Remote sensing of emperor penguin abundance and breeding success.

Emperor penguins (Aptenodytes forsteri) are under increasing environmental pressure. Monitoring colony size and population trends of this Antarctic seabird relies primarily on satellite imagery recorded near the end of the breeding season, when light conditions levels are sufficient to capture images, but colony occupancy is highly variable. To correct population estimates for this variability, we develop a phenological model that can predict the number of breeding pairs and fledging chicks, as well as key phenological events such as arrival, hatching and foraging times, from as few as six data points from a single season. The ability to extrapolate occupancy from sparse data makes the model particularly useful for monitoring remotely sensed animal colonies where ground-based population estimates are rare or unavailable.

Advances in remote sensing of emperor penguins: first multi-year time series documenting trends in the global population.

Like many polar animals, emperor penguin populations are challenging to monitor because of the species' life history and remoteness. Consequently, it has been difficult to establish its global status, a subject important to resolve as polar environments change. To advance our understanding of emperor penguins, we combined remote sensing, validation surveys and using Bayesian modelling, we estimated a comprehensive population trajectory over a recent 10-year period, encompassing the entirety of the species' range. Reported as indices of abundance, our study indicates with 81% probability that there were fewer adult emperor penguins in 2018 than in 2009, with a posterior median decrease of 9.6% (95% credible interval (CI) -26.4% to +9.4%). The global population trend was -1.3% per year over this period (95% CI = -3.3% to +1.0%) and declines probably occurred in four of eight fast ice regions, irrespective of habitat conditions. Thus far, explanations have yet to be identified regarding trends, especially as we observed an apparent population uptick toward the end of time series. Our work potentially establishes a framework for monitoring other Antarctic coastal species detectable by satellite, while promoting a need for research to better understand factors driving biotic changes in the Southern Ocean ecosystem.

Acceptance of meat reduction policies in Switzerland.

The aim of this study was to analyze the acceptance of different policy measures affecting meat consumption in Switzerland. We conducted qualitative interviews with leading stakeholders and elaborated 37 policy measures for reducing meat consumption. In a standardized survey, we analyzed the acceptance of these measures and important preconditions for their implementation. Measures with potentially the biggest direct leverage, such as a VAT increase on meat products, were highly rejected. We found high levels of acceptance for measures that do not directly affect meat consumption but have the potential for significant changes of meat consumption in the longer run - such as research investment and sustainable diet education. Furthermore, some measures with considerable short-term effects were widely accepted (e.g., stricter animal welfare standards, ban of meat advertisements). These measures could be a promising starting point for policy makers aiming at a transformation of the food system toward lower levels of meat consumption.

Aspirin versus aggressive antiplatelet therapy for acute carotid stenting plus thrombectomy in tandem occlusions: ETIS Registry results.

BACKGROUND: Patients treated with acute carotid stenting (CAS) may have higher odds of a favorable outcome than those treated without CAS during thrombectomy in tandem occlusions. Antiplatelet therapy is associated with CAS to avoid stent thrombosis, which occurs in around 20% of patients and negatively impacts outcomes. In this study we compared two antiplatelet strategies in tandem occlusion strokes treated with CAS and intracranial thrombectomy in clinical practice. METHODS: The Endovascular Treatment in Ischemic Stroke Registry is an ongoing prospective observational study involving 21 comprehensive stroke centers performing thrombectomy in France. We analyzed patients with atherosclerotic tandem occlusions treated with acute CAS and intracranial thrombectomy who received at least one antiplatelet agent. Aggressive antiplatelet therapy included oral or intravenous glycoprotein (GP) IIb/IIIa or P2Y12 inhibitors. The primary outcome was cervical carotid artery patency at day 1 imaging follow-up. RESULTS: Among the 187 included patients, 124 (66.3%) received aspirin alone and 63 (33.7%) received aggressive antiplatelet therapy. There was no significant difference regarding safety outcomes, especially in symptomatic intracerebral hemorrhage, parenchymal hematoma, and procedural complications. There was a significantly higher rate of carotid stent patency at day 1 in the aggressive antiplatelet therapy group (81.7% vs 97.1%, aOR 17.49, 95% CI 1.10 to 277.2, p=0.042). Odds of favorable functional outcome (90-day modified Rankin Scale score 0-2) were similar between the groups (OR 3.04, 95% CI 0.64 to 14.25, p=0.158). CONCLUSIONS: In tandem occlusions treated with CAS plus thrombectomy, an aggressive antiplatelet regimen was associated with an increased rate of carotid stent patency at day 1 without safety concerns. Randomized trials are warranted to confirm these findings.

