist, wurde auch eine 3 min inkubierte Pellikel mit in die Versuchsreihen aufgenommen. Das Ergebnis zeigt, dass eine Pellikel als Haftschicht auf den Schmelzprüfkörpern für die homogene Auflagerung von Hydroxylapatit-Partikeln unabdingbar ist. Die Prüfkörper ohne Pellikel wiesen wenig bis kein Hydroxylapatit-Material auf ihren Oberflächen auf. Eine Spüldauer von 30 s war bei allen Versuchen ausreichend.
Fazit der Arbeit ist somit, dass mittels Ultraschalls die Hydroxylapatit-Partikel aus ihren Agglomeraten gelöst und eine homogene Verteilung erzielt werden kann. Die kleinsten Hydroxylapatit-Partikel erzielten die besten Ergebnisse. Intraoral ist eine Pellikel notwendig, um eine Anhaftung der Nanopartikel zu garantieren und somit den Effekt der Homogenisierung sichtbar zu machen
Stewards for future: Piloting a medical undergraduate elective on antimicrobial stewardship
Get PDFBackground: The rise of antimicrobial resistance as leading infection-related cause of death will necessitate trans-sectoral efforts on a global level. While many antimicrobial stewardship (AMS) incentives target healthcare workers, addressing undergraduates offers new and hitherto neglected opportunities.
Methods: We describe the pilot phase of a novel undergraduate elective (“stewards for future”, SFF) for medical students at the Saarland University, Germany, between 2021 and 2023. We focused on knowledge and attitudes relevant to AMS. To allow for full immersion, we applied case-based learning, problem-based learning, and peer teaching in a small group teaching format spanning 15 hours, including AMS ward rounds. We obtained students’ pre- and post-course self-assessment regarding AMS topics using 5-point Likert scales modified from the previously published ASSURE elective, as well as their subjective experience using the German short intrinsic motivation inventory.
Results: Over four terms, 23 undergraduate medical students from the clinical phase participated in the elective. Participants reported an increase in their ability to explain the concept of AMS (mean and standard deviation, pre 3.26±0.94 vs. post 4.74±0.44, p<0.0001), their confidence in choosing the appropriate antibiotic (pre 2.22±0.78 vs. post 3.57±0.58, p<0.0001), their ability to judge potential drug side effects (pre 2.09±0.72 vs. post 3.43±0.71, p<0.0001), their confidence in communicating with colleagues about antibiotics (pre 2.30±0.86 vs. post 3.52±0.83, p<0.0001), their understanding of diagnostics as an AMS tool (pre 4.22±0.41 vs. post 4.91±0.28, p<0.0001), and their ability to evaluate the roles of all AMS team members including their own (pre 2.52±0.77 vs. post 4.13±0.68, p<0.0001). Participants reported having enjoyed the course (4.6±0.5), while they were moderately satisfied with their performance (3.8±1.0). Pressure and anxiety levels were reported to be low (1.8±0.9 and 2.0±1.0 each).
Conclusions: Student participants of the elective SFF reported increased competencies relevant to AMS, while enjoying the course format. Sustainability and scalability will ultimately depend on the implementation into the core curriculum
The effect of Germany´s organised cancer screening guidline (oKFE-RL) for the prevention of cervical cancer
No full textDie vorliegende Arbeit untersucht den Effekt der im Jahr 2020 vom G-BA eingeführten oKFE-RL zur Prävention des Zervixkarzinoms. Diese sieht bei Frauen bis zum Alter von 34 Jahren eine jährliche zytologische Diagnostik vor. Für Frauen ab 35 Jahren wird eine Kombinationsuntersuchung eingeführt, die aus Zytologie und HPV-HR-Test (P-Ko-Test) besteht und alle drei Jahre erfolgt.
Unsere Daten von 2020–2022 bilden die erste Runde dieses neuen Screeningprogramms ab, das zunächst für einen Zeitraum von sechs Jahren geplant ist.
Der zusätzlich zur Zytologie eingeführte HPV-HR-Test erfordert eine Testung auf 13 definierte HPV-HR-Typen und bei positivem Befund eine Differenzierung der HPV-HR-Typen 16 und 18. Wir haben ein Testsystem eingesetzt, das eine erweiterte Genotypisierung ermöglicht und insgesamt 14 Genotypen erfasst, inklusive sechs Einzeltypen und drei Gruppen.
Aus den Laboratorien für Zytodiagnostik und Molekularbiologie der Praxen in Cölpin und Saarbrücken liegen für die erste vollständige Runde der oKFE-RL über den Zeitraum 2020–2022 Daten zu insgesamt 222.861 Präventionsuntersuchungen vor. Davon sind 128.272 Kombinationsuntersuchungen bei Frauen ab 35 Jahren.
