In-vivo confocal scanning laser microscopy of the cerebral microcirculation

Confocal scanning laser microscopy (CSLM) was used to study the microcirculation of the brain neocortex in anaesthetized rats. After removal of the dura mater, implantation of a closed cranial window, and intravenous injection of fluorescein, three-dimensional reconstructions of cortical capillaries were performed down to a depth of 250 μm below the pial surface. Using a one-dimensional approach (single line scanning), erythrocyte (negative contrast in fluorescently labelled plasma) and leucocyte (labelled with rhodamine 6 G) velocity and supply rate in cortical capillaries were measured. The effect of CO₂-inhalation on capillary blood flow dynamics was studied. Capillaries were imaged continuously for up to 1 h without changes in flow or fluorescence pattern. However, by increasing the laser power 10–100-fold, aggregate formation was induced and capillaries were occluded, possibly due to damage to vascular endothelium. We conclude that CSLM can be used to study morphological and dynamic aspects of fluorescently labelled subsurface structures in organs of experimental animals.     

The Significance of Epithelial-to-Mesenchymal Transition for Circulating Tumor Cells

Epithelial to mesenchymal transition (EMT) is a process involved in embryonic development, but it also plays a role in remote metastasis formation in tumor diseases. During this process cells lose their epithelial features and adopt characteristics of mesenchymal cells. Thereby single tumor cells, which dissolve from the primary tumor, are enabled to invade the blood vessels and travel throughout the body as so called “circulating tumor cells” (CTCs). After leaving the blood stream the reverse process of EMT, the mesenchymal to epithelial transition (MET) helps the cells to seed in different tissues, thereby generating the bud of metastasis formation. As metastasis is the main reason for tumor-associated death, CTCs and the EMT process are in the focus of research in recent years. This review summarizes what was already found out about the molecular mechanisms driving EMT, the consequences of EMT for tumor cell detection, and suitable markers for the detection of CTCs which underwent EMT. The research work done in this field could open new roads towards combating cancer.     

Reconciling fault-tolerant distributed computing and systems-on-chip

Classic distributed computing abstractions do not match well the reality of digital logic gates, which are the elementary building blocks of Systems-on-Chip (SoCs) and other Very Large Scale Integrated (VLSI) circuits: Massively concurrent, continuous computations undermine the concept of sequential processes executing sequences of atomic zero-time computing steps, and very limited computational resources at gate-level make even simple operations prohibitively costly. In this paper, we introduce a modeling and analysis framework based on continuous computations and zero-bit message channels, and employ this framework for the correctness & performance analysis of a distributed fault-tolerant clocking approach for Systems-on-Chip (SoCs). Starting out from a “classic” distributed Byzantine fault-tolerant tick generation algorithm, we show how to adapt it for direct implementation in clockless digital logic, and rigorously prove its correctness and derive analytic expressions for worst case performance metrics like synchronization precision and clock frequency. Rather than on absolute delay values, both the algorithm’s correctness and the achievable synchronization precision depend solely on the ratio of certain path delays. Since these ratios can be mapped directly to placement & routing constraints, there is typically no need for changing the algorithm when migrating to a faster implementation technology and/or when using a slightly different layout in an SoC.     

Thiophene‐ and silarylene‐containing polyesters. Resonance effect on conductivity after polarization in an external electric field

Polyesters were synthesized by direct polycondensation of thiophene‐2,5‐dicarboxylic acid and five different silarylene‐containing diphenols using a tosyl chloride/pyridine/N,N‐dimethylformamide system as a condensing agent. Polymers were obtained in good yields and were characterized using Fourier transform infrared and NMR (¹H, ¹³C, 135‐DEPT and ²⁹Si) spectroscopy and elemental analysis. All polymers were completely soluble in aprotic organic polar solvents such as dimethylformamide, dimethylsulfoxide and N‐methyl‐2‐pyrrolidone. The range of effective mass of the polymers (m/z) was 1 × 10⁵–2 × 10⁵, determined using electrospray ionization mass spectrometry. Asymmetry and steric hindrance prevented dense packing of the polymeric chains, showing glass transition temperatures between ? 78 and ? 51 °C and loss of thermal stability at 177–199 °C (10% weight loss). Additionally, the melting points of the polyesters were found to be in the range 62–67 °C. Because of this, the samples were semi‐solid at room temperature. The optical band gaps of the polymers were observed between 4.54 and 4.48 eV, corresponding in all cases to insulator behavior. The molecular structure of the samples was studied using X‐ray diffraction, showing a degree of order that was associated with two monoclinic lattices. Additionally, the conductivity was studied using a two‐point method with contacts on top of polymer films. Prior to the electrical measurement, the samples were polarized in an external electric field of 0.8 to 6.4 V cm^?1, and the alignment of the dipoles increased the electrical conductivity. Copyright © 2012 Society of Chemical Industry     

Evaluating experience sampling of stress in a single-subject research design

How can we measure subjective experiences or internal states? The rise of happiness as a variable of interest in policy decisions, for instance, necessitates appropriate methods for valid and practical measurements. This self-experimental work contributes to scientific development by analysing and evaluating three methods for recording stress: the experience sampling method with a smartphone, an adapted version of the day reconstruction method (DRM, a diary method) and an ubiquitous biophysical measure of the heart rate. All three methods yield significant treatment effects for eight “natural experiments” as stressors. Surprisingly, the DRM outperforms the other two methods in a simple factor analysis and appears to have no recall bias. Also reactivity has no substantial impact, and an applied researcher should minimise the complexity of the input (amount and type of questions, interface and integration) rather than reduce the number of prompts. Some evidence suggests a Likert-type scale should be preferred over a continuous one. This work also reflects upon the nature of single-subject research and the role of the experimenter.