Postoperative induction of PCT largely depends on the type of surgery. Intestinal surgery and major operations more often increase PCT, whereas it is normal in the majority of patients after minor and primarily aseptic surgery. PCT can thus be used postoperatively for diagnostic means only when the range of PCT concentrations during the normal course of a certain type of surgery is considered and concentrations are followed up.
The electrochemical activity of modern Fe–N–C electrocatalysts in alkaline media is on par with that of platinum. For successful application in fuel cells (FCs), however, also high durability and longevity must be demonstrated. Currently, a limited understanding of degradation pathways, especially under operando conditions, hinders the design and synthesis of simultaneously active and stable Fe–N–C electrocatalysts. In this work, using a gas diffusion electrode half-cell coupled with inductively coupled plasma mass spectrometry setup, Fe dissolution is studied under conditions close to those in FCs, that is, with a porous catalyst layer (CL) and at current densities up to −125 mA·cm–2. Varying the rate of the oxygen reduction reaction (ORR), we show a remarkable linear correlation between the Faradaic charge passed through the electrode and the amount of Fe dissolved from the electrode. This finding is rationalized assuming that oxygen reduction and Fe dissolution reactions are interlinked, likely through a common intermediate formed during the Fe redox transitions in Fe species involved in the ORR, such as FeN x C y and Fe3C@N–C. Moreover, such a linear correlation allows the application of a simple metricS-numberto report the material’s stability. Hence, in the current work, a powerful tool for a more applied stability screening of different electrocatalysts is introduced, which allows on the one hand fast performance investigations under more realistic conditions, and on the other hand a more advanced mechanistic understanding of Fe–N–C degradation in CLs.
The growth of silver shells on gold nanorods is investigated by in situ liquid cell transmission electron microscopy using an advanced liquid cell architecture. The design is based on microwells in which the liquid is confined between a thin Si 3 N 4 membrane on one side and a few-layer graphene cap on the other side. A well-defined specimen thickness and an ultraflat cell top allow for the application of high-resolution TEM and the application of analytical TEM techniques on the same sample. The combination of high-resolution data with chemical information is validated by radically new insights into the growth of silver shells on cetrimonium bromide stabilized gold nanorods. It is shown that silver bromide particles already formed in the stock solution play an important role in the exchange of silver ions. The Ag shell growth can be directly correlated with the layer-by-layer dissolution of AgBr nanocrystals, which can be controlled by the electron flux density via distinctly generated chemical species in the solvent. The derived model framework is confirmed by in situ UV−vis absorption spectroscopy evaluating the blue shift in the longitudinal surface plasmon resonance of anisotropic NRs in a complementary batch experiment.
Utilizing ionizing radiation for in situ studies in liquid media enables unique insights into nanostructure formation dynamics. As radiolysis interferes with observations, kinetic simulations are employed to understand and exploit beam‐liquid interactions. By introducing an intuitive tool to simulate arbitrary kinetic models for radiation chemistry, it is demonstrated that these models provide a holistic understanding of reaction mechanisms. This is shown for irradiated HAuCl4 solutions allowing for quantitative prediction and tailoring of redox processes in liquid‐phase transmission electron microscopy (LP‐TEM). Moreover, it is demonstrated that kinetic modeling of radiation chemistry is applicable to investigations utilizing X‐rays such as X‐ray diffraction (XRD). This emphasizes that beam‐sample interactions must be considered during XRD in liquid media and shows that reaction kinetics do not provide a threshold dose rate for gold nucleation relevant to LP‐TEM and XRD. Furthermore, it is unveiled that oxidative etching of gold nanoparticles depends on both, precursor concentration, and dose rate. This dependency is exploited to probe the electron beam‐induced shift in Gibbs free energy landscape by analyzing critical radii of gold nanoparticles.
