Technische Universität Dresden: Qucosa
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Surfactant administration during endotracheal CPAP
No full textAim:
Whereas there is agreement that surfactant should be administered without mechanical ventilation, there is still a debate concerning the optimal method. DD-SURF combines the benefits of INSURE and less invasive surfactant administration (LISA). The efficacy of this approach has not been evaluated yet.
Methods:
Retrospective cohort study of all preterm newborns below 300/7 weeks gestational age admitted to the neonatal intensive care unit. Data on surfactant therapy, respiratory support during the first 96 h of life and neonatal morbidities until hospital discharge were collected from the electronic patient charts to evaluate the efficacy and safety of our approach.
Results: In total, 222 newborns met the inclusion criteria; 174 (78%) received surfactant in the delivery room by the DD-SURF procedure and 21 infants (10%) were not extubated after surfactant administration (Surf-and-vent group). After DD-SURF, 75% of patients did not require reintubation. Intraventricular haemorrhage and bronchopulmonary dysplasia occured more often in infants after DD-SURF failure than after successful DD-SURF.
Conclusion:
DD-SURF potentially combines the benefits of INSURE and LISA and represents a useful alternative of surfactant delivery with comparable success rates to thin-catheter surfactant administration
Unraveling the infuence of trial‑based motivational changes on performance monitoring stages in a fanker task
No full textPerformance monitoring (PM) is a vital component of adaptive behavior and known to be influenced by motivation. We examined effects of potential gain (PG) and loss avoidance (LA) on neural correlates of PM at different processing stages, using a task with trial-based changes in these motivational contexts. Findings suggest more attention is allocated to the PG context, with higher amplitudes for respective correlates of stimulus and feedback processing. The PG context favored rapid responses, while the LA context emphasized accurate responses. Lower response thresholds in the PG context after correct responses derived from a drift–diffusion model also indicate a more approach-oriented response style in the PG context. This cognitive shift is mirrored in neural correlates: negative feedback in the PG context elicited a higher feedback-related negativity (FRN) and higher theta power, whereas positive feedback in the LA context elicited higher P3a and P3b amplitudes, as well as higher theta power. There was no effect of motivational context on response-locked brain activity. Given the similar frequency of negative feedback in both contexts, the elevated FRN and theta power in PG trials cannot be attributed to variations in reward prediction error. The observed variations in the FRN indicate that the effect of outcome valence is modulated by motivational salience
COMPASS: deCOMPressing stomA and two-Stage elective resection vs. emergency reSection in patients with left-sided obstructive colon cancer
No full textBackground
Colorectal cancer stands as a prevalent cause of cancer-related mortality, necessitating effective treatment strategies. Acute colonic obstruction occurs in approximately 20% of patients and represents a surgical emergency with substantial morbidity and mortality. The optimal approach for managing left-sided colon cancer with acute colonic obstruction remains debatable, with no consensus on whether emergency resection or bridge-to-surgery, involving initial decompressing stoma and subsequent elective resection after recovery, should be employed. Current studies show a decrease in morbidity and short-term mortality for the bridge-to-surgery approach, yet it remains unclear if the long-term oncological outcome is equivalent to emergency resection.
Methods
This prospective, randomized, multicenter trial aims to investigate the management of obstructive left-sided colon cancer in a comprehensive manner. The study will be conducted across 26 university hospitals and 40 academic hospitals in Germany. A total of 468 patients will be enrolled, providing a cohort of 420 evaluable patients, with an equal distribution of 210 patients in each treatment arm. Patients with left-sided colon cancer, defined as cancer between the left splenic flexure and > 12 cm ab ano and obstruction confirmed by X-ray or CT scan, are eligible. Randomization will be performed in a 1:1 ratio, assigning patients either to the oncological emergency resection group or the bridge-to-surgery group, wherein patients will undergo diverting stoma and subsequent elective oncological resection after recovery. The primary endpoint of this trial will be 120-day mortality, allowing for consideration of the time interval between diverting stoma and resection.
