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Alzheimer’s disease and depressive disorder are frequent in old age. Both may be associated with depressed mood and cognitive impairment. Therefore, finding a strategy to clarify the diagnosis underlying subjective complaints of impaired cognition and depressed mood in older persons is of utmost interest. We conducted a cross-sectional retrospective observational clinical cohort study using patient records from 2014 to 2018. From 3758 patients, we included patients aged 60 years and older with a Mini-Mental-Status Examination score of 24 and above. Final analysis included all patients in whom Alzheimer’s disease biomarker analysis was performed (cerebrospinal fluid markers of Alzheimer’s disease or positron emission tomography imaging; n = 179) and patients with depressive disorder in whom Alzheimer’s disease was ruled out by analysis of biomarkers suggestive of Alzheimer’s disease (n = 70). With case–control matching for age, education and gender, performance of patients with Alzheimer’s disease was worse in acquisition, consolidation and recall of verbal information and false-positive answers. None of the results, however, sufficed to differentially diagnose individual patients with Alzheimer’s disease or depressive disorder. With more severe symptoms of depression, patients with biomarker-verified Alzheimer’s disease performed worse in executive testing but were not additionally impaired in verbal episodic memory performance. We conclude that distinguishing between Alzheimer’s disease and depressive disorder is unreliable on clinical grounds and behavioural testing alone. Diagnosing the cause of subjective complaints about deteriorating cognitive function or depressed mood requires additional biomarker assessment, whereas cognitive assessment is needed to define appropriate targets of symptomatic treatment in patients with Alzheimer’s disease and depressive disorder., Both Alzheimer’s disease and depressive disorder may be associated with depressed mood and cognitive impairment. Distinguishing between the two conditions on clinical and behavioural grounds alone is unreliable. Diagnosing the cause of subjective complaints about deteriorating cognitive function or depressed mood requires additional biomarker assessment., Graphical Abstract

Spin diffusion type polarization transfer among heteronuclei e.g. 13C or 15N plays an important role in many solid state NMR experiments for structure determination of proteins. In such experiments chemical shift compensation is provided by the proton bath (‘proton driven’) which can be improved by radio frequency irradiation of the protons. Here we address the problem that the polarization transfer rates depend not only on the intermolecular distance but also on the chemical shift difference of the two spins. We introduce rf modulation schemes that allow eliminating the chemical shift dependence to a large extent over a predefined range. At the same time the rate constants are maximized.

In this article, we describe third-spin assisted heteronuclear recoupling experiments, which play an increasingly important role in measuring long-range heteronuclear couplings, in particular (15)N-(13)C, in proteins. In the proton-assisted insensitive nuclei cross polarization (PAIN-CP) experiment (de Paepe et al. in J Chem Phys 134:095101, 2011), heteronuclear polarization transfer is always accompanied by homonuclear transfer of the proton-assisted recoupling (PAR) type. We present a phase-alternating experiment that promotes heteronuclear (e.g. (15)N → (13)C) polarization transfer while simultaneously minimizing homonuclear (e.g.(13)C → (13)C) transfer (PAIN without PAR). This minimization of homonuclear polarization transfer is based on the principle of the resonant second-order transfer (RESORT) recoupling scheme where the passive proton spins are irradiated by a phase-alternating sequence and the modulation frequency is matched to an integer multiple of the spinning frequency. The similarities and differences between the PAIN-CP and this het-RESORT experiment are discussed here.

SUMMARY Pitcher plants of the genus Nepenthes efficiently trap and retain insect prey in highly specialized leaves. Besides a slippery peristome which inhibits adhesion of insects they employ epicuticular wax crystals on the inner walls of the conductive zone of the pitchers to hamper insect attachment by adhesive devices. It has been proposed that the detachment of individual crystals and the resulting contamination of adhesive organs is responsible for capturing insects. However, our results provide evidence in favour of a different mechanism, mainly based on the stability and the roughness of the waxy surface. First, we were unable to detect a large quantity of crystal fragments on the pads of insects detached from mature pitcher surfaces of Nepenthes alata. Second, investigation of the pitcher surface by focused ion beam treatment showed that the wax crystals form a compact 3D structure. Third, atomic force microscopy of the platelet-shaped crystals revealed that the crystals are mechanically stable, rendering crystal detachment by insect pads unlikely. Fourth, the surface profile parameters of the wax layer showed striking similarities to those of polishing paper with low grain size. By measuring friction forces of insects on this artificial surface we demonstrate that microscopic roughness alone is sufficient to minimize insect attachment. A theoretical model shows that surface roughness within a certain length scale will prevent adhesion by being too rough for adhesive pads but not rough enough for claws.

