Otto-von-Guericke-Universität Magdeburg
  • Magdeburg, Saxony-Anhalt, Germany
Recent publications
Lascoux polynomials have been recently introduced to prove polynomiality of the maximum-likelihood degree of linear concentration models. We find the leading coefficient of the Lascoux polynomials (type C) and their generalizations to the case of general matrices (type A) and skew symmetric matrices (type D). In particular, we determine the degrees of such polynomials. As an application, we find the degree of the polynomial δ(m,n,n−s) of the algebraic degree of semidefinite programming, and when s=1 we find its leading coefficient for types C, A and D.
The involvement of highly chemically reactive H2 greatly increases the fuel explosion risk. In order to reveal the elevated explosion risk of LPG/DME blended gas due to the participation of H2, the explosion-promoting dynamics of H2 and its sensitivity characteristics are investigated based on a combination method of numerical simulation, experimental verification and theoretical analysis. The results show that the participation of H2 increases the explosion overpressure and the shockwave propagation velocity by 147.9% and 90% respectively to the greatest extent. The explosion temperature shows five typical combustion stages, with the participation of H2, the maximum temperature rise range of the shock wave adiabatic compression heating period and the combustion period is significantly increased, the adiabatic holding time is prolonged, the peak flame temperature is increased, and the flame propagation velocity is also significantly improved. The addition of H2 causes the relative distance between the explosion shock wave and the flame front first increases, then decreases and then increases in the shape of “half-morning glory”. The number and sensitivity coefficients of the new explosion-promoting elementary reactions brought by H2 are larger than that of the new explosion-inhibiting elementary reactions, which explains and confirms the explosion-promoting nature of H2 in terms of the reaction mechanism.
In this paper, we consider further applications of (n,m)-functions for the construction of 2-designs. For instance, we provide a new application of the extended Assmus-Mattson theorem, by showing that linear codes of certain APN functions with the classical Walsh spectrum support 2-designs. With this result, we give several sufficient conditions for an APN function with the classical Walsh spectrum to be CCZ-inequivalent to a quadratic one. On the other hand, we use linear codes and combinatorial designs in order to study important properties of (n,m)-functions. In particular, we provide a characterization of a quadratic Boolean bent function by means of the 2-transitivity of its automorphism group. Finally, we give a new design-theoretic characterization of (n,m)-plateaued and (n,m)-bent functions and provide a coding-theoretic as well as a design-theoretic interpretation of the extendability problem for (n,m)-bent functions.
Lignocellulose is one of the most promising renewable bioresources for the production of chemicals. For sustainable and competitive biorefineries, effective valorization of all biomass fractions is crucial. However, current efforts in lignocellulose fractionation are limited by the use of either toxic or suboptimal solvents that do not always allow producing clean and homogeneous streams. Here, we present a computational screening approach that covers more than 8000 solvent candidates for the processing of lignocellulosic biomass. The automated screening identified highly effective, non-intuitive solvents based on physico-chemical properties, solubilities of the biomass fractions, and environmental, health and safety properties. Solubility experiments for the lignin and cellulose fraction confirmed the applicability of the proposed framework in biomass processing. In addition to the traditional “lignin-first” approaches, we identified solvents applicable for the complete dissolution of biomass. Furthermore, we elucidated particular structural patterns in solvents featuring high lignin solubility. The most promising solvents attained lignin solubilities of more than 33 wt%.