Discussion
The findings derived from this trial possess the potential to reshape the current clinical approach of emergency resection for obstructive left-sided colon cancer by favoring the bridge-to-surgery practice, provided that a reduction in morbidity can be achieved without compromising the oncological long-term outcome
In vivo microstructural investigation of the human tympanic membrane by endoscopic polarization-sensitive optical coherence tomography
No full textSignificance: Endoscopic optical coherence tomography (OCT) is of growing interest for in vivo diagnostics of the tympanic membrane (TM) and the middle ear but generally lacks a tissue-specific contrast. -
Aim: To assess the collagen fiber layer within the in vivo TM, an endoscopic imaging method utilizing the polarization changes induced by the birefringent connective tissue was developed. - Approach: An endoscopic swept-source OCT setup was redesigned and extended by a polarization-diverse balanced detection unit. Polarization-sensitive OCT (PS-OCT) data were visualized by a differential Stokes-based processing and the derived local retardation. The left and right ears of a healthy volunteer were examined. - Results: Distinct retardation signals in the annulus region of the TM and near the umbo revealed the layered structure of the TM. Due to the TM’s conical shape and orientation in the ear canal, high incident angles onto the TM’s surface, and low thicknesses compared to the axial resolution limit of the system, other regions of the TM were more difficult to evaluate. - Conclusions: The use of endoscopic PS-OCT is feasible to differentiate birefringent and nonbirefringent tissue of the human TM in vivo. Further investigations on healthy as well as pathologically altered TMs are required to validate the diagnostic potential of this technique
Synthese und photophysikalische Eigenschaften monometallischer C^C* Platin(II)-Formamidinatkomplexe mit sterisch anspruchsvollen Liganden
No full textEine neuartige – bisher als unzugänglich angesehene – Klasse von zyklometallierten Platin(II)-Komplexen wurde durch eine verbesserte Syntheseroute unter Verwendung von Liganden, die durch Dichtefunktionaltheorieberechnungen vorhergesagt wurden, hergestellt. Basierend auf einem gezielten quantenchemischen Screening wurden drei Modellliganden mit unterschiedlichem sterischem Anspruch ausgewählt und eine Serie von sechs photolumineszenten Platin(II)-Formamidinatkomplexen mit C^C* zyklometallierten Liganden hergestellt. Der Ligand mit dem geringsten sterischen Anspruch führte zu einem bimetallischen Komplex in zwei isomeren Formen, die voneinander getrennt und durch die entsprechenden Kristallstrukturen bestätigt werden konnten. Wie durch die quantenchemischen Rechnungen vorhergesagt, lieferten die sterisch stärker gehinderten Amidinatliganden die monometallischen Komplexe. Aufgrund des Verlusts der Metall-Metall-Wechselwirkungen zeigen diese Komplexe eine signifikante hypsochrome Verschiebung der Emissionswellenlänge. In Abhängigkeit vom zyklometallierten Ligand zeigt diese neue Klasse von Platin(II)-Emittern grün-blaue bis rein blaue Phosphoreszenz mit Quantenausbeuten von bis zu 87 % und kurzen Abklingzeiten
Synthesis and Photophysical Properties of Monometallic C^C* Platinum(II) Formamidinate Complexes using Sterically Demanding Ligands
No full textA novel class of cyclometalated platinum(II) complexes—previously considered to be inaccessible—was synthesized by an improved synthetic route utilizing ligands predicted by density functional theory calculations. Based on a concise quantum chemical screening three model ligands with varying steric demand were chosen and a series of six photoluminescent C^C* cyclometalated platinum(II) formamidinate complexes was obtained. The least sterically demanding ligand led to a bimetallic complex in two isomeric forms, which could be separated and confirmed by the corresponding solid-state structures. Sterically more hindered amidinate ligands gave the monometallic complexes supporting the theoretical predictions. The monometallic complexes show a significant hypsochromic shift of the emission wavelength, explained by the loss of the metal-metal interactions. Depending on the cyclometalating ligand quantum yields up to 87 % with short decay times were found for this new class of phosphorescent green-blue to pure blue platinum(II) emitters
VISTA Ligation Reduces Antitumor T-Cell Activity in Pancreatic Cancer
No full textImmunotherapy has shown promising results in multiple solid tumors and hematological malignancies. However, pancreatic ductal adenocarcinoma (PDAC) has been largely refractory to current clinical immunotherapies. The V-domain Ig suppressor of T-cell activation (VISTA) inhibits T-cell effector function and maintains peripheral tolerance. Here, we determine VISTA expression in nontumorous pancreatic (n = 5) and PDAC tissue using immunohistochemistry (n = 76) and multiplex immunofluorescence staining (n = 67). Additionally, VISTA expression on tumor-infiltrating immune cells and matched blood samples (n = 13) was measured with multicolor flow cytometry. Further, the effect of recombinant VISTA on T-cell activation was investigated in vitro, and VISTA blockade was tested in an orthotopic PDAC mouse model in vivo. PDAC showed significantly higher VISTA expression compared to that of a nontumorous pancreas. Patients with a high density of VISTA-expressing tumor cells had reduced overall survival. The VISTA expression of CD4+ and CD8+ T cells was increased after stimulation and particularly after a coculture with tumor cells. We detected a higher level of proinflammatory cytokine (TNFα and IFNγ) expression by CD4+ and CD8+ T cells, which was reversed with the addition of recombinant VISTA. A VISTA blockade reduced tumor weights in vivo. The VISTA expression of tumor cells has clinical relevance, and its blockade may be a promising immunotherapeutic strategy for PDAC