We describe a resonant second-order dipolar recoupling condition for magic-angle spinning (MAS) solid-state NMR where the active spins are irradiated by continuous-wave irradiation and the passive spins by a phase-alternating sequence. The phase-modulation frequency is matched to an integer multiple of the MAS frequency to produce a second-order homonuclear dipolar coupling Hamiltonian that promotes broadband homonuclear zero-quantum polarization transfer on the spin-locked active spins. The recoupling sequence is based on second-order cross terms between two heteronuclear dipolar couplings. Similarities and differences to the proton-assisted recoupling sequence are discussed.

Spin-diffusion measurements are applied in many solid-state NMR experiments. They require the preparation of non-equilibrium polarization on one spin species (S spins) which is often done through polarization transfer from a second spin species (I-spin). Such experiments involve radio-frequency irradiation at the Larmor frequencies of both spins. Here, we describe a method to generate and detect S-spin ( 13 C) difference polarization via the I spins ( 1 H) without S-spin pulses. No coil tuned to the S-spin ( 13 C) resonance frequency is needed. On the basis of such a transfer step, S-spin spin diffusion can be measured in a single-channel I-spin ( 1 H) experiment.

SUMMARY Knowledge of both surface structure and physical properties such as stiffness and elasticity are essential to understanding any adhesive system. In this study of an adhesion surface in the tree frog, Litoria caerulea White, a variety of techniques including atomic force microscopy were used to investigate the microstructure and properties of an epithelium that adheres through wet adhesion. Litoria toe pads consist of a hexagonal array of flat-topped epithelial cells, separated by mucus-filled channels. Under an atomic force microscope, this `flat' surface is highly structured at the nanoscale, consisting of a tightly packed array of columnar nanopillars (described as hemidesmosomes by previous authors), 326±84 nm in diameter, each of which possesses a central dimple 8±4 nm in depth. In fixed tissue (transmission electron microscopy), the nanopillars are approximately as tall as they are broad. At the gross anatomical level, larger toe pads may be subdivided into medial and lateral parts by two large grooves. Although the whole toe pad is soft and easily deformable, the epithelium itself has an effective elastic modulus equivalent to silicon rubber (mean Eeff=14.4±20.9 MPa; median Eeff=5.7 MPa), as measured by the atomic force microscope in nanoindentation mode. The functions of these structures are discussed in terms of maximising adhesive and frictional forces by conforming closely to surface irregularities at different length scales and maintaining an extremely thin fluid layer between pad and substrate. The biomimetic implications of these findings are reviewed.

We describe a low-power approach for heteronuclear cross-polarization (CP) at high magic-angle spinning (MAS) frequencies. It is based on second-order CP at the n = 0 Hartmann–Hahn condition. The mechanism for the polarization transfer in the low-power CP experiment relies on second-order cross terms between homonuclear and heteronuclear dipolar couplings. At a MAS frequency of 65 kHz, rf-field amplitudes below 10 kHz are sufficient to efficiently transfer polarization from 1 H to 13 C. The low-rf field requirements of this approach make it well suited for the investigation of proteins and other temperature-sensitive samples without the risk of sample heating and degradation.

We introduce a second-order dipolar recoupling condition for magic-angle spinning NMR where the isotropic chemical-shift difference of two homonuclear S spins is matched by the rf-irradiation amplitude, or, alternatively, phase-modulation frequency, on a heteronuclear spin. The experiment can be looked at as a mixed rotational and rotary-resonance condition (MIRROR). The effective MIRROR Hamiltonian promotes homonuclear zero-quantum polarization transfer and heteronuclear zero-quantum and double-quantum polarization transfer. The MIRROR recoupling condition is applied to obtain enhanced polarization transfer through spin diffusion (MIRROR-SD) and to establish through-space neighborhood of spins at high MAS frequencies.

The increasing electrification of powertrain systems is driven by the idea of using electric power as an alternative energy source. Fuel cells combined with electric traction are one example. Batteries will have a sufficient energy density for a maximum mileage of 200 km, sufficient for driving even in the largest of conurbations. In urban surroundings, a market for fuel cells as a range extender may develop. For mobility with distances of more than 400 km, there is no real alternative to the internal combustion engine powered by liquid hydrocarbons, as Volkswagen engineers predict.

Due to changing economic, technical and social environments and resulting customer demands, future vehicle drive systems will be required to have lower pollutant emissions and greater efficiency, leading to a CO2 reduction. Combining the advantages of the petrol and diesel combustion processes is a way of achieving these objectives. In the Group Research — Drive Systems of Volkswagen AG, this implementation is referred to as the Combined Combustion System CCS.

Veranderte wirtschaftliche, technische und soziale Rahmenbedingungen, gesellschaftliche Trends und daraus resultierende Kundenwunsche erfordern von zukunftigen Fahrzeugantrieben niedrigere Schadstoff-Emissionen und eine hohere Effizienz, was eine Reduktion des CO2-Ausstoses zur Folge hat. Durch die Kombination der Vorteile des Otto- und Dieselbrennverfahrens sollen diese Ziele erreicht werden. Die technische Umsetzung wird in der Konzernforschung Antriebe der Volkswagen AG als CCS-Brennverfahren bezeichnet.

