On the feasibility of using cryo‐treatment as a tool to enhance the abrasive wear behaviour of solid‐lubricated polymeric composites

Cryo‐treatment, a bulk modification technique, is fast emerging as a way with which to improve the wear resistance of metals. This technique has also shown the ability to enhance significantly the abrasive wear performance of some polymers and their short glass‐fibre reinforced composites. In this work, short carbon‐fibre reinforced composites of some heat resistant polymers, such as polyetherimide, polyethersulphone, polyamide 6,6, polyetheretherketone, and polytetrafluoroethylene, were selected to explore the potential of cryo‐treatment. The selected materials were cryogenically treated by cooling them to the temperature of liquid nitrogen. The abrasive wear tests were carried out at ambient temperature in single pass conditions at various loads, on a pin‐on‐disc machine, using silicon carbide paper as a counterface. The investigations revealed that this technique has definite potential to increase the wear performance of carbon‐fibre reinforced composites. An increase in hardness due to cryo‐treatment was thought to be responsible for an observed improvement in wear performance. However, the extent of improvement in the wear performance was not matched by an increase in the hardness value. Scanning electron microscopy proved useful in examining the morphological changes in the composites due to cryo‐treatment.     

Two‐photon laser scanning microscopy as a useful tool for imaging and evaluating macrophage‐, IL‐4 activated macrophage‐ and osteoclast‐based In Vitro degradation of beta‐tricalcium phosphate bone substitute material

Two‐photon microscopy is an innovative technology that has high potential to combine the examination of soft and hard tissues in vitro and in vivo. Calcium phosphates are widely used substitutes for bone tissue engineering, since they are degradable and consequently replaced by newly formed tissue. It is well known that osteoclasts are responsible for the resorption processes during bone remodelling. We hypothesize that also macrophages are actively involved in the resorption process of calcium phosphate scaffolds and addressed this question in in vitro culture systems by two‐photon laser scanning microscopy. Beta‐tricalcium phosphate specimens were incubated with (1) macrophages, (2) interleukin‐4 activated macrophages, and (3) osteoclasts for up to 21 days. Interestingly, macrophages degraded beta‐tricalcium phosphate specimens in an equivalent fashion compared to osteoclasts and significantly more than IL‐4 activated macrophages. An average of ～32% of the macrophages was partially filled with ceramic material while this was 18% for osteoclasts and 9% for IL‐4 activated macrophages. For the first time by applying two‐photon microscopy, our studies show the previously unrecognized potential of macrophages to phagocytose ceramic material, which is expected to have implication on osteoconductive scaffold design. Microsc. Res. Tech. 77:143–152, 2014. © 2013 Wiley Periodicals, Inc.     

Confocal microscopy as a tool for the study of the intranuclear topography of chromosomes

A scanning confocal microscope was used to investigate the spatial positions of specific regions within blood cell nuclei. These centromeric regions were fluorescently labelled by in-situ hybridization to suspended nuclei with a centromere-1-specific DNA probe. The 3-D image data sets, obtained by optical sectioning of the cells, were used to determine the spatial position of the centromeric regions in the nuclei by means of specially developed software. The centromeres were found to be localized near the nuclear boundary. This spatial pattern was tested against a random distribution model by means of the Kolmogorov—Smirnov test. The difference between the two patterns was at a P < 0?01 significance level.     

In vivo second‐harmonic generation and ex vivo coherent anti‐stokes raman scattering microscopy to study the effect of obesity to fibroblast cell function using an Yb‐fiber laser‐based CARS extension unit