Influence of prior intravenous thrombolysis in patients treated with mechanical thrombectomy for M2 occlusions: insight from the Endovascular Treatment in Ischemic Stroke (ETIS) registry.

BACKGROUND: Intravenous thrombolysis (IVT) for patients treated with mechanical thrombectomy (MT) for proximal occlusions has recently been questioned through randomized trials. However, few patients with M2 occlusions were included. We investigated the influence of prior IVT for patients presenting M2 occlusions treated with MT in comparison with MT alone. METHODS: We conducted a retrospective analysis of the Endovascular Treatment in Ischemic Stroke (ETIS) registry, a multicenter observational study. Data from consecutive patients treated with MT for M2 occlusions between January 2015 and January 2022 at 26 comprehensive stroke centers were analyzed. The primary endpoint was 90-day modified Rankin Scale score of 0-2. Outcomes were compared using propensity score approaches. We also performed sensitivity analysis in relevant subgroups of patients. RESULTS: Among 1132 patients with M2 occlusions treated with MT, 570 received prior IVT. The two groups were comparable after propensity analysis. The rate of favorable functional outcome was significantly higher in the IVT+MT group compared with the MT alone group (59.8% vs 44.7%; adjusted OR 1.38, 95% CI 1.10 to 1.75, P=0.008). Hemorrhagic and procedural complications were similar in both groups. In sensitivity analysis excluding patients with anticoagulation treatment, favorable recanalization was more frequent in the IVT+MT group (OR 1.37, 95% CI 1.11 to 1.70, P=0.004). CONCLUSIONS: In cases of M2 occlusions, prior IVT combined with MT resulted in better functional outcome than MT alone, without increasing the rate of hemorrhagic or procedural complications. These results suggest the benefit of IVT in patients undergoing MT for M2 occlusions.

Biologging of emperor penguins-Attachment techniques and associated deployment performance.

An increasing number of marine animals are equipped with biologgers, to study their physiology, behaviour and ecology, often for conservation purposes. To minimise the impacts of biologgers on the animals' welfare, the Refinement principle from the Three Rs framework (Replacement, Reduction, Refinement) urges to continuously test and evaluate new and updated biologging protocols. Here, we propose alternative and promising techniques for emperor penguin (Aptenodytes forsteri) capture and on-site logger deployment that aim to mitigate the potential negative impacts of logger deployment on these birds. We equipped adult emperor penguins for short-term (GPS, Time-Depth Recorder (TDR)) and long-term (i.e. planned for one year) deployments (ARGOS platforms, TDR), as well as juvenile emperor penguins for long-term deployments (ARGOS platforms) in the Weddell Sea area where they had not yet been studied. We describe and qualitatively evaluate our protocols for the attachment of biologgers on-site at the colony, the capture of the animals and the recovery of the devices after deployment. We report unprecedented recaptures of long-term equipped adult emperor penguins (50% of equipped individuals recaptured after 290 days). Our data demonstrate that the traditional technique of long-term attachment by gluing the biologgers directly to the back feathers causes excessive feather breakage and the loss of the devices after a few months. We therefore propose an alternative method of attachment for back-mounted devices. This technique led to successful year-round deployments on 37.5% of the equipped juveniles. Finally, we also disclose the first deployments of leg-bracelet mounted TDRs on emperor penguins. Our findings highlight the importance of monitoring potential impacts of biologger deployments on the animals and the need to continue to improve methods to minimize disturbance and enhance performance and results.

Calcium supplementation of bioinks reduces shear stress-induced cell damage during bioprinting.

