The functional role of cardiac T-tubules explored in a model of rat ventricular myocytes

The morphology of the cardiac transverse-axial tubular system (TATS) has been known for decades, but its function has received little attention. To explore the possible role of this system in the physiological modulation of electrical and contractile activity, we have developed a mathematical model of rat ventricular cardiomyocytes in which the TATS is described as a single compartment. The geometrical characteristics of the TATS, the biophysical characteristics of ion transporters and their distribution between surface and tubular membranes were based on available experimental data. Biophysically realistic values of mean access resistance to the tubular lumen and time constants for ion exchange with the bulk extracellular solution were included. The fraction of membrane in the TATS was set to 56%. The action potentials initiated in current-clamp mode are accompanied by transient K+ accumulation and transient Ca2+ depletion in the TATS lumen. The amplitude of these changes relative to external ion concentrations was studied at steady-state stimulation frequencies of 1-5 Hz. Ca2+ depletion increased from 7 to 13.1% with stimulation frequency, while K+ accumulation decreased from 4.1 to 2.7%. These ionic changes (particularly Ca2+ depletion) implicated significant decrease of intracellular Ca2+ load at frequencies natural for rat heart.     

Investigation of the mixing efficiency of a chaotic micromixer using thermal lens spectrometry

This work investigates the efficiency of a chaotic micromixer using thermal lens spectrometry. The outlet of the mixing device was connected to a thermal lens detection head integrating the probe beam optical fibers and the sample capillary. The chaotic micromixer consisted of a Y-shaped poly(dimethylsiloxane) (PDMS) microchip in which ribbed herringbone microstructures were etched on the floor of the main channel. Due to the solvent composition dependence of the thermal lens response, the photothermal method was shown to be highly sensitive to nonhomogeneous mixing compared to fluorescence detection. The apparatus was applied to the determination of Fe2+ with 1,10-phenanthroline using flow injection analysis; a limit of detection of 11 microg L(-1) of iron was obtained.     

Effect of moist or dry heat cooking procedures on carotenoid retention and colour of fillets of rainbow trout (Oncorhynchus mykiss) fed astaxanthin or canthaxanthin

Rainbow trout were pigmented with diets containing astaxanthin or canthaxanthin for 100 days, and then they were moist or dry heat-cooked. Fish fillet weight, fillet colour, and fillet biochemical contents (moisture, canthaxanthin and astaxanthin contents, and total lipid content) were analyzed. There was no significant effect of using astaxanthin or canthaxanthin on moisture, lipid or carotenoid contents of fish fillet. Giving astaxanthin or canthaxanthin to fish resulted in different hues; astaxanthin-fed fish yielded fillets that were visually more red than those of canthaxanthin-fed fish. The dry heat-cooking procedure showed the highest impact on the fillet colour. Carotenoid retention was affected by carotenoid source and cooking procedure. Canthaxanthin appeared more stable after heat processing than did astaxanthin.     

Experimental Investigations on Condensation in the Framework of ENhanced COndensers in Microgravity (ENCOM-2) Project

We report preliminary results on experimental investigations on condensation in the framework of the European Space Agency funded programme Enhanced Condensers in Microgravity (ENCOM-2) which aims at better understanding underlying phenomena during condensation. The first experiment is a study on condensation of HFE on external curvilinear surface of 15 mm height during reduced gravity experiments. It is found that the local minimum of the film thickness exists at the conjugation area of condensed film and the meniscus at the bottom of the fin; this leads to the local maximum of the heat transfer coefficient, which we also found moves towards the fin tip. The second experiment is a study of falling films hydrodynamics inside a vertical long pipe. In particular, characteristics of wavy falling films produced employing intermittent liquid feed are examined in order to assess wave effects on film condensation. Preliminary results suggest that intermittent feed simply divides the film in two autonomous regions with the wave feature of each one depending only on its flow rate. The processing of registered film thickness data can lead to the estimation of the transverse velocity profile in the film, which is mainly responsible for heat transfer during condensation. The third experiment looks at in-tube convective condensation at low mass fluxes (typical of Loop Heat Pipes and Capillary Pumped Loops) of n-pentane inside a 0.56 mm diameter channel. The results show that the mean heat transfer in the annular zone when it is elongated may be less than the mean heat transfer when it is shorter, due to the interface deformation involved by surface tension effect. When the length of this annular zone reaches a critical value, the interface becomes unstable, and a liquid bridge forms, involving the release of a bubble. The heat transfer due to the phase-change in this isolated bubble zone appears to be very small compared to the sensible heat transfer: the bubbles evolve and collapse in a highly subcooled liquid. The last experiment concerns in-tube condensation of R134a inside a square channel of 1.23 mm hydraulic diameter at mass fluxes of 135 kg m^?2 s^?1 and 390 kg m^?2 s^?1 for three different configurations: horizontal, vertical downflow and vertical upflow. For the calculated heat transfer coefficient it is found that gravity has no effect on condensation in downflow configurations at 390 kg m^?2 s^?1 and in upflow conditions at both values of mass velocity. The effect of gravity on the condensation heat transfer coefficient becomes noteworthy in downflow at mass velocity G = 135 kg m^?2 s^?1 and vapour quality lower than 0.6.     

Organic Conjugated Trimers with Donor–Acceptor–Donor Structures for Photocatalytic Hydrogen Generation Application

Organic donor–acceptor–donor (D–A–D) polymers or small molecules are widely investigated in organic solar cells due to their broad light absorption, narrow band gap, excellent charge mobility, and exciton seperation at the interface. However, studies of conjugated small molecules with D–A–D molecule structures as photocatalytically active materials are still rare. In this study, an unprecedented demonstration that photocatalytic activity can in fact be affected by tuning the D and A is given. Especially, the EBE trimer, comprising 3,4-ethylenedioxythiophene (E) and benzothiadiazole (B) units, exhibits the best photophysical, chemical, and photocatalytic properties compared to other D–A–D combinations of D and A. Detailed kinetic studies show that all trimers in organic solution present relatively long-lived and highly emissive photogenerated singlet excitons (τ = 4–13 ns; ϕ_em = 0.5–0.9) as judged by photoluminescence and transient absorption measurements, while in specific cases formation of long-lived triplet states can be identified. Organic microparticles of the trimers are efficiently formed in aqueous solution by nanoprecipitation, and rapid photoinduced electron release/injection to the solvent is evidenced spectroscopically. The results indicate that organic small molecule structures with D–A–D structures pave a new pathway for