Modeling electrochemical processes in liquid metal batteries with a focus on mass transfer in molten salt electrolytes
No full textElectrical energy storage devices are necessary to meet the world’s increasing energy demand, while transitioning to intermittently available renewable energies. Liquid metal batteries are a promising technology in that field. They can be classified into two different cell types and multiple material pairings for their electrodes are possible. First, there are concentration cells, where batteries based on lithium and bismuth are a maturely developed representative. Second, there are displacement cells, which are currently developed with sodium and zinc as electrode materials. Despite having different working principles, they both consist of molten metal electrodes with a molten salt electrolyte in between, stably layered and self-segregating due to their density differences. Na-Zn displacement cells can employ a porous separator within the electrolyte layer. Furthermore, they are a favorable storage option due to their high theoretical cell potential, readily abundant materials and cost-advantages. Hence, investigations are here targeted at this type of liquid metal battery.
Multi-physical and multi-dimensional considerations are necessary to investigate liquid metal batteries, making this a highly complex matter and numerical modeling as well as experimental research are nontrivial. Even though, concentration cells have widely been investigated in recent years, the findings from these studies are not entirely transferable to Na-Zn cells. Moreover, they face the problem of mass transfer-induced self-discharge, which makes it necessary to understand fluid dynamics in the whole cell, and especially in the electrolyte. A diaphragm has often been proposed to reduce self-discharge – which is caused by transport of electroactive species – without demonstrating its efficacy and exact influence. Unfortunately, this conflicts with concentration gradients that largely influence cell efficiency, which are only reduced if the respective cell areas are set into motion.
Focusing on the liquid metal batteries’ electrolyte, species transport in the stagnant electrolytes of Li-Bi cells is investigated first. At the same time, a cell voltage model for Li-Bi liquid metal batteries is developed. This is followed by an assessment on flow phenomena likely to occur in Na-Zn batteries, where solutal convection, swirling flow, electrocapillary Marangoni convection and droplet formation are shown to be of most significance. Detailed investigations on solutal convection are conducted. In so doing, the diaphragm’s influence on solutal based self-discharge is studied.
Using the finite-volume method within the OpenFOAM framework, a numerical solver is established. Besides including the cell voltage model, which considers interface reactions in the electrochemical double layer, the solver is able to account for species transfer due to migration, diffusion and advection in the electrolyte as well as in the cathode. Furthermore, it is possible ito address the influence of porous media.
Besides having revealed that mass transport and concentration gradients have a significant effect on cell performance, it is confirmed that there must be flow in the electrolyte. In terms of solutal convection, resulting from unstable density gradients, a charge-discharge asymmetry during cycling is identified: convective flow is always present in one electrolyte compartment while the other compartment is stably stratified. However, phenomena during cell cycling depend largely on the previous cycles. Despite experiencing flow, minor areas of the electrolyte are still stably layered and cannot be disrupted by the gentle solutal flow. Furthermore, the importance of a flow barrier to reduce self-discharge is demonstrated. Nevertheless, such a barrier is not able to fully mitigate self-discharge, as species transport via migration and diffusion are still possible. Consequently, an optimization of operational current density, charging time and diaphragm properties are necessary to limit self-discharge and improve the performance of Na-Zn liquid metal batteries
Blasenbildung aufgrund von Übersättigung im Kühlkreislauf der PEM-Elektrolyse
No full textIn einer Proton-Exchange-Membrane (PEM) Elektrolyseanlage entsteht an der Anode Sauerstoff, der teils gasförmig und teils gelöst im Prozesswasser vorliegt. Da die Konzentration der gelösten Sauerstoffmoleküle die Löslichkeit überschreitet, kommt es zur Blasenbildung in den Rohrleitungen des Kühlkreislaufes. Ziel dieser Arbeit ist es, die zeit- und längenabhängige Abnahme der Übersättigung und damit die Entwicklung einer Zweiphasenströmung in den Rohrleitungen zwischen Stack und Gasabscheider quantitativ vorherzusagen.