Flow-induced vibration (FIV) is a common phenomenon observed in internal flows and is frequently encountered in technical systems like process plants, nuclear plants, oil-piping or heat exchangers. Compared to single-phase flows, FIV is more difficult to predict and analyze for internal two-phase flows. As a result, experimental data and analysis tools related to two-phase flow are limited to specific aspects or conditions. Another problem is that for real-world applications, FIV analysis is applied to multi-structural components, which becomes complicated due to the size of the technical systems. Thus, experimental studies are usually realized first within the laboratory using a prototype of the original structure. Besides experimental investigations, Computational Fluid Dynamics (CFD) is increasingly adopted and already a prevalent tool for FIV assessment. However, further development in CFD models and methods is necessary in order to complement the experimental database. Additionally, CFD is useful for enhanced understanding of fundamental aspects of two-phase flows, and for gaining insights from situations where experiments are difficult or infeasible, such as in deep-sea bore-wells, sub-sea riser pipelines, and in nuclear installations. It is also known that there is a lack of sufficiently accurate empirical correlations for terms related to mass, momentum, and energy transfer across the phases for two-phase flows, and CFD can be useful in this respect. Furthermore, for estimating the accuracy of CFD models, comparisons with benchmark results for two-phase, internal, multi-structural flows are necessary. Unfortunately, the experimental database involving internal two-phase flows is very limited, and this is a bottleneck for the development of computational techniques. The following contribution presents a review of the research on FIV involving two-phase internal flows with relevance to multi-structural components. Methodological literature for two-phase flow measurements along with the latest applications are put forth. Problem areas of two-phase FIV systems have been brought out, and future avenues of research for two-phase, internal FIV are identified. The following specific areas of two-phase FIV are reviewed. Two-phase FIV in subsea risers and in pipeline riser systems is discussed. The slug flow regime is analyzed in particular due its predominant impact on two-phase FIV. Parameters affecting two-phase FIV along with two-phase correlations are discussed. Power Spectrum Density (PSD) and Fourier transform applications for two-phase FIV form another section. Latest research efforts involving the two-way interaction of fluid and structure are presented. Both numerical and experimental works have been reviewed. The bulk of the important works for two-phase FIV is experimental in nature. Numerical models and computational power have not been developed enough for simulating more complex, multistructural flows. They are limited to simple cases involving simplified computational models. Experimental efforts for large multistructural components involve the initial use of prototypes and can prove to be costly for fully developed industrial-scale rigs. However, experimentation currently holds an irreplaceable position in two-phase FIV studies.
Microbiota research has received an increasing attention for its role in disease development and fungi are considered as one of the key players in the microbial niche. Various sequencing approaches have been applied to uncover the role of fungal community in health and disease; however, little is known on the performance of various primers and comparability between the studies. Motivated by the recent publications, we performed a systematic comparison of the 18S and ITS regions to identify the impact of various primers on the sequencing results. Using four pairs of primers extensively used in literature, fungal community was retrieve from 25 fecal samples, and applying high throughput sequencing; and the results were compared in order to select the most suitable primers for fungal detection in human fecal samples. Considering the high variability between samples, primers described in the Earth microbiome project detected the broadest fungal spectrum suggesting its superior performance in mycobiome research.
Background The aim of this study was to explore the relationship between follow-up imaging characteristics and overall survival (OS) in advanced hepatocellular carcinoma (HCC) patients under sorafenib treatment. Methods Associations between OS and objective response (OR) by mRECIST or early tumor shrinkage (ETS; ≥20% reduction in enhancing tumor diameter at the first follow-up imaging) were analyzed in HCC patients treated with sorafenib within a multicenter phase II trial (SORAMIC). 115 patients were included in this substudy. The relationship between survival and OR or ETS were explored. Landmark analyses were performed according to OR at fixed time points. Cox proportional hazards models with OR and ETS as a time-dependent covariate were used to compare survival with factors known to influence OS. Results The OR rate was 29.5%. Responders had significantly better OS than non-responders (median 30.3 vs. 11.4 months; HR, 0.38 [95% CI, 0.22–0.63], p < 0.001), and longer progression-free survival (PFS; median 10.1 vs. 4.3 months, p = 0.015). Patients with ETS ≥ 20% had longer OS (median 22.1 vs. 11.4 months, p = 0.002) and PFS (median 8.0 vs. 4.3 months, p = 0.034) than patients with ETS < 20%. Besides OR and ETS, male gender, lower bilirubin and ALBI grade were associated with improved OS in univariate analysis. Separate models of multivariable analysis confirmed OR and ETS as independent predictors of OS. Conclusion OR according to mRECIST and ETS in patients receiving sorafenib treatment are independent prognostic factors for OS. These parameters can be used for assessment of treatment benefit and optimal treatment sequencing in patients with advanced HCC.
