Standardized microgel beads as elastic cell mechanical probes.

Cell mechanical measurements are gaining increasing interest in biological and biomedical studies. However, there are no standardized calibration particles available that permit the cross-comparison of different measurement techniques operating at different stresses and time-scales. Here we present the rational design, production, and comprehensive characterization of poly-acrylamide (PAAm) microgel beads mimicking size and overall mechanics of biological cells. We produced mono-disperse beads at rates of 20-60 kHz by means of a microfluidic droplet generator, where the pre-gel composition was adjusted to tune the beads' elasticity in the range of cell and tissue relevant mechanical properties. We verified bead homogeneity by optical diffraction tomography and Brillouin microscopy. Consistent elastic behavior of microgel beads at different shear rates was confirmed by AFM-enabled nanoindentation and real-time deformability cytometry (RT-DC). The remaining inherent variability in elastic modulus was rationalized using polymer theory and effectively reduced by sorting based on forward-scattering using conventional flow cytometry. Our results show that PAAm microgel beads can be standardized as mechanical probes, to serve not only for validation and calibration of cell mechanical measurements, but also as cell-scale stress sensors.

Fast stray field computation on tensor grids.

A direct integration algorithm is described to compute the magnetostatic field and energy for given magnetization distributions on not necessarily uniform tensor grids. We use an analytically-based tensor approximation approach for function-related tensors, which reduces calculations to multilinear algebra operations. The algorithm scales with N4/3 for N computational cells used and with N2/3 (sublinear) when magnetization is given in canonical tensor format. In the final section we confirm our theoretical results concerning computing times and accuracy by means of numerical examples.

Synthesis and supramolecular characterization of a novel class of glycopyranosyl-containing amphiphiles.

A novel class of glycopeptidolipids is described, which potentially can be used as a novel antigen-delivery system. The compounds have been prepared by a combination of solid-supported and solution-based methods. The use of the orthogonally protected FmocLysDde derivative provided an opportunity to incorporate two different types lipids. It was found that the model compound 1 forms aggregates in aqueous media which can be described as rod or tubelike structures. The aggregates can be stabilized by topotactic photopolymerization. Studies on the structural analogues 2-5 revealed the effect of the carbohydrate, peptide, and lipid moiety on the aggregation properties. It is concluded that none of the structure elements can lay claim to be exclusively important for the formation of highly organized aggregates such as tubes, fibers, or helical ribbons from 1, but the presence of all of these structural elements afforded the most uniformly shaped extended structures.

Visual discrimination of local surface depth and orientation.

Many theoretical analyses of 3-dimensional form perception assume that visible surfaces in the environment are perceptually represented in terms of local mappings of metric depth and/or orientation. Although this approach is often taken for granted in the study of human vision, there have been relatively few attempts to demonstrate its psychological validity empirically. In an effort to shed new light on this issue, our research has been designed to investigate the accuracy with which observers can discriminate metric depth and orientation intervals on smoothly curved surfaces. Observers were presented with visual images of surfaces defined by shading and/or texture, on which two pairs of points were designated with small dots. In Experiment 1, their task was to identify which pair of points had a greater difference in depth; in Experiment 2 they were required to judge which pair had a greater difference in orientation. The Weber fractions obtained for these tasks were 10 to 100 times greater than those that have been reported for other types of sensory discrimination, indicating that the perception of metric structure from these displays is surprisingly coarse grained.

Perceived depth inversion of smoothly curved surfaces due to image orientation.

A relative depth judgement task was used to distinguish perceived reversals in depth due to image orientation from spontaneous reversals such as those observed with a Necker cube. Results demonstrate that inversion effects due to image orientation can occur for several different types of pictorial representation and that many of these effects are incompatible with traditional explanations involving a perceptual bias for overhead illumination. When this bias was neutralized by placing the light source at the point of observation, the effects of image orientation were just as large as with overhead illumination. Similar results were also obtained for surfaces depicted with texture or motion in which all relevant shading information was eliminated. These results can be explained by a perceptual bias for backward slanting surfaces, but additional evidence suggests that this bias can be attenuated by the presence of smooth occlusion contours.