Background: Whole body hyperthermia induced by radiative systems has been used in therapy of malignant diseases for more than ten years. Von Ardenne and co-workers have developed the 'systemiche Krebs-Mehrschritt-Therapic' (sKMT), a combined regime including whole body hyperthermia of 42°C, induced hyperglycaemia and relative hyperoxaemia with additional application of chemotherapy. This concept has been employed in a phase I/II clinical study for patients with metastatic colorectal carcinoma at the Virchow-Klinikum since January 1997. Methods: The sKMT concept was performed eleven times under intravenous general anaesthesia, avoiding volatile anaesthetics. Core temperatures of up to 42°C were reached stepwise by warming with infrared-A-radiation (IRATHERM 2000®). During the whole procedure blood glucose levels of 380-450 mg/dl were maintained as well as PaO 2 levels above 200 mmHg. Extensive invasive monitoring was performed in all patients including measurements with the REF-Ox-Pulmonary artery catheter with continuous measuring of mixed venous saturation (Baxter Explorer®) and invasive monitoring of arterial blood pressure. Data for calculation of hemodynamic and gas exchange parameters were collected four times, at temperatures of 37°C, 40°C, 41.8-42°C and 39°C, during measurements FiO 2 was 1.0 at all times. Fluids were given in order to keep central-venous and Wedge pressure within normal range during the whole procedure. Statistics were performed using the Wilcoxon Test. Results: Statistically significant differences were found between heart rate, cardiac index and systemic vascular resistance comparing data at 37°C and 42°C. Heart rate and cardiac index increased to a maximum at 42°C (P < 0.0001) whereas systemic vascular resistance had its minimum at 42°C (P < 0.0001). Mean arterial pressure dropped with increasing temperature, differences were not significant. Calculation of stroke volume index and ventricular volumes showed only a slight decrease in endsystolic volumes with increasing temperature, the resulting differences in right ventricular ejection fraction were marginally significant (P = 0.038) comparing 42°C to baseline. Right ventricular stroke work index as well as mean pulmonary arterial pressure increased at 42°C (P = 0.0115 and P = 0.0037), pulmonary vascular resistance only dropped little compared to systemic vascular resistance, left ventricular stroke work index even dropped with increasing temperature, though showing no significant difference. Values for mixed venous oxygen saturation did not vary during therapy, pulmonary right-left shunt showed a temperature associated increase (P = 0.0323) to a maximum at 42°C. Conclusion: Under the procedure of sKMT cardiac function in patients, who do not have any pre-existing cardiac impairment, can be maintained almost unchanged, ie with normal right and left ventricular pressure, despite an increase in right ventricular stroke work Acknowledegment: Supported by Deutsche Krebshilfe.
Etching and growth of gold nanoparticles at a solid–liquid–gas interface are investigated via in situ liquid cell transmission electron microscopy. For this purpose, the gold precursor tetrachloroauric acid is enclosed in the wells of a free‐standing, locally thinned silicon nitride film covered by few‐layer graphene. Etching of gold is attributed to hydroxide radicals generated by radiolysis and gaseous species which are located within a gas bubble. The etching mechanism comprises two distinct cases. In one case, the gas bubble is in direct contact with the gold particle, separated only by a thin liquid membrane. In the other case, the gold particle is thoroughly immersed in liquid in the vicinity of the particle. In the latter, etching molecules diffuse from the bubble through the liquid toward the surface of the nanoparticle and subsequently etch the gold platelet. During the particle etching process, concurrent nucleation and ripening of gold nanoparticles are observed. This growth is induced by local supersaturation of the solution with gold ions. Experimental results show that the growth process is limited by diffusion, even though the diffusivity of reactants is very low due to narrow‐channel effects compared against the diffusivity of solvated ions in bulk liquids.
A significant electron-beam induced heating effect is demonstrated for liquid-phase transmission electron microscopy at low electron flux densities using Au nanoparticles as local nanothermometers. The obtained results are in agreement...
The optical detectability of ultrathin conductive films (down to one atomic layer) can be enhanced by choosing distinct layer-stacks. A simple analytical approach using the transfer matrix method is applied for calculating the reflectance of arbitrary multi-layer stack systems with and without the ultrathin layer of interest on top in a wide wavelength range, including both the visible spectrum and the ultraviolet spectrum. Then, the detectability defined by the Michelson contrast was calculated. Performing these calculations for thickness variations of the individual layers in the stack allows determining optimum layer thicknesses, e.g., maximum overall contrast or maximum contrast for a given wavelength. To demonstrate the validity of the methodology, two thin film stacks were investigated, which use p-type silicon as a substrate material and partially covered by a single-layer graphene as a top layer. For each stack, two samples with different layer thicknesses were fabricated and their experimentally determined reflectance was compared to the calculated values. The first system consists of a single SiO2 layer with a thickness of 147nm and 304nm, respectively, and the second is a double layer stack consisting of a Si3N4 layer with a thickness of 54 nm and 195 nm, respectively, on top of an 11 nm SiO2 film. The Michelson contrast of single-layer graphene flakes on the latter layer stacks becomes very high (absolute value of more than 0.3) in the visible wavelength range. Additionally, in the UV-B range a large difference in the reflection of selected SiO2 layer thicknesses on silicon substrates with and without single-layer graphene on top is found with a decrease in the measured reflectance of up to 33%. The measured and calculated values showed a high conformity suggesting this approach usable for the calculation of reflectance and transmittance properties of arbitrary layer stack systems including thin conductive layers
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.