8 research outputs found
About the Role of Surfactants on the Magnetic Control over Liquid Interfaces
The behavior of magnetically responsive
aqueous FeÂ(III) surfactant
solutions at liquid interfaces is analyzed. Such surfactants attracted
much attention, because of the ability to manipulate interfaces by
magnetic ïŹelds without any use of magnetic nanoparticles. A detailed analysis of the surface
properties proves that the mixing of paramagnetic electrolyte solution
with anionic, cationic and nonionic surfactants yields the similar
magnetic response and no effect of the surfactant charge can be observed.
We conclude that the observed magnetic shiftability of interfaces
is caused by a combination of the paramagnetic behavior of the bulk
liquid and a reduction of the surface tension. Thus, this work gives
an alternative interpretation of the properties of âmagnetic
surfactantsâ compared to the ones claimed in the literature
On the Spontaneous Formation of Clathrate Hydrates at WaterâGuest Interfaces
The formation of hydrates, cage-like water-gas structures,
is of
tremendous importance both in industries and research. Although of
major significance, the formation process is not completely understood
so far. We present a comprehensive study of hydrate formation at liquidâliquid
interfaces between water and isobutane, propane, carbon dioxide, and
at the liquidâgas interface between water and xenon. We investigated
the structure of these interfaces under quiescent conditions in situ
by means of X-ray reflectivity measurements both inside and outside
the zone of hydrate stability. At the interfaces between water and
liquid alkanes, no evidence for a structural change was found. In
contrast, the accumulation of guest molecules inside nanothick interfacial
layers was observed at the waterâxenon and liquidâliquid
waterâCO<sub>2</sub> interfaces. We show that only those systems
initially exhibiting such guest-enriched interfacial layers developed
into macroscopic gas hydrates within our observation times (âŒ12
h). Therefore, these layers act as triggers for the spontaneous formation
of macroscopic hydrates
Understanding the Surface Regeneration and Reactivity of Garnet Solid-State Electrolytes
Garnet solid-electrolyte-based Li-metal batteries can
be used in
energy storage devices with high energy densities and thermal stability.
However, the tendency of garnets to form lithium hydroxide and carbonate
on the surface in an ambient atmosphere poses significant processing
challenges. In this work, the decomposition of surface layers under
various gas environments is studied by using two surface-sensitive
techniques, near-ambient-pressure X-ray photoelectron spectroscopy
and grazing incidence X-ray diffraction. It is found that heating
to 500 °C under an oxygen atmosphere (of 1 mbar and above) leads
to a clean garnet surface, whereas low oxygen partial pressures (i.e.,
in argon or vacuum) lead to additional graphitic carbon deposits.
The clean surface of garnets reacts directly with moisture and carbon
dioxide below 400 and 500 °C, respectively. This suggests that
additional CO2 concentration controls are needed for the
handling of garnets. By heating under O2 along with avoiding
H2O and CO2, symmetric cells with less than
10 Ωcm2 interface resistance are prepared without
the use of any interlayers; plating currents of >1 mA cmâ2 without dendrite initiation are demonstrated
Solid-Supported Lipid Multilayers under High Hydrostatic Pressure
In this work, the structure of solid-supported
lipid multilayers
exposed to increased hydrostatic pressure was studied <i>in situ</i> by X-ray reflectometry at the solidâliquid interface between
silicon and an aqueous buffer solution. The layersâ vertical
structure was analyzed up to a maximum pressure of 4500 bar. The multilayers
showed phase transitions from the fluid into different gel phases.