During bioprinting, cells are suspended in a viscous bioink and extruded under pressure through small diameter printing needles. The combination of high pressure and small needle diameter exposes cells to considerable shear stress, which can lead to cell damage and death. Approaches to monitor and control shear stress-induced cell damage are currently not well established. To visualize the effects of printing-induced shear stress on plasma membrane integrity, we add FM 1-43 to the bioink, a styryl dye that becomes fluorescent when bound to lipid membranes, such as the cellular plasma membrane. Upon plasma membrane disruption, the dye enters the cell and also stains intracellular membranes. Extrusion of alginate-suspended NIH/3T3 cells through a 200µm printing needle led to an increased FM 1-43 incorporation at high pressure, demonstrating that typical shear stresses during bioprinting can transiently damage the plasma membrane. Cell imaging in a microfluidic channel confirmed that FM 1-43 incorporation is caused by cell strain. Notably, high printing pressure also impaired cell survival in bioprinting experiments. Using cell types of different stiffnesses, we find that shear stress-induced cell strain, FM 1-43 incorporation and cell death were reduced in stiffer compared to softer cell types and demonstrate that cell damage and death correlate with shear stress-induced cell deformation. Importantly, supplementation of the suspension medium with physiological concentrations of CaCl2greatly reduced shear stress-induced cell damage and death but not cell deformation. As the sudden influx of calcium ions is known to induce rapid cellular vesicle exocytosis and subsequent actin polymerization in the cell cortex, we hypothesize that calcium supplementation facilitates the rapid resealing of plasma membrane damage sites. We recommend that bioinks should be routinely supplemented with physiological concentrations of calcium ions to reduce shear stress-induced cell damage and death during extrusion bioprinting.

Characterization and Modeling of Nano Wear for Molybdenum-Based Lubrication Layer Systems.

As a result of global economic and environmental change, the demand for innovative, environmentally-friendly technologies is increasing. Employing solid lubricants in rolling contacts can reduce the use of environmentally harmful greases and oils. The aim of the current research was the development of a solid lubricant system with regenerative properties. The layer system consisted of a molybdenum (Mo) reservoir and a top layer of molybdenum trioxide (MoO3). After surface wear, Mo is supposed to react with atmospheric oxygen and form a new oxide. The determination of the wear volume of thin layers cannot be measured microscopically, which is why the wear behavior is initially determined on the nano level. In this work, single Mo and MoO3 coatings prepared by physical vapor deposition (PVD) are characterized by nano testing. The main objective was to determine the wear volume of the single coatings using a newly developed method considering the initial topology. For this purpose, nano-wear tests with different wear paths and normal forces were carried out and measured by in situ scanning probe microscopy (SPM). Based on the characteristic values determined, the coefficient of wear was determined for wear modeling according to Sarkar. The validation of the wear model developed was carried out by further wear tests on the respective mono layers.

Cryopreservation impairs 3-D migration and cytotoxicity of natural killer cells.

Natural killer (NK) cells are important effector cells in the immune response to cancer. Clinical trials on adoptively transferred NK cells in patients with solid tumors, however, have thus far been unsuccessful. As NK cells need to pass stringent safety evaluation tests before clinical use, the cells are cryopreserved to bridge the necessary evaluation time. Standard degranulation and chromium release cytotoxicity assays confirm the ability of cryopreserved NK cells to kill target cells. Here, we report that tumor cells embedded in a 3-dimensional collagen gel, however, are killed by cryopreserved NK cells at a 5.6-fold lower rate compared to fresh NK cells. This difference is mainly caused by a 6-fold decrease in the fraction of motile NK cells after cryopreservation. These findings may explain the persistent failure of NK cell therapy in patients with solid tumors and highlight the crucial role of a 3-D environment for testing NK cell function.

Low Cost, High Performance, 16-Channel Microwave Measurement System for Tomographic Applications.

