Time-resolved X-ray microscopy of nanoparticle aggregates under oscillatory shear

Of all current detection techniques with nanometer resolution, only X-ray microscopy allows imaging nanoparticles in suspension. Can it also be used to investigate structural dynamics? When studying response to mechanical stimuli, the challenge lies in applying them with precision comparable to spatial resolution. In the first shear experiments performed in an X-ray microscope, we accomplished this by inserting a piezo actuator driven shear cell into the focal plane of a scanning transmission X-ray microscope (STXM). Thus shear-induced reorganization of magnetite nanoparticle aggregates could be demonstrated in suspension. As X-ray microscopy proves suitable for studying structural change, new prospects open up in physics at small length scales.Comment: submitted to J. Synchrot. Radia

Effects of friction and surface tide angle of incidence on the coastal generation of internal tides

For the generation of internal waves by long surface waves, the normal-mode equations and solutions that satisfy the boundary conditions in a two-layer system are found analytically. Frictional effects decrease the amplitude of an internal wave over the shelf, changing it from a standing wave to a wave that progresses coastward and decreases the interference on the amplitude of the offshore progressive wave traveling seaward. Model studies, using a two-layer system of fresh water and saline water in a 9.9-m-long channel, gave favorable results relative to the theoretical results

Investigation of the Dzyaloshinskii-Moriya interaction and room temperature skyrmions in W/CoFeB/MgO thin films and microwires

Recent studies have shown that material structures, which lack structural inversion symmetry and have high spin-orbit coupling can exhibit chiral magnetic textures and skyrmions which could be a key component for next generation storage devices. The Dzyaloshinskii-Moriya Interaction (DMI) that stabilizes skyrmions is an anti-symmetric exchange interaction favoring non-collinear orientation of neighboring spins. It has been shown that material systems with high DMI can lead to very efficient domain wall and skyrmion motion by spin-orbit torques. To engineer such devices, it is important to quantify the DMI for a given material system. Here we extract the DMI at the Heavy Metal (HM) /Ferromagnet (FM) interface using two complementary measurement schemes namely asymmetric domain wall motion and the magnetic stripe annihilation. By using the two different measurement schemes, we find for W(5 nm)/Co20Fe60B20(0.6 nm)/MgO(2 nm) the DMI to be 0.68 +/- 0.05 mJ/m2 and 0.73 +/- 0.5 mJ/m2, respectively. Furthermore, we show that this DMI stabilizes skyrmions at room temperature and that there is a strong dependence of the DMI on the relative composition of the CoFeB alloy. Finally we optimize the layers and the interfaces using different growth conditions and demonstrate that a higher deposition rate leads to a more uniform film with reduced pinning and skyrmions that can be manipulated by Spin-Orbit Torques

Continuous infusion of physostigmine in patients with perioperative septic shock: A pharmacokinetic/pharmacodynamic study with population pharmacokinetic modeling

Background In the context of the cholinergic anti-inflammatory pathway, the clinical trial Anticholium® per Se (EudraCT Number: 2012-001650-26, ClinicalTrials.gov NCT03013322) addressed the possibility of taking adjunctive physostigmine salicylate treatment in septic shock from bench to bedside. Pharmacokinetics (PK) are likely altered in critically ill patients; data on physostigmine PK and target concentrations are sparse, particularly for continuous infusion. Our objective was to build a population PK (popPK) model for physostigmine, and further evaluate pharmacodynamics (PD) and concentration-response relationship in this setting. Methods In the randomized, double-blind, placebo-controlled trial, 20 patients with perioperative septic shock either received an initial dose of 0.04 mg/kg physostigmine salicylate, followed by continuous infusion of 1 mg/h for up to 120 h, or equivalent volumes of 0.9% sodium chloride (placebo group). Physostigmine plasma concentrations and acetylcholinesterase (AChE) activity were measured; concentration-response associations were evaluated, and popPK and PD modeling was performed with NONMEM. Results Steady state physostigmine plasma concentrations reached 7.60 ± 2.81 ng/mL (mean ± standard deviation [SD]). PK was best described by a two-compartment model with linear clearance. Significant covariate effects were detected for body weight and age on clearance, as well as a high inter-individual variability of the central volume of distribution. AChE activity was significantly reduced to 30.5%–50.6% of baseline activity during physostigmine salicylate infusion. A sigmoidal direct effect PD model best described enzyme inhibition by physostigmine, with an estimated half maximal effective concentration (EC50) of 5.99 ng/mL. Conclusions PK of physostigmine in patients with septic shock displayed substantial inter-individual variability with body weight and age influencing the clearance. Physostigmine inhibited AChE activity with a sigmoidal concentration-response effect