Background Parkinson’s disease (PD) is a progressive, neurodegenerative disorder. In the advanced stages it can result in severe disability despite optimal treatment. Data suggests heterogeneous classification of PD stages among physicians in different countries. The purpose of the OBSERVE-PD study was to evaluate the proportion of patients with advanced PD (APD) according to physicians’ judgments in an international cohort. Methods A cross-sectional, observational study was conducted in 18 countries. Data were collected during a single patient visit. Demographic data, disease status, current medical treatment, and quality of life were evaluated for the German cohort and compared to the international cohort. Potential prognostic factors of physicians’ classification of APD in the German and international cohorts were identified using logistic regression. Results In total, 177 German and 2438 international patients were enrolled. 68.9% of the German and 50.0% of the international patients were classified by physicians as APD. Despite similar demographics and comparable disease severity, motor fluctuations (odds ratio [OR], 49.7; 95% confidence interval [CI], 8.5–291.9) and current device-aided treatment (OR 8.7; CI 5.5–13.8) showed the strongest association to physicians’ classification of APD in the German and the international cohorts, respectively. The number of different oral anti-Parkinson-medications showed opposed associations with APD-classification between the international (OR 1.19; CI 1.03–1.37) and German (OR 0.46; CI 0.18–1.18) cohort. Although 58.2% of the German patients diagnosed with APD were considered eligible for device-aided treatment, only 40.8% actually received it. Conclusions This study highlights the challenges in the recognition and the effective management of APD in Germany and emphasizes the necessity of complying with standard diagnostic criteria for identification of patients with APD. Therapeutic approaches differed internationally, with a tendency in Germany towards a more complex oral medication regimen for patients with APD. In view of similar quality of life and disease status in both cohorts, our findings may prompt further exploration of parameters for disease classifications, and consideration of optimal treatment strategies.
Background Pain occurs in the majority of patients with late onset Pompe disease (LOPD) and is associated with a reduced quality of life. The aim of this study was to analyse the pain characteristics and its relation to a small nerve fiber involvement in LOPD patients. Methods In 35 patients with LOPD under enzyme replacement therapy without clinical signs of polyneuropathy (19 females; 51 ± 15 years), pain characteristics as well as depressive and anxiety symptoms were assessed using the PainDetect questionnaire (PDQ) and the hospital anxiety and depression scale (HADS), respectively. Distal skin biopsies were analysed for intraepidermal nerve fiber density (IENFD) and compared to age- and gender-matched reference data. Skin biopsies from 20 healthy subjects served as controls to assure validity of the morphometric analysis. Results Pain was reported in 69% of the patients with an average intensity of 4.1 ± 1.1 on the numeric rating scale (NRS; anchors: 0–10). According to PDQ, neuropathic pain was likely in one patient, possible in 29%, and unlikely in 67%. Relevant depression and anxiety symptoms occurred in 31% and 23%, respectively, and correlated with pain intensity. Distal IENFD (3.98 ± 1.95 fibers/mm) was reduced in 57% of the patients. The degree of IENFD reduction did not correlate with the durations of symptoms to ERT or duration of ERT to biopsy. Conclusions Pain is a frequent symptom in treated LOPD on ERT, though a screening questionnaire seldom indicated neuropathic pain. The high frequency of small nerve fiber pathology in a treated LOPD cohort was found regardless of the presence of pain or comorbid risk factors for SFN and needs further exploration in terms of clinical context, exact mechanisms and when developing novel therapeutic options for LOPD.