With increasing pressure, a gradual filling of the sublayers between
the hydrophilic head groups with water was observed. This process
was inverted when the pressure was decreased, yielding finally smaller
water layers than those in the initial state. As is commonly known,
water has an abrasive effect on lipid multilayers by the formation
of vesicles. We show that increasing pressure can reverse this process
so that a controlled switching between multi- and bilayers is possible
Data_Sheet_1_Recirculation in single lumen cannula venovenous extracorporeal membrane oxygenation: A non-randomized bi-centric trial.pdf
BackgroundRecirculation is a common problem in venovenous (VV) extracorporeal membrane oxygenation (ECMO). The aims of this study were to compare recirculation fraction (Rf) between femoro-jugular and jugulo-femoral VV ECMO configurations, to identify risk factors for recirculation and to assess the impact on hemolysis.MethodsPatients in the medical intensive care unit (ICU) at the University Medical Center Regensburg, Germany receiving VV ECMO with femoro-jugular, and jugulo-femoral configuration at the ECMO Center Karolinska, Sweden, were included in this non-randomized prospective study. Total ECMO flow (QEC), recirculated flow (QREC), and recirculation fraction Rf = QREC/QEC were determined using ultrasound dilution technology. Effective ECMO flow (QEFF) was defined as QEFF = QEC * (1âRf). Demographics, cannula specifics, and markers of hemolysis were assessed. Survival was evaluated at discharge from ICU.ResultsThirty-seven patients with femoro-jugular configuration underwent 595 single-point measurements and 18 patients with jugulo-femoral configuration 231 measurements. Rf was lower with femoro-jugular compared to jugulo-femoral configuration [5 (0, 11) vs. 19 (13, 28) %, respectively (p EFF [2.80 (2.21, 3.39) vs. 2.79 (2.39, 3.08) L/min (p = 0.225)] despite lower QEC with femoro-jugular configuration compared to jugulo-femoral [3.01 (2.40, 3.70) vs. 3.57 (3.05, 4.06) L/min, respectively (p 8 vs. †8%. Explorative data on survival showed comparable results in the femoro-jugular and the jugulo-femoral group (81 vs. 72%, p = 0.455).ConclusionVV ECMO with femoro-jugular configuration caused less recirculation. Further risk factors for higher Rf were shorter distance between the two cannula tips, higher ECMO flow, and lower heart rate. Rf did not affect hemolysis.</p
Different Breathing Mechanisms in Flexible Pillared-Layered MetalâOrganic Frameworks: Impact of the Metal Center
The
pillared-layered metalâorganic framework compounds M<sub>2</sub>(BME-bdc)<sub>2</sub>(dabco) (M<sup>2+</sup> = Zn<sup>2+</sup>, Co<sup>2+</sup>, Ni<sup>2+</sup>, Cu<sup>2+</sup>; BME-bdc<sup>2â</sup> = 2,5-bisÂ(2-methoxyethoxy)-1,4-benzenedicarboxylate;
dabco = diazabicyclo[2.2.2]Âoctane) exhibit structural flexibility
and undergo guest and temperature-induced reversible phase transitions
between a narrow pore (<b>np</b>) and a large pore (<b>lp</b>) form. These transitions were analyzed in detail by powder X-ray
diffraction <i>ex</i> and in situ, isothermal gas adsorption
measurements and differential scanning calorimetry. The threshold
parameters (gas pressure or temperature), the magnitude of the phase
transitions (volume change) as well as their transition enthalpies
are strikingly dependent on the chosen metal cation M<sup>2+</sup>. This observation is assigned to the different electronic structures
and ligand field effects on the coordination bonds. Accordingly, in
situ powder X-ray diffraction measurements as a function of CO<sub>2</sub> pressure reveal different mechanisms for the <b>np</b> to <b>lp</b> phase transition during CO<sub>2</sub> adsorption
Subsurface Influence on the Structure of Protein Adsorbates as Revealed by in Situ X-ray Reflectivity
The adsorption process of proteins to surfaces is governed
by the
mutual interactions among proteins, the solution, and the substrate.
Interactions arising from the substrate are usually attributed to
the uppermost atomic layer. This actual surface defines the surface
chemistry and hence steric and electrostatic interactions. For a comprehensive
understanding, however, the interactions arising from the bulk material
also have to be considered. Our protein adsorption experiments with
globular proteins (α-amylase, bovine serum albumin, and lysozyme)
clearly reveal the influence of the subsurface material via van der
Waals forces. Here, a set of functionalized silicon wafers enables
a distinction between the effects of surface chemistry and the subsurface
composition of the substrate. Whereas the surface chemistry controls
whether the individual proteins are denatured, the strength of the
van der Waals forces affects the final layer density and hence the
adsorbed amount of proteins. The results imply that van der Waals
forces mainly influence surface processes, which govern the structure
formation of the protein adsorbates, such as surface diffusion and
spreading
Adsorption Behavior of Lysozyme at Titanium OxideâWater Interfaces
We
present an in situ X-ray reflectivity study of the adsorption
behavior of the protein lysozyme on titanium oxide layers under variation
of different thermodynamic parameters, such as temperature, hydrostatic
pressure, and pH value. Moreover, by varying the layer thickness of
the titanium oxide layer on a silicon wafer, changes in the adsorption
behavior of lysozyme were studied. In total, we determined less adsorption
on titanium oxide compared with silicon dioxide, while increasing
the titanium oxide layer thickness causes stronger adsorption. Furthermore,
the variation of temperature from 20 to 80 °C yields an increase
in the amount of adsorbed lysozyme at the interface. Additional measurements
with variation of the pH value of the system in a region between pH
2 and 12 show that the surface charge of both protein and titanium
oxide has a crucial role in the adsorption process. Further pressure-dependent
experiments between 50 and 5000 bar show a reduction of the amount
of adsorbed lysozyme with increasing pressure