Animals have evolved adhesive structures on their legs to cling to the substrate during locomotion. Here we characterise the ultrastructure and mechanical properties of adhesive pads in Carausius morosus (Phasmatodea) using atomic force microscopy (AFM) as well as transmission and scanning electron microscopy (TEM, SEM). The smooth adhesive arolium has a soft cuticle consisting of principal rods, which branch into finer fibres near the surface. Indentation experiments showed that the pad material consists of distinct layers with different mechanical properties. The 100-300 nm thick outermost layer consisting of the cuticulin envelope and the epicuticle is extremely soft and resilient (mean effective Young's modulus 12 kPa), while the subjacent procuticle is a much stiffer material (mean effective Young's modulus 625 kPa). AFM contact mode imaging revealed that the cuticle is mechanically anisotropic, which can be explained by its fibrillar inner structure. We propose that the described layered structure of smooth adhesive pads, consisting of materials decreasing in stiffness towards the outer surface, represents a superior design to conform and adhere to substrates with roughnesses at different length scales. This design principle could be easily implemented in technical adhesives, and thus has a potential to inspire biomimetic applications.

Royal Society Open Science 3(2), 150617 (2016). doi:10.1098/rsos.150617, Published by Royal Soc. Publ., London

Spider silk production has been studied intensively in the last years. However, capture threads of cribellate spiders employ an until now often unnoticed alternative of thread production. This thread in general is highly interesting, as it not only involves a controlled arrangement of three types of threads with one being nano-scale fibres (cribellate fibres), but also a special comb-like structure on the metatarsus of the fourth leg (calamistrum) for its production. We found the cribellate fibres organized as a mat, enclosing two parallel larger fibres (axial fibres) and forming the typical puffy structure of cribellate threads. Mat and axial fibres are punctiform connected to each other between two puffs, presumably by the action of the median spinnerets. However, this connection alone does not lead to the typical puffy shape of a cribellate thread. Removing the calamistrum, we found a functional capture thread still being produced, but the puffy shape of the thread was lost. Therefore, the calamistrum is not necessary for the extraction or combination of fibres, but for further processing of the nano-scale cribellate fibres. Using data from Uloborus plumipes we were able to develop a model of the cribellate thread production, probably universally valid for cribellate spiders.

Adhesive organs like arolia of insects allow these animals to climb on different substrates by creating high adhesion forces. According to the Dahlquist criterion, adhesive organs must be very soft exhibiting an effective Young's modulus of below 100 kPa to adhere well to substrates. Such a low effective Young's modulus allows the adhesive organs to make almost direct contact to the substrate and results in van der Waals forces beside capillary forces. In previous studies the effective Young's moduli of adhesive organs were determined using indentation tests yielding their structure to be very soft indeed. However, adhesive organs show a layered structure, thus the measured values comprise the effective Young's moduli of several layers of the adhesive organs. In this study, a new approach is illustrated to measure the Young's modulus of the outermost layer of the arolium, i.e. of the epicuticle, of the stick insect Carausius morosus. As a result of the epicuticle being supported by upright fibres tensile tests allow the determination of the Young's modulus of the epicuticle hardly affected by subjacent layers. In our tensile tests arolia of stick insects adhering on a latex membrane were stretched by stretching the membrane while the elongation of the contact area between an arolium and the membrane was recorded. For analysis mathematical models of the mechanical system were developed. When fed with the observed elongations, these models yield estimates for the Young's modulus of the epicuticle of about a hundred megapascal. Thus in arolia a very thin layer (~225 nm) of a rather stiff material, which is less susceptible to abrasion, makes contact to the substrates while the inner fibrous structure of arolia is responsible for their softness.

Adhesive organs enable insects to cling to various substrates. During locomotion, a very fast but reliable change of adhesion and detachment is realised. To reveal the detailed underlying mechanisms of this impressive performance, we analysed the ultrastructure of adhesive organs of the stick insect C. morosus using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM).

This article reviews the application of operator-based Floquet theory in solid-state NMR. Basic expressions for calculating effective Hamiltonians based on van Vleck perturbation theory are reviewed for problems with a single frequency or multiple incommensurate frequencies. Such a treatment allows calculation of effective Hamiltonians for resonant and non-resonant problems. Examples from literature are given for single-mode to triple-mode Floquet problems, covering a wide range of applications in solid-state NMR under magic-angle spinning and radio-frequency irradiation of a single nucleus or multiple nuclei.

