Fabrication of comb-drive actuators for straining nanostructured suspended graphene

We report on the fabrication and characterization of an optimized comb-drive actuator design for strain-dependent transport measurements on suspended graphene. We fabricate devices from highly p-doped silicon using deep reactive ion etching with a chromium mask. Crucially, we implement a gold layer to reduce the device resistance from $\approx51.6$ k$\mathrm{\Omega}$ to $\approx236$ $\mathrm{\Omega}$ at room temperature in order to allow for strain-dependent transport measurements. The graphene is integrated by mechanically transferring it directly onto the actuator using a polymethylmethacrylate membrane. Importantly, the integrated graphene can be nanostructured afterwards to optimize device functionality. The minimum feature size of the structured suspended graphene is 30 nm, which allows for interesting device concepts such as mechanically-tunable nanoconstrictions. Finally, we characterize the fabricated devices by measuring the Raman spectrum as well as the a mechanical resonance frequency of an integrated graphene sheet for different strain values.Comment: 10 pages, 9 figure

3p photoabsorption of free and bound Cr, Cr⁺, Mn, and Mn⁺

A dual-laser-plasma technique has been used to measure photoabsorption by atomic Cr and Mn and their ions at photon energies between 40 and 70 eV, where the dominant absorption mechanism is excitation of the 3p subshell. No dramatic differences are observed between the absorption spectra of Mn and Mn+, and these spectra are similar to those of Mn metal and MnCl2. The spectra of Cr and Cr+ are strikingly dissimilar, the mean excitation energy being about 5 eV greater in the ion. We attribute this to strong mixing of the localized 3d6 configuration with 3d5nd Rydberg configurations, an effect that is also responsible for the anomalous appearance of the Cr spectrum with respect to those of the other iron-period elements. The absorption spectra of Cr metal and CrCl2 take forms intermediate between those of Cr and Cr+. We give spectroscopic assignments to most of the sharp absorption features of Cr+ and determine the 3p ionization thresholds from quantum-defect analysis

Enhanced rates of regional warming and ocean acidification after termination of large-scale ocean alkalinization

Termination effects of large‐scale Artificial Ocean Alkalinization (AOA) have received little attention because AOA was assumed to pose low environmental risk. With the Max‐Planck‐Institute Earth System Model, we use emission‐driven AOA simulations following the Representative Concentration Pathway 8.5 (RCP8.5). We find that after termination of AOA warming trends in regions of the Northern hemisphere become ∼50% higher than those in RCP8.5 with rates similar to those caused by termination of solar geoengineering over the following three decades after cessation (up to 0.15 K/year). Rates of ocean acidification after termination of AOA outpace those in RCP8.5. In warm shallow regions where vulnerable coral reefs are located, decreasing trends in surface pH double (0.01 units/year) and the drop in the carbonate saturation state (Ω) becomes up to one order of magnitude larger (0.2 units/year). Thus, termination of AOA poses higher risks to biological systems sensitive to fast‐paced environmental changes than previously thought. <br

In-vitro activation of complement system by lactic acidosis in newborn and adults.

INTRODUCTION: Complement activation occurs secondary to a variety of external stimuli. Lactic acidosis has been previously shown to activate the complement factors C3a and C5a. In the present investigation we examined the differential effect of lactic acidosis on anaphylatoxin levels in cord and adult blood. Furthermore we aimed to determine if the entire complement cascade could be activated by lactic acidosis. METHODS: Cord and adult blood samples (n = 20 each) were collected and incubated for one hour in either untreated condition or with the addition of lactate in two concentrations (5.5 mmol/l vs. 22 mmol/l). Following incubation, levels of C3a, C5a and sC5b-9, and blood gas parameters were determined. RESULTS: Anaphylatoxin (C3a and C5a) and sC5b-9 levels increased with the addition of lactate in a dose-dependent manner in cord and adult blood (C3a: 1 h, 5.5 mmo/l, 22 mmol/l: 418/498/622 microg/l in cord blood; 1010/1056/1381 microg/l in adult blood, p<0,05; similar results were found for C5a and sC5b-9). CONCLUSION: Lactic acidosis leads to an activation of the entire complement system in neonates and in adults. This activation is dose-dependent and more pronounced in adults as compared to neonates