We have developed a multichannel software defined radio-based transceiver measurement system for use in general microwave tomographic applications. The unit is compact enough to fit conveniently underneath the current illumination tank of the Dartmouth microwave breast imaging system. The system includes 16 channels that can both transmit and receive and it operates from 500 MHz to 2.5 GHz while measuring signals down to -140 dBm. As is the case with multichannel systems, cross-channel leakage is an important specification and must be lower than the noise floors for each receiver. This design exploits the isolation inherent when the individual receivers for each channel are physically separate; however, these challenging specifications require more involved signal isolation techniques at both the system design level and the individual, shielded component level. We describe the isolation design techniques for the critical system elements and demonstrate specification compliance at both the component and system level.

Meisenheimer complexes as hidden intermediates in the aza-SNAr mechanism.

In this work we report a computational study about the aza-SNAr mechanism in fluorine- and chlorine-containing azines with the aim to unravel the physical factors that determine the reactivity patterns in these heterocycles towards propylamine. The nature of the reaction intermediate was analyzed in terms of its electronic structure based on a topological analysis framework in some non-stationary points along the reaction coordinate. The mechanistic dichotomy of a concerted or a stepwise pathway is interpreted in terms of the qualitative Diabatic Model of Intermediate Stabilization (DMIS) approach, providing a general mechanistic picture for the SNAr process involving both activated benzenes and nitrogen-containing heterocycles. With the information collected, a unified vision of the Meisenheimer complexes as transition state, hidden intermediate or real intermediate was proposed.

micrObs - A customizable time-lapse camera for ecological studies.

Camera traps for motion-triggered or continuous time-lapse recordings are readily available on the market. For demanding applications in ecology and environmental sciences, however, commercial systems often lack flexibility to freely adjust recording time intervals, suffer from mechanical component wear, and can be difficult to combine with auxiliary sensors such as GPS, weather stations, or light sensors. We present a robust time-lapse camera system that has been operating continuously since 2013 under the harsh climatic conditions of the Antarctic and Subantarctic regions. Thus far, we have recorded over one million images with individual cameras. The system consumes 122 mW of power in standby mode and captures up to 200,000 high-resolution (16 MPix) images without maintenance such as battery or image memory replacement. It offers time-lapse intervals between 2 s and 1 h, low-light or night-time power saving, and data logging capabilities for additional inputs such as GPS and weather data.

A 4-channel, vector network analyzer microwave imaging prototype based on software defined radio technology.

We have implemented a prototype 4-channel transmission-based, microwave measurement system built on innovative software defined radio (SDR) technology. The system utilizes the B210 USRP SDR developed by Ettus Research that operates over a 70 MHz-6 GHz bandwidth. While B210 units are capable of being synchronized with each other via coherent reference signals, they are somewhat unreliable in this configuration and the manufacturer recommends using N200 or N210 models instead. For our system, N-series SDRs were less suitable because they are not amenable to RF shielding required for the cross-channel isolation necessary for an integrated microwave imaging system. Consequently, we have configured an external reference that overcame these limitations in a compact and robust package. Our design exploits the rapidly evolving technology being developed for the telecommunications environment for test and measurement tasks with the higher performance specifications required in medical microwave imaging applications. In a larger channel configuration, the approach is expected to provide performance comparable to commercial vector network analyzers at a fraction of the cost and in a more compact footprint.

CameraTransform: A Python package for perspective corrections and image mapping.

Camera images and video recordings are simple and non-invasive tools to investigate animals in their natural habitat. Quantitative evaluations, however, often require an exact reconstruction of object positions, sizes, and distances in the image. Here, we provide an open source software package to perform such calculations. Our approach allows the user to correct for perspective distortion, transform images to "bird's-eye" view projections, or transform image-coordinates to real-world coordinates and vice versa. The extrinsic camera parameters that are necessary to perform such image corrections and transformations (elevation, tilt/roll angle, and heading of the camera) are obtained from the image using contextual information such as a visible horizon, GPS coordinates of landmarks, known object sizes, or images of the same object obtained from different viewing angles. All mathematical operations are implemented in the Python package CameraTransform. The performance of the implementation is evaluated using computer-generated synthetic images with known camera parameters. Moreover, we test our algorithm on images of emperor penguin colonies, and demonstrate that the camera tilt and roll angles can be estimated with an error of less than one degree, and the camera elevation with an error of less than 5%. The CameraTransform software package simplifies camera matrix-based image transformations and the extraction of quantitative image information. An extensive documentation and usage examples in an ecological context are provided at http://cameratransform.readthedocs.io.