This article reviews the application of operator-based Floquet theory in solid-state NMR. Basic expressions for calculating effective Hamiltonians based on van Vleck perturbation theory are reviewed for problems with a single frequency or multiple incommensurate frequencies. Such a treatment allows calculation of effective Hamiltonians for resonant and non-resonant problems. Examples from literature are given for single-mode to triple-mode Floquet problems, covering a wide range of applications in solid-state NMR under magic-angle spinning and radio-frequency irradiation of a single nucleus or multiple nuclei.

Image-based rendering techniques require capturing an object or scene from many viewpoints. Often, depth maps are used in addition to the original images for rendering new iews for novel viewpoints not coinciding with one of the original camera positions. Due to the high amount of data, efficient compression is necessary. When the data is stored or transmitted, it is not only desirable to compress the image data but also the depth information. In this paper, the case of sequences recorded with a single, hand-held camera is investigated. These sequences are used for unstructured lumigraph rendering. In addition, the case of multi-view video sequences is analyzed. For both cases, depth maps are compressed using H.264/AVC, and the achievable data rates are studied. For the case of unstructured lumigraph rendering, the effect of depth map compression on the quality of rendered images is analyzed in a second step.

We describe a novel approach to generate dynamic pH gradients suited to fractionate or purify samples of biomolecules or particles such as proteins and viruses in tiny volumes. The method combines diffusion and electromigration between micro-scaled channels embedded in hydrogel. For the used geometry and in accordance with numerical calculations the gel-channel system reaches a tuneable, steady-state pH gradient after a few minutes. For quantification of experimentally generated pH-profiles, the concentration independent extinction ratio of phenol red at two wavelengths is used. The proposed electrophoretic flow-cell is simple and flexible since no Immobilines are required to establish the pH gradient.

In diesem Artikel wird eine neue Technik zur Glanzlichtsubstitution vorgestellt. Ausgehend von einer Farbbildsequenz, die mit einer handgefuhrten Kamera aufgezeichnet wird, wird zunachst ein so genanntes Lichtfeld erzeugt. Auserdem wird fur jedes Bild der Sequenz eine Glanzlichtmaske berechnet. Diese wird anschliesend als Vertrauenskarte im Lichtfeld benutzt. Dadurch werden Farbpixel an den markierten Glanzlichtstellen durch Pixel aus anderen Bildern ersetzt, bei denen diese Pixel nicht durch Glanzlichter uberbelichtet waren. Diese Methode erhoht die Bildqualitat. Eine Anwendung des Verfahrens auf endoskopische Bilder und Evaluation auf realen und auf synthetischen Daten beschliest den Beitrag.

A theoretical description of the two-pulse phase-modulated (TPPM) decoupling sequence in magic-angle spinning NMR is presented using a triple-mode Floquet approach. The description is formulated in the radio-frequency interaction-frame representation and is valid over the entire range of possible parameters leading to the well-known results of continuous-wave (cw) decoupling and XiX decoupling in the limit of a phase change of 0 degrees and 180 degrees , respectively. The treatment results in analytical expressions for the heteronuclear residual coupling terms and the homonuclear spin-diffusion terms. It also allows the characterization of all resonance conditions that can contribute in a constructive or a destructive way to the residual linewidth. Some of the important resonance conditions are described for the first time since they are not accessible in previous treatments. The combination of the contributions from the residual couplings and the resonance conditions to the effective Hamiltonian, as obtained in a Floquet description, is shown to be required to describe the decoupling behavior over the full range of parameters. It is shown that for typical spin system and experimental parameters a (13)C linewidth of approximately 12 Hz can be obtained for TPPM decoupling in an organic solid or a protein. This is a major contribution to the experimentally observed linewidths of around 20 Hz and indicates that decoupling techniques are still one of the limiting factors in the achievable linewidths.

Many solid-state NMR experiments exploit interference effects between time dependencies in the system Hamiltonian to design an effective time-independent Hamiltonian with the desired properties. Effective Hamiltonians can be designed such that they contain only selected parts of the full system Hamiltonian while all other parts are averaged to zero. A general theoretical description of such experiments has to accommodate several time-dependent perturbations with incommensurate frequencies. We describe an extension of the analytical operator-based Floquet description of NMR experiments to situations with three incommensurate frequencies. Experiments with three time dependencies are quite common in solid-state NMR. Examples include experiments which combine magic-angle spinning and radio-frequency irradiation on two nuclei or asynchronous multiple-pulse sequences on a single spin species. The Floquet description is general in the sense that the resulting effective Hamiltonians can be calculated without a detailed knowledge of the spin-system Hamiltonian and can be expressed fully as a function of the Fourier components of the time-dependent Hamiltonian. As a prototype experiment we treat the application of two continuous-wave (cw) radio-frequency fields under magic-angle spinning. Experiments that are included in such a description are Hartmann-Hahn cross polarization or rotary-resonance recoupling experiments with simultaneous cw decoupling.