High-Resolution Kinoform X-Ray Optics Printed via 405 nm 3D Laser Lithography

Efficient focusing of X-rays is essential for high-resolution X-ray microscopy. Diffractive X-ray optics called kinoforms offer the highest focusing efficiencies in theory. However, they have long remained unavailable due to their challenging nanofabrication. Recently, various X-ray optic geometries including kinoforms have been realized using 3D laser lithography at near-infrared wavelengths. As the smallest features (period) of the kinoform determines the resolving power, there is a natural drive to find ways to fabricate kinoforms with ever smaller features. Here, a custom-built 3D laser lithography setup with an excitation wavelength of 405 nm is used, which allows to half the smallest period of the kinoforms compared to previous work. A 40% improvement in scanning transmission X-ray microscopy image resolution, that is, a cutoff resolution of 145 nm, and an efficiency of 7.6% at 700 eV is achieved. A reconstructed pixel size of 18.5 nm, reaching the limit imposed by the design of the microscopy set-up, is demonstrated through ptychographic imaging of a magnetic sample which has a strongly reduced contrast mechanism. Moreover, X-ray lenses manufactured by 405 nm 3D laser lithography have the potential to become much less expensive than X-ray lenses made by other means

The 63^{63}Ni(n,γ\gamma) cross section measured with DANCE

The neutron capture cross section of the s-process branch nucleus $^{63}$Ni affects the abundances of other nuclei in its region, especially $^{63}$Cu and $^{64}$Zn. In order to determine the energy dependent neutron capture cross section in the astrophysical energy region, an experiment at the Los Alamos National Laboratory has been performed using the calorimetric 4$\pi$ BaF$_2$ array DANCE. The (n,$\gamma$) cross section of $^{63}$Ni has been determined relative to the well known $^{197}$Au standard with uncertainties below 15%. Various $^{63}$Ni resonances have been identified based on the Q-value. Furthermore, the s-process sensitivity of the new values was analyzed with the new network calculation tool NETZ.Comment: 11 pages, 13 page

How much of Me do I see in You: Neural correlates of self-other distinction in the affective domain

When inferring mental states of others, individuals’ judgments are influenced by their own state of mind, which has been referred to as egocentric bias. Especially in situations where one holds a different mental state than another person to be interpreted, self-other differentiation is key for an accurate interpretation on the other person’s mind. It has been suggested that the right supramarginal gyrus (rSMG) is involved in self-other differentiation and overcoming egocentric bias in the affective domain. In a double-blind, randomized study 47 healthy adults received active or sham anodal tDCS (1mA, 20min) or a sham stimulation to the rSMG prior to performing a newly developed emotional egocentricity paradigm (SOFE, Self-Other Facial Emotion Judgment Task). In SOFE, subjects are presented with emotionally ambiguous situations (happy or fearful) in which they have to continuously rate 1) their own emotion and 2) the emotion of another person whose facial expression is either congruent or incongruent to the subject’s emotion. Analyses confirmed the presence of an emotional egocentric bias in incongruent trials. We furthermore found that active tDCS applied to the rSMG increased subjects’ ability to overcome egocentric judgments. This effect was valence dependent with significant effects when inferring affective states of happy faces right after imagining oneself in a fear-evoking situation (p<0.05). Our findings extend previous research showing a causal role of the rSMG for emotional self-other distinction to the inferring of emotional states from pictorial stimuli. They additionally point towards valence-specific patterns of rSMG functionality. In a next step the SOFE task will be applied in autism spectrum disorder to characterize egocentric bias suppression and SMG network integrity in an effort to elucidate social cognitive dysfunction in affected individuals

The freeze-shut of a convectively cooled parallel plate channel subjected to laminar internal liquid flow

The paper presents an approximative solution for the time dependent development of the ice layers at the cooled walls inside a parallel plate channel. The upper and the lower wall of the channel are cooled by an uniform external convection. By assuming a constant pressure drop across the channel, the freeze-shut of the planar channel could be calculated approximately. It was found out that the origin of the freezing fronts moves upstream during the ice layer growth. Furthermore a simple criterion is presented to predict whether a given system will lead to blockade.Die vorliegende Arbeit stellt eine Approximationslösung vor, die das instationäre Wachstum der Eisschichten in einem ebenen, laminar durchströmten Kanal beschreibt. Die obere und die untere Wand des Kanals werden hierbei konvektiv gekühlt. Unter der Annahme eines zeitlich konstanten Druckverlustes im Kanal ist es möglich, das instationäre Verhalten der Erstarrungsfronten, bis hin zur Blockade des Kanals, approximativ zu berechnen. Als ein Ergebnis der Arbeit ergibt sich, daß der örtliche Beginn der erstarrten Schicht an der Kanalwand mit dicker werdenden Eisschichten stromaufwärts wandert. Weiterhin wird ein Kriterium angegeben, das es erlaubt, a priori darüber zu entscheiden, ob das System bei den vorliegenden Verhältnissen zufriert