Visual perception of smoothly curved surfaces from double-projected contour patterns.

This research was designed to examine how human observers are able to perceive the 3-dimensional structure of smoothly curved surfaces from projected patterns of surface contours. Displays were generated by using a method of double projection that made it possible to cover a surface with a wide range of contour patterns of varying geometric structure and to eliminate systematic variations of image shading. The compelling impression of 3-dimensional form from these patterns provides strong evidence that the ability of observers to perceptually interpret surface contours is considerably less restrictive than would be reasonable to expect on the basis of existing computational models. Results suggest that the perceptual analysis of surface contours is able to exploit statistical regularities of contour structure over appropriately large regions of visual space.

Ordinal structure in the visual perception and cognition of smoothly curved surfaces.

In theoretical analyses of visual form perception, it is often assumed that the 3-dimensional structures of smoothly curved surfaces are perceptually represented as point-by-point mappings of metric depth and/or orientation relative to the observer. This article describes an alternative theory in which it is argued that our visual knowledge of smoothly curved surfaces can also be defined in terms of local, nonmetric order relations. A fundamental prediction of this analysis is that relative depth judgments between any two surface regions should be dramatically influenced by monotonicity of depth change (or lack of it) along the intervening portions of the surface through which they are separated. This prediction is confirmed in a series of experiments using surfaces depicted with either shading or texture. Additional experiments are reported, moreover, that demonstrate that smooth occlusion contours are a primary source of information about the ordinal structure of a surface and that the depth extrema in between contours can be optically specified by differences in luminance at the points of occlusion.

[Valgus osteotomies preceding total endoprosthesis]. / Valgisierende Osteotomien im Vorfeld der Totalendoprothese (TEP).

A progress report is presented in this paper on 172 follow-up checks of cases with valgus osteotomy of the hip. Patients aged between 25 and 45 years with advanced coxarthrosis and severe deformations of the hip joint were predominant on the list. Valgus osteotomy, using surgical techniques according to Pauwels and Bombelli, proved successful under these conditions in 85 per cent of all cases. Those good results were reflected in lasting reduction of pain and maintenance of adequate articular functionality. Bridging of the time gap up to endoprosthetic replacement at age levels of 50 or 60 years has been considered another benefit of the method. There were no severe complications. The failure rate was clearly increased among patients with overweight.

[Therapeutic use of synthetic Gn-RH-Dirigestran in disorders of the reproductive cycle in cows from low-fertility herds]. / Terapeutické pouzití syntetického Gn-RH-Dirigestranu pri poruchách reprodukcního cyklu krav v chovech s nízkou plodností.

Synthetic Gn-RH-Dirigestran Spofa was used for the treatment of 121 cows with functional ovarial disorders. Out of this total number, 41 cows showed no postpartal and no post-service symptoms of oestrus, 59 returned to oestrus with irregular cycles, and 21 cows showed an irregular course of oestrus. The treatment was made in herds with a low conception rate (32-37% conceptions after the first insemination, service period 108 to 142 days). On the whole, 80.1% of the treated cows got in calf, 53.7% conceived after the first insemination. The average time from treatment to successful insemination was 39 days. The treatment was started 148 days from parturition, on an average. The average insemination index of the treated cows was 1.44. As to cows out of heat, 70.7% got in calf on the whole and 51.2% after the first insemination, the therapeutic service period (TSP) being 44 days. Out of the cows returning to oestrus with an irregular cycle, 84.7% got in calf and 52.5% got in calf after the first insemination with the TSP of 37 days, and the cows with irregular cycle the conception was recorded in 85.7% (61.9% after the first insemination with the average TSP of 35 days). On the whole, 82% of treated cows showed clearly visible symptoms of oestrus after the application of Dirigestran. The pregnancy of the whole set (121 treated cows) was higher by 15 to 21% after the first insemination and by 41 to 49% after all inseminations, as compared with the pregnancy of normally inseminated cows in these herds. The results show that the treatment of the functional disorders of ovaries is also practicable in cows in herds with a decreased fertility if this treatment is not impaired by spermiotoxicity or embryotoxicity owing to the effects of inadequate secretions of sexual organs caused by incorrect nutrition or infections.