Secondary Particle Formation during the Nonaqueous Synthesis of Metal Oxide Nanocrystals.

This study aims to elucidate the aggregation and agglomeration behavior of TiO2 and ZrO2 nanoparticles during the nonaqueous synthesis. We found that zirconia nanoparticles immediately form spherical-like aggregates after nucleation with a homogeneous size of 200 nm, which can be related to the metastable state of the nuclei and the reduction of surface free energy. These aggregates further agglomerate, following a diffusion-limited colloid agglomeration mechanism that is additionally supported by the high fractal dimension of the resulting agglomerates. In contrast, TiO2 nanoparticles randomly orient and follow a reaction-limited colloid agglomeration mechanism that leads to a dense network of particles throughout the entire reaction volume. We performed in situ laser light transmission measurements and showed that particle formation starts earlier than previously reported. A complex population balance equation model was developed that is able to simulate particle aggregation as well as agglomeration, which eventually allowed us to distinguish between both phenomena. Hence, we were able to investigate the respective agglomeration kinetics with great agreement to our experimental data.

Structural organisation and dynamics in king penguin colonies.

During breeding, king penguins do not build nests, however they show strong territorial behaviour and keep a pecking distance to neighbouring penguins. Penguin positions in breeding colonies are highly stable over weeks and appear regularly spaced, but thus far no quantitative analysis of the structural order inside a colony has been performed. In this study, we use the radial distribution function to analyse the spatial coordinates of penguin positions. Coordinates are obtained from aerial images of two colonies that were observed for several years. Our data demonstrate that the structural order in king penguin colonies resembles a 2-dimensional liquid of particles with a Lennard-Jones-type interaction potential. We verify this using a molecular dynamics simulation with thermally driven particles, whereby temperature corresponds to penguin movements, the energy well depth e of the attractive potential corresponds to the strength of the colony-forming behaviour, and the repulsive zone corresponds to the pecking radius. We can recapitulate the liquid disorder of the colony, as measured by the radial distribution function, when the particles have a temperature of several (1.4-10) ε/k B and a normally distributed repulsive radius. To account for the observation that penguin positions are stable over the entire breeding period, we hypothesize that the liquid disorder is quenched during the colony formation process. Quenching requires the temperature to fall considerably below 1 ε/k B, which corresponds to a glass transition, or the repulsion radius to exceed the distance between neighbouring penguins, which corresponds to a jamming transition. Video recordings of a breeding colony together with simulations suggest that quenching is achieved by a behavioural motility arrest akin to a glass transition. We suggest that a liquid disordered colony structure provides an ideal compromise between high density and high flexibility to respond to external disturbances that require a repositioning of penguins.

Unbiased High-Precision Cell Mechanical Measurements with Microconstrictions.

We describe a quantitative, high-precision, high-throughput method for measuring the mechanical properties of cells in suspension with a microfluidic device, and for relating cell mechanical responses to protein expression levels. Using a high-speed (750 fps) charge-coupled device camera, we measure the driving pressure Δp, maximum cell deformation εmax, and entry time tentry of cells in an array of microconstrictions. From these measurements, we estimate population averages of elastic modulus E and fluidity ß (the power-law exponent of the cell deformation in response to a step change in pressure). We find that cell elasticity increases with increasing strain εmax according to E ∼ εmax, and with increasing pressure according to E ∼ Δp. Variable cell stress due to driving pressure fluctuations and variable cell strain due to cell size fluctuations therefore cause significant variability between measurements. To reduce measurement variability, we use a histogram matching method that selects and analyzes only those cells from different measurements that have experienced the same pressure and strain. With this method, we investigate the influence of measurement parameters on the resulting cell elastic modulus and fluidity. We find a small but significant softening of cells with increasing time after cell harvesting. Cells harvested from confluent cultures are softer compared to cells harvested from subconfluent cultures. Moreover, cell elastic modulus increases with decreasing concentration of the adhesion-reducing surfactant pluronic. Lastly, we simultaneously measure cell mechanics and fluorescence signals of cells that overexpress the GFP-tagged nuclear envelope protein lamin A. We find a dose-dependent increase in cell elastic modulus and decrease in cell fluidity with increasing lamin A levels. Together, our findings demonstrate that histogram matching of pressure, strain, and protein expression levels greatly reduces the variability between measurements and enables us to reproducibly detect small differences in cell mechanics.