Unsere Analyse ergab eine HPV-HR-Positivrate von 8,11 %. Der dominierende HPV-Typ ist HPV 16, gefolgt von HPV 56/59/66 und HPV 31.
Die Gesundheitsforen Leipzig, welche im Auftrag des G-BA eine begleitende Evaluation durchführen, geben für die Jahre 2021–2022 eine Positivrate von 8,56 % an. Diese Raten liegen eng beieinander, und wir können daher davon ausgehen, dass unsere Daten auch für ein größeres Kollektiv repräsentativ sind. Somit kann die Dokumentationslücke der Gesundheitsforen Leipzig für das dort fehlende Jahr 2020 geschlossen werden.
Ein stringenter altersabhängiger Abklärungsalgorithmus fordert bei auffälligen Befunden sowie persistierenden HPV-HR-Infektionen eine Abklärungskolposkopie und, falls indiziert, eine Biopsie mit histologischer Untersuchung.
Auf dieser Grundlage war es möglich, die epidemiologischen, zytologischen, virologischen und histologischen Befunde in diesen drei Jahren zu erfassen und miteinander zu korrelieren.
Im Vergleich zur Ausgangssituation im Jahre 2019 wurde bei Frauen ab 35 ein Anstieg der CIN 3-Läsionen um das Doppelte festgestellt.
Der Altersgipfel der Patientinnen mit einer CIN 3 verschob sich um 10 Jahre auf die Gruppe der Frauen zwischen dem 35. und 40. Lebensjahr.
Parallel dazu beobachteten wir einen deutlichen Rückgang der CIN 3- in der Altersklasse der Frauen unter 35 Jahren, speziell in der Gruppe der 20–29-jährigen, von denen fast 70 % eine HPV-Impfung erhalten hatten.
Die Altersstratifizierung der unterschiedlichen HPV-HR-Genotypen, sowohl unabhängig von der Morphologie als auch bei histologisch nachgewiesenen CIN 1-, CIN 2- und CIN 3-Läsionen, ermöglicht einen differenzierteren Einblick als bisher in die Interaktion von Morphologie und Virologie.
Die Inzidenz der Zervixkarzinome zeigte im Vergleich zu den Vorjahren keine Veränderung. Diese Entität muss aufgrund ihres biologischen Verhaltens über einen längeren Zeitraum beobachtet werden, bevor weitere Rückschlüsse gezogen werden können.
Die vorliegende Beobachtungsstudie wurde an einem größeren Kollektiv unter
real-world-Bedingungen durchgeführt. Die Robustheit unserer Daten und der Umfang unserer über drei Jahre dokumentierten Untersuchungsergebnisse erlauben belastbare Rückschlüsse auf die Prävalenz von verschiedenen HPV-HR-Typen bei Frauen ab 35 Jahren in Deutschland. Darüber hinaus können wir Aussagen treffen über die Verteilung der jeweiligen
HPV-HR-Typen in histologisch nachgewiesenen zervikalen intraepithelialen Neoplasien. Eine solche Differenzierung wird in dieser Größenordnung erstmalig in Deutschland gezeigt.
Mit der erweiterten Genotypisierung lässt sich auch das onkogene Potential der HPV-HR-Typen bei den einzelnen zervikalen intraepithelialen Neoplasien im Individualfall abschätzen. Hier sehen wir einen Ansatz zur Risikostratifizierung, um mit einem überarbeiteten Abklärungsalgorithmus zukünftig Überdiagnostik und Übertherapie zu vermeiden.This study investigates the effect of Germany`s organised cancer screening guideline (oKFE-RL) for the prevention of cervical cancer, introduced in 2020 by the Joint Federal Committee (G-BA). This guideline recommends annual cytological diagnostics for women up to the age of 34 and a combined examination, consisting of cytology and HPV testing (co-testing) every three years for women aged 35 and older.
Our data from 2020–2022 cover the first of two rounds of this new screening program, initially planned for a six-year period.
The HPV test, introduced in addition to cytology, requires testing for 13 defined high-risk HPV types and, in case of a positive result, a differentiation of HPV types 16 and 18. We used a testing system that enables extended genotyping and captures a total of 14 genotypes, including six individual types and three groups.
Data for the entire first round of the oKFE-RL, i. e. over the period 2020–2022, were collected in our laboratories for cytodiagnostics and molecular biology in Cölpin and Saarbrücken, covering a total of 222,861 preventive examinations. Of these, 128,272 were combined examinations conducted for women aged 35 and older.