Background Intermittent hypoxia applied at rest or in combination with exercise promotes multiple beneficial adaptations with regard to performance and health in humans. It was hypothesized that replacing normoxia by moderate hyperoxia can increase the adaptive response to the intermittent hypoxic stimulus. Objective Our objective was to systematically review the current state of the literature on the effects of chronic intermittent hypoxia–hyperoxia (IHH) on performance- and health-related outcomes in humans. Methods PubMed, Web of Science™, Scopus, and Cochrane Library databases were searched in accordance with PRISMA guidelines (January 2000 to September 2021) using the following inclusion criteria: (1) original research articles involving humans, (2) investigation of the chronic effect of IHH, (3) inclusion of a control group being not exposed to IHH, and (4) articles published in peer-reviewed journals written in English. Results Of 1085 articles initially found, eight studies were included. IHH was solely performed at rest in different populations including geriatric patients ( n = 1), older patients with cardiovascular ( n = 3) and metabolic disease ( n = 2) or cognitive impairment ( n = 1), and young athletes with overtraining syndrome ( n = 1). The included studies confirmed the beneficial effects of chronic exposure to IHH, showing improvements in exercise tolerance, peak oxygen uptake, and global cognitive functions, as well as lowered blood glucose levels. A trend was discernible that chronic exposure to IHH can trigger a reduction in systolic and diastolic blood pressure. The evidence of whether IHH exerts beneficial effects on blood lipid levels and haematological parameters is currently inconclusive. A meta-analysis was not possible because the reviewed studies had a considerable heterogeneity concerning the investigated populations and outcome parameters. Conclusion Based on the published literature, it can be suggested that chronic exposure to IHH might be a promising non-pharmacological intervention strategy for improving peak oxygen consumption, exercise tolerance, and cognitive performance as well as reducing blood glucose levels, and systolic and diastolic blood pressure in older patients with cardiovascular and metabolic diseases or cognitive impairment. However, further randomized controlled trials with adequate sample sizes are needed to confirm and extend the evidence. This systematic review was registered on the international prospective register of systematic reviews (PROSPERO-ID: CRD42021281248) ( https://www.crd.york.ac.uk/prospero/ ).
Virtual reality is increasingly applied to support physical training and improve athletes’ performance in sports. Nevertheless, there is a research deficit in that, especially in martial arts, it has not yet been shown to what extent the response behavior of athletes in virtual reality is the same as in the real world. If this can be confirmed, a transfer of VR-adapted skills to RW can be expected and sports training in a virtual environment can be applied to improve sports performance. Since the response behavior is essential for many sports, this study compares it in karate kumite to the competition-important attack (Kizami-Zuki) of a real and a virtual opponent. Experienced karate athletes wore a head-mounted display and were asked to respond quickly and efficiently to 22 karate attacks, of which eight were Kizami Zuki’s attacks. Using a video-based movement assessment, karate experts quantified the response behavior with the parameters ‘time for response’, ‘response quality’ and ‘kind of response’. Results show no significant differences in ‘time for response’ and ‘kind of response’ between both conditions (virtual reality vs. real world). Only the ‘response quality’ was rated better in real world than in virtual reality. It is concluded that the ‘time of response’ and ‘kind of response’ for karate kumite athletes in virtual reality are similar to that in the real world.