Auf Basis einer Literaturrecherche werden Ansätze zur Beschreibung der einzelnen Schritte der Blasenbildung – Nukleation, Wachstum, Ablösung, Aufstieg und Koaleszenz – zusammengetragen. Darauf aufbauend wird ein Zellenmodell entwickelt, das alle Aspekte der Blasenbildung von der Keimbildung bis zum Wachstum in der Strömung berücksichtigt. Eine Sensitivitätsanalyse untersucht die Einflüsse verschiedener Eingangsparameter des Modells auf die Konzentrationsänderung und identifiziert die Keimstellenanzahl, den Anfangsgasanteil und die Blasengrößenverteilung als dominierende Parameter für die Desorptionskinetik. Zur Verifikation dient ein modularer Versuchsstand mit drei verschieden langen Rohrstrecken und einem Rohrdurchmesser von 20 mm, in welchem Reynoldszahlen zwischen 6.500 und 27.000 betrachtet werden. Ein neu entwickeltes Messverfahren bestimmt dabei die Sauerstoffkonzentration im Wasser am Austritt der Versuchs-strecke; die Messunsicherheit wird systematisch quantifiziert.
Die Experimente belegen, dass unter den gegebenen turbulenten Strömungsbedingungen und einer moderaten Übersättigung von 2,86 selbst nach 10 m noch etwa 50 % der ursprünglichen Übersättigung verbleiben – bei kürzeren Rohrstrecken ist der Anteil sogar noch höher. Das Modell reproduziert die Messdaten am besten mit der Blasenwachstumskorrelation nach Kress & Keyes und verdeutlicht, dass die Annäherung an das thermodynamische Gleichgewicht einer nicht zu vernachlässigten Verzögerung aufgrund der vorherrschenden Kinetik unterliegt. Übertragen auf eine industrielle 20 MW-PEM Anlage legt das Modell selbst mit konservativen Annahmen nahe, dass aufgrund der hohen angenommenen Sauerstoffübersättigung von 40 bis 70 und dem hohen Gasanteil am Stackausgang die Löslichkeit bereits innerhalb der ersten drei Meter vollständig erreicht wird. Die Arbeit leistet damit einen integralen Beitrag zur Auslegung von Rohrleitungen in PEM-Elektrolyse-Kühlkreisläufen sowie anderen zweiphasig-übersättigten Strömungen und zeigt, dass Gleichgewichtsannahmen ohne Berücksichtigung der Kinetik der Blasenentstehung zu Fehldimensionierungen führen können.In a proton exchange membrane (PEM) electrolyser, oxygen is generated at the anode, existing partly as a gas and partly dissolved in the process water. Because the concentration of dissolved oxygen exceeds its solubility, bubbles form in the piping of the cooling circuit. The aim of this thesis is to quantitatively predict the time- and distance-dependent decrease in supersaturation—and thus the devel-opment of a two-phase flow—in the pipes between the stack and the gas separa-tor.
Drawing on an extensive literature survey, approaches for describing the individ-ual steps of bubble formation—nucleation, growth, detachment, rise and coales-cence—are compiled. On this basis, a cell model is developed that captures every aspect of bubble formation from nucleation to in-flow growth. A sensitivity analy-sis examines the influence of various input parameters on the concentration change and identifies the number of nucleation sites, the initial gas fraction and the bubble-size distribution as the dominant factors governing desorption kinet-ics. For validation, a modular test rig with three pipe sections of different lengths (20 mm inner diameter) is employed, covering Reynolds numbers between 6 500 and 27 000. A newly developed measurement technique determines the oxygen concentration in the water at each section’s outlet, and the associated uncertainty is systematically quantified.
The experiments show that, under the prevailing turbulent flow conditions and a moderate super-saturation of 2.86, roughly 50 % of the initial supersaturation still remains after 10 m—and the fraction is even higher for shorter pipe lengths. The model reproduces the data best when the bubble-growth correlation of Kress & Keyes is applied, demonstrating that the approach to thermodynamic equilibrium is substantially delayed by kinetic limitations. When extrapolated to an industrial 20 MW PEM plant, the model—even with conservative assump-tions—suggests that the high oxygen super-saturation of 40 to 70 and the high gas fraction at the stack outlet provides sufficient interfacial area for the solubility limit to be reached within the first three meters.
Accordingly, this work makes an integral contribution to the design of piping in PEM-electrolyser cooling circuits and other two-phase supersaturated flows, showing that equilibrium assumptions that disregard bubble-formation kinetics can lead to significant mis-sizing