Our analysis indicated an HPV positivity rate of 8.11%, with HPV 16 being the most prevalent type, followed by HPV 56/59/66 and HPV 31. The Gesundheitsforen Leipzig, which conducted an accompanying evaluation on behalf of the Joint Federal Committee (G-BA), report a positivity rate of 8.56% for the period 2021–2022. Our data are consistent with this result, suggesting that our sample can be considered representative of a larger cohort and may serve to bridge the 2020 documentation gap in the evaluation of the Gesundheitsforen Leipzig.
A stringent, age-dependent diagnostic algorithm mandates colposcopy for clinically relevant findings and persistent HPV infections, with a biopsy and histological examination performed when indicated. Based on this framework, we were able to collect and correlate epidemiological, cytological, virological, and histological findings over these three years.
An increase in CIN 3 lesions by a factor of two was observed in women aged 35 and older compared to the 2019 baseline, with the peak age shifting by ten years to the group of women aged 35–40.
Concurrently, a substantial decrease in CIN 3 lesions was observed in women under 35, particularly in those aged 20–29, of whom nearly 70% had received an HPV vaccination.
Age-stratified analysis of different HPV genotypes – in histologically confirmed CIN 1, CIN 2, and CIN 3 lesions or irrespective of morphology – provides a more nuanced understanding of the interaction between morphology and virology than previously available.
The incidence of cervical carcinomas remained unchanged compared to previous years. Due to their biological behavior, these entities must be observed over a longer period before further conclusions can be drawn.
This observational study was conducted on a large cohort under real-world conditions. The robustness of our data and the range and volume of our findings, documented over three years, allow valid conclusions about the prevalence of different HPV types in women aged 35 and older in Germany. Furthermore, we can provide insights into the distribution of respective HPV types in histologically confirmed cervical intraepithelial neoplasms. This level of differentiation is being shown for the first time in Germany at this scale.
Extended genotyping also allows for the assessment of the oncogenic potential of HPV types in individual cervical intraepithelial neoplasms. This may represent an approach for risk stratification, with the goal of preventing overdiagnosis and overtreatment through a refined diagnostic algorithm in the future
Identification and heterologous expression of an NRPS biosynthetic gene cluster responsible for the production of the pyrazinones Ichizinone A, B and C
Get PDFPyrazinones are a growing family of microbial NRPS-derived natural products showing interesting biological
activities. These compounds are characterized by the presence of either a di- or trisubstituted heterocyclic,
nonaromatic 2(1 H)-pyrazinone core in their structure. The most commonly occurring disubstituted pyrazinone
natural products are synthesized through a dipeptide intermediate, which is further cyclized to yield the pyrazinone
moiety. Trisubstituted pyrazinones are seldom found in natural products, with JBIR56 and JBIR57, isolated from
marine Streptomyces, being notable examples. In contrast to the simply organized disubstituted pyrazinones, JBIR56
and JBIR57 are syn-thesized as tetrapeptides with unnatural beta-amino acid residue involved in the for-mation
of the pyrazinone moiety. Despite interesting structural features, biosynthetic routes leading to the production of
these compounds have not been reported yet. Here we report the discovery of new members of trisubstituted
pyrazinone family– tetrapeptides ichizinones A-C in Streptomyces sp. LV45-129. Through sequence analysis and
heterologous expression, a biosynthetic gene cluster encoding ichizinone production was identified. Based on
gene annotation and sequence homology, a biosynthetic model was suggested. The presented results provide
insights into the biosynthesis of rare trisubstituted pyrazinone natural products
Hf6Al7 and Hf4.44(1)Nb1.56(1)Al7—the First Fully Ordered Main Group Metal Containing W6Fe7 Type Compound and its Ternary Coloring Variant
Get PDFAttempts to synthesize Hf4NbAl7 led to the discovery of nominal Hf4Nb2Al7 instead of the envisioned product. It was identified based on powder diffraction data. The compound can be described as a substitutional/coloring variant of the rhombohedral W6Fe7 type structure (space group Rmathematical equationm). The formation of the ternary compound motivates the synthesis of the binary compound Hf6Al7. Different synthetic strategies lead to its discovery. The crystal structures of the binary as well as its ternary coloring variant are refined from single-crystal X-ray diffraction data showing both the same obverse–reverse twinning. For the Nb-containing phase, a composition of Hf4.44(1)Nb1.56(1)Al7 is refined, in agreement with the powder X-ray data. Solid-state 27Al NMR investigations indicate the formation of a crystalline compound; however, only one distinct signal can be observed in contrast to the two crystallographic Al positions. Magnetic susceptibility measurements confirm the expected Pauli-paramagnetic character. Quantum-chemical calculations alongside analyses of the chemical bonding with the LOBSTER program package show that a strong Hf–Hf interaction is present, which transforms into an even stronger Nb–Nb interaction in nominal Hf4Nb2Al7. For the latter, three substitutional variants are calculated, clearly indicating the experimentally observed one as the most stable