Background Achondroplasia is the most common form of skeletal dysplasia, with serious comorbidities and complications that may occur from early infancy to adulthood, requiring lifelong management from a multidisciplinary team expert in the condition The European Achondroplasia Forum guiding principles of management highlight the importance of accurate diagnosis and timely referral to a centre specialised in the management of achondroplasia to fully support individuals with achondroplasia and their families, and to appropriately plan management. The European Achondroplasia Forum undertook an exploratory audit of its Steering Committee to ascertain the current situation in Europe and to understand the potential barriers to timely diagnosis and referral. Results Diagnosis of achondroplasia was primarily confirmed prenatally (66.6%), at Day 0 (12.8%) or within one month after birth (12.8%). For suspected and confirmed cases of achondroplasia, a greater proportion were identified earlier in the prenatal period (87.1%) with fewer diagnoses at Day 0 (5.1%) or within the first month of life (2.6%). Referral to a specialist centre took place after birth (86.6%), predominantly within the first month, although there was a wide variety in the timepoint of referral between countries and in the time lapsed between suspicion or confirmed diagnosis of achondroplasia and referral to a specialist centre. Conclusions The European Achondroplasia Forum guiding principles of management recommend diagnosis of achondroplasia as early as possible. If concerns are raised at routine ultrasound, second line investigation should be implemented so that the diagnosis can be reached as soon as possible for ongoing management. Clinical and radiological examination supported by molecular testing is the most effective way to confirm diagnosis of achondroplasia after birth. Referral to a centre specialised in achondroplasia care should be made as soon as possible on suspicion or confirmation of diagnosis. In countries or regions where there are no official skeletal dysplasia reference or specialist centres, priority should be given to their creation or recognition, together with incentives to improve the structure of the existing multidisciplinary team managing achondroplasia. The length of delay between diagnosis of achondroplasia and referral to a specialist centre warrants further research.
Supercritical water gasification is a promising technology in the context of carbon neutrality, since it converts coal into hydrogen and easily-captured CO2. A fully resolved direct numerical simulation of single particle gasification in supercritical water is conducted in this paper in order to investigate process details at particle scale. To handle the shrinking reactive particle, a directional ghost-cell immersed boundary method is used with a general Robin-type boundary condition at the interface. Detailed flow field and interphase heat/mass transfer near the reactive coal particle are revealed and compared with standard non-reactive cases-used for validation. They are found to be significantly affected by the combined effect of the reaction-induced Stefan flow, particle shrinking, species generation or destruction, and reaction heat release. The chemical processes are then studied with special attention on the gas-phase reaction timescale. This study delivers a detailed understanding of coal particle gasification in supercritical water, and provides a first successful test of efficient numerical methods needed for large-scale supercritical water gasification simulations.
Thermodynamic modelling is an effective approach to accelerate the development of novel materials such as V-based alloys. In the present work, the results of thermodynamic modelling of the ternary system V–Ti–B using the “CALculation of PHAse Diagrams” (CALPHAD) method are presented. The thermodynamic descriptions of the binary systems V–Ti, V–B, and Ti–B are based on available publications whereas thermodynamic parameters for the ternary system stem from the iterative approximation to the experimental investigations, which further serve for verifying the calculated phase diagram. Thus, eight different alloys in the compositional range of 10–40 at.% Ti and B were analyzed aiming at identifying the evolving phases. A set of thermodynamic parameters is proposed. The calculated isothermal phase diagram at 1673 K exhibits a high degree of agreement with the literature and experimental observations. In our further work, the thermodynamic data generated in this study will be useful to develop the quaternary V–Ti–Si–B system.
The present study reports on the existence of a new ternary phase, V8SiB4, in the V–Si–B system. The new phase was found in alloys heat-treated at 1400 °C for 100 h and 200 h within the Vss–V3Si–V5SiB2 phase field at 1600 °C. The crystal structure of V8SiB4 was determined by combining energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and density functional theory (DFT) calculations. To further examine the stability of V8SiB4, electronic density-of-states (EDOS), phononic density-of-states (PDOS), the chemical bonding and the elastic properties of V8SiB4 were calculated using DFT and compared with the properties of V5SiB2 (T2).