Short-term heat treatment of ti6al4v eli as implant material

Due to its mechanical properties and good biocompatibility, Ti6Al4V ELI (extra low interstitials) is widely used in medical technology, especially as material for implants. The specific microstructures that are approved for this purpose are listed in the standard ISO 20160:2006. Inductive short-term heat treatment is suitable for the adjustment of near-surface component properties such as residual stress conditions. A systematic evaluation of the Ti6Al4V microstructures resulting from short-term heat treatment is presently missing. In order to assess the parameter field that leads to suitable microstructures for load-bearing implants, dilatometer experiments have been conducted. For this purpose, dilatometer experiments with heating rates up to 1000 °C/s, holding times between 0.5 and 30 s and cooling rates of 100 and 1000 °C/s were systematically examined in the present study. Temperatures up to 950 °C and a holding time of 0.5 s led to microstructures, which are approved for medical applications according to the standard ISO 20160:2006. Below 950 °C, longer holding times can also be selected

Integrated impedance bridge for absolute capacitance measurements at cryogenic temperatures and finite magnetic fields

We developed an impedance bridge that operates at cryogenic temperatures (down to 60 mK) and in perpendicular magnetic fields up to at least 12 T. This is achieved by mounting a GaAs HEMT amplifier perpendicular to a printed circuit board containing the device under test and thereby parallel to the magnetic field. The measured amplitude and phase of the output signal allows for the separation of the total impedance into an absolute capacitance and a resistance. Through a detailed noise characterization, we find that the best resolution is obtained when operating the HEMT amplifier at the highest gain. We obtained a resolution in the absolute capacitance of 6.4~aF$/\sqrt{\textrm{Hz}}$ at 77 K on a comb-drive actuator, while maintaining a small excitation amplitude of 15~$k_\text{B} T/e$. We show the magnetic field functionality of our impedance bridge by measuring the quantum Hall plateaus of a top-gated hBN/graphene/hBN heterostructure at 60~mK with a probe signal of 12.8~$k_\text{B} T/e$.Comment: 7 pages, 5 figure

Biosensing platform combining label-free and labelled analysis using Bloch surface waves

Bloch surface waves (BSW) propagating at the boundary of truncated photonic crystals (1D-PC) have emerged as an attractive approach for label-free sensing in plasmon-like sensor configurations. Due to the very low losses in such dielectric thin film stacks, BSW feature very low angular resonance widths compared to the surface plasmon resonance (SPR) case. Besides label-free operation, the large field enhancement and the absence of quenching allow utilizing BSW coupled fluorescence detection to additionally sense the presence of fluorescent labels. This approach can be adapted to the case of angularly resolved resonance detection, thus giving rise to a combined label-free / labelled biosensor platform. It features a parallel analysis of multiple spots arranged as a one-dimensional array inside a microfluidic channel of a disposable chip. Application of such a combined biosensing approach to the detection of the Angiopoietin-2 cancer biomarker in buffer solutions is reported

Complement activation by in vivo neonatal and in vitro extracorporeal membrane oxygenation.

Complment activation during extracorporeal membrane oxygenation (ECMO) in newborns can be caused by both the underlying disease processes and by blood contact with the ECMO circuit. We investigated the relative importance of these mechanisms by measuring C3a, C5a and sC5b-9 before, during and after neonatal ECMO in six consecutive newborn patients using enzyme-linked immunoassay. In addition complement activation during in vitro ECMO with repeated flow of the same blood volume was measured using blood from healthy adult donors. C3a increased significantly in vivo after 1 h (from 1035+/-193 to 1865+/-419 microg/l) and in vitro ECMO (from 314+/-75 to 1962+/-1062 microg/l). C5a increased during ECMO without significant differences between in vivo and in vitro activation. In neonatal patients, sC5b-9 rose faster than in vitro, but the rapid increase was also significant for in vitro experiments (in vivo: from 328+/-63 to 1623+/-387 microg/l after 2 h; and in vitro: from 78+/-32 to 453+/-179 microg/l after 8 h). After this initial peak at 1-2 h, complement activation decreased gradually until 2-3 days after the initiation of ECMO. We conclude that in newborns the rapid activation of the complement system after the start of ECMO is predominantly caused by contact with artificial surfaces rather than the patient's underlying disease