Sumoylation of the GTPase Ran by the RanBP2 SUMO E3 Ligase Complex.

The SUMO E3 ligase complex RanBP2/RanGAP1*SUMO1/Ubc9 localizes at cytoplasmic nuclear pore complex (NPC) filaments and is a docking site in nucleocytoplasmic transport. RanBP2 has four Ran binding domains (RBDs), two of which flank RanBP2's E3 ligase region. We thus wondered whether the small GTPase Ran is a target for RanBP2-dependent sumoylation. Indeed, Ran is sumoylated both by a reconstituted and the endogenous RanBP2 complex in semi-permeabilized cells. Generic inhibition of SUMO isopeptidases or depletion of the SUMO isopeptidase SENP1 enhances sumoylation of Ran in semi-permeabilized cells. As Ran is typically associated with transport receptors, we tested the influence of Crm1, Imp ß, Transportin, and NTF2 on Ran sumoylation. Surprisingly, all inhibited Ran sumoylation. Mapping Ran sumoylation sites revealed that transport receptors may simply block access of the E2-conjugating enzyme Ubc9, however the acceptor lysines are perfectly accessible in Ran/NTF2 complexes. Isothermal titration calorimetry revealed that NTF2 prevents sumoylation by reducing RanGDP's affinity to RanBP2's RBDs to undetectable levels. Taken together, our findings indicate that RanGDP and not RanGTP is the physiological target for the RanBP2 SUMO E3 ligase complex. Recognition requires interaction of Ran with RanBP2's RBDs, which is prevented by the transport factor NTF2.

Coupled molecular switching processes in ordered mono- and multilayers of stimulus-responsive rotaxanes on gold surfaces.

Interfaces provide the structural basis for function as, for example, encountered in nature in the membrane-embedded photosystem or in technology in solar cells. Synthetic functional multilayers of molecules cooperating in a coupled manner can be fabricated on surfaces through layer-by-layer self-assembly. Ordered arrays of stimulus-responsive rotaxanes undergoing well-controlled axle shuttling are excellent candidates for coupled mechanical motion. Such stimulus-responsive surfaces may help integrate synthetic molecular machines in larger systems exhibiting even macroscopic effects or generating mechanical work from chemical energy through cooperative action. The present work demonstrates the successful deposition of ordered mono- and multilayers of chemically switchable rotaxanes on gold surfaces. Rotaxane mono- and multilayers are shown to reversibly switch in a coupled manner between two ordered states as revealed by linear dichroism effects in angle-resolved NEXAFS spectra. Such a concerted switching process is observed only when the surfaces are well packed, while less densely packed surfaces lacking lateral order do not exhibit such effects.

Principal component analysis (PCA)-assisted time-of-flight secondary-ion mass spectrometry (ToF-SIMS): a versatile method for the investigation of self-assembled monolayers and multilayers as precursors for the bottom-up approach of nanoscaled devices.

The production of high-quality self-assembled monolayers (SAMs) followed by layer-by-layer (LbL) self-assembly of macrocycles is essential for nanotechnology applications based on functional surface films. To help interpret the large amount of data generated by a standard ToF-SIMS measurement, principal component analysis (PCA) was used. For two examples, the advantages of a combination of ToF-SIMS and PCA for quality control and for the optimization of layer-by-layer self-assembly are shown. The first example investigates how different cleaning methods influence the quality of SAM template formation. The second example focuses on the LbL self-assembly of macrocycles and the corresponding stepwise surface modification.