Nirmatrelvir is an antiviral agent active against SARS-CoV-2, the virus causing the pandemic disease COVID-19. It is administrated in combination with the protease inhibitor ritonavir, which acts in case of COVID-19 mainly as enzyme blocking agent preventing the premature metabolic elimination of nirmatrelvir. The combination of the two drugs in separate tablets is marketed under the brand name Paxlovid® and shows good effectivity in preventing the progression of COVID-19 to severe disease state. In this work, we described a LC-MS/MS method for the simultaneous quantification of nirmatrelvir and ritonavir in human plasma of patients treated for COVID-19 with Paxlovid®. After addition of D6-ritonavir as internal standard, plasma proteins were precipitated by the addition of methanol. The analytes were separated by gradient elution on a C18-column and were detected by tandem mass spectrometry. Calibration functions were linear in the ranges of 10 – 10000 ng/mL for nirmatrelvir and 2 – 2000 ng/mL for ritonavir. Inter-day and intra-day precision and accuracy was better than 15 % in the quality control samples and better than 20 % at the LLOQ. The method was successfully applied on samples of hospitalized patients treated for COVID-19 and proved to be capable in supporting therapeutic drug monitoring (TDM).
In carrier-based Dry Powder Inhalers (DPI), fine API powder covers the surface of bigger carrier particles giving rise to dry coated particles, such that their flow properties are improved. In the hard-shell capsule of Cyclohaler DPI, powder deaggregation and discharge occurs as a result of the centrifugal motion and the subsequent aerodispersion to the mouthpiece induced by the patient’s inhalation. In this work, the crucial initial transient of this dispersion process was analysed through DEM (Discrete Element Method) simulations, by considering the solid phase only. The accelerated rotational motion of the capsule was simulated in the frame of reference of an observer rotating with the capsule, appropriately considering fictitious forces. The effect of the vibrations due to collisions between the capsule and the inhaler on powder discharge was evaluated as well for carrier particle systems. The results provide a punctual mapping of the particle-wall collisions within the capsule, allowing the path of the solids to be tracked until discharge. Simulations were carried out on drug-carrier blends with extreme size difference, considering adhesive interactions, elucidating the early-stage dynamics of the detachment process that occurs inside the capsule due to the interactions between particles and between particles and walls.
Antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) comprises a group of multisystem disorders involving severe, systemic, small-vessel vasculitis with short- and long term serious and life-threating complications. Despite the simplification of treatment, fundamental aspects concerning assessment of its efficacy and its adaptation to encountered complications or to the relapsing/remitting/subclinical disease course remain still unknown. The pathogenesis of AAV is complex and unique, and despite the progress achieved in the last years, much has not to be learnt. Foremost, there is still no accurate marker enabling us to monitoring disease and guide therapy. Therefore, the disease management relays often on clinical judgment and follows a” trial and error approach”. In the recent years, an increasing number of new molecules s have been explored and used for this purpose including genomics, B- and T-cell subpopulations, complement system factors, cytokines, metabolomics, biospectroscopy and components of our microbiome. The aim of this review is to discuss both the role of known historical and clinically established biomarkers of AAV, as well as to highlight potential new ones, which could be used for timely diagnosis and monitoring of this devastating disease, with the goal to improve the effectiveness and ameliorate the complications of its demanding therapy.
Contrast-induced encephalopathy (CIE) is a rare complication of coronary and neurointerventional procedures. The condition is believed to arise from endothelial damage secondary to exposure to iodinated contrast media. A wide spectrum of clinical manifestations has been reported including seizures, cortical blindness, and focal neurological deficits. This report details the case of fully reversible CIE mimicking severe anterior circulation stroke in a 55-year-old female following elective endovascular treatment with a flow diverter of a carotid cave aneurysm. The patient was managed conservatively with intravenous hydration and steroids and showed an excellent prognosis with supportive management.
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7,923 members
Konrad Mühler
  • Department of Simulation and Graphics (ISG)
Frank Ortmeier
  • Faculty of Computer Science
Christian Apfelbacher
  • Institute of Social Medicine and Health Systems Research
Alexander Hohn
  • Clinic for Radiology and Nuclear Medicine
Oliver Stork
  • Department of Genetics & Molecular Neurobiology
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Universitätsplatz 2, 39106, Magdeburg, Saxony-Anhalt, Germany
Head of institution
Jens Strackeljan
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http://www.ovgu.de/
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+49 391 67-01
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