Nonlinear microscopy techniques are being increasingly used to perform in vivo studies in dermatology. These methods enable us to investigate the morphology and monitor the physiological process in the skin by the use of femtosecond lasers operating in the red, near‐infrared spectral range (680–1,300 nm). In this work we used two different techniques that require no labeling: second harmonic generation (SHG) for collagen detection and coherent anti‐Stokes Raman scattering (CARS) to assess lipid distribution in genetically obese murine skin. Obesity is one of the most serious public health problems due to its high and increasing prevalence and the associated risk of type 2 diabetes and cardiovascular diseases. Other than these diseases, nearly half of patients with diabetes mellitus suffer from dermatological complications such as delayed wound healing, foot ulcers and several other skin changes. In our experiment we investigated and followed the effects of obesity on dermal collagen alterations and adipocyte enlargement using a technique not reported in the literature so far. Our results indicate that the in vivo SHG and ex vivo CARS imaging technique might be an important tool for diagnosis of diabetes‐related skin disorders in the near future. Microsc. Res. Tech. 78:823–830, 2015. © 2015 Wiley Periodicals, Inc.     

Backscattered electron image of osmium‐impregnated/macerated tissues as a novel technique for identifying the cis‐face of the Golgi apparatus by high‐resolution scanning electron microscopy

The osmium maceration method with scanning electron microscopy (SEM) enabled to demonstrate directly the three‐dimensional (3D) structure of membranous cell organelles. However, the polarity of the Golgi apparatus (that is, the cis–trans axis) can hardly be determined by SEM alone, because there is no appropriate immunocytochemical method for specific labelling of its cis‐ or trans‐faces. In the present study, we used the osmium impregnation method, which forms deposits of reduced osmium exclusively in the cis‐Golgi elements, for preparation of specimens for SEM. The newly developed procedure combining osmium impregnation with subsequent osmium maceration specifically visualised the cis‐elements of the Golgi apparatus, with osmium deposits that were clearly detected by backscattered electron‐mode SEM. Prolonged osmication by osmium impregnation (2% OsO₄ solution at 40°C for 40 h) and osmium maceration (0.1% OsO₄ solution at 20°C for 24 h) did not significantly impair the 3D ultrastructure of the membranous cell organelles, including the Golgi apparatus. This novel preparation method enabled us to determine the polarity of the Golgi apparatus with enough information about the surrounding 3D ultrastructure by SEM, and will contribute to our understanding of the global organisation of the entire Golgi apparatus in various differentiated cells.     

Epifluorescence microscopy study of a quadruple node of triple junctions of grain boundaries in a Eu2+‐doped Kcl:Kbr solid solution by using the doping ion as a fluorochrome

A typical quadruple node (QN) of triple junctions (TJs) of grain boundaries (GBs) in a Eu²⁺‐doped KCl_0.52Br_0.48 solid solution is investigated from the geometrical point of view by epifluorescence microscopy using the doping ion as a fluorochrome. The excitation and fluorescence optical properties of the fluorochrome were previously characterised by spectrophotometry whereas the structural nature of the studied material as well as its Bravais lattice type, unit cell size and long‐range translational order degree was determined by X‐ray diffraction. A three‐dimensional reconstruction was built from the microscopy images of different optical cross‐sections of the studied arrangement of crystal defects. In the close vicinity of the QN, the studied arrangement of crystal defects adopts the geometry of a collapsed tristetrahedron which, centred at the QN, has its legs along the TJs and, hence, has its faces as collapsed in pairs into the GBs. The angles defined by different TJ couples as well as the dihedral angles defined by the different GB couples meeting in every TJ were measured at the QN site. All, the image recording and stacking as well as the measuring procedures are carefully described. The measured TJ angles (97°, 117°, 95°, 117°, 99° and 130° ± 2°) depart from the characteristic angle (109.47°) of a tetrahedron whereas the measured GB angles (101°, 119°, 140°; 125°, 127°, 108°; 133°, 109°, 119°; 129°, 99° and 132° ± 2°) depart from the angular argument (120°) of a 3‐fold symmetry rotation indicating that, in the close neighbourhood of the QN, the studied arrangement of crystal defects is structurally unstable. Such an instability is associated with an observed mismatch in orientation (by angles of 20°, 15°, 33° and 30° ± 2°) between the TJs and some <111> zone axis matrix lattice crystallographic directions ([], [11], [11] and [11]), respectively). Local variations in anionic composition, existing within the solid solution matrix, are discussed to be responsible for this mismatching and, therefore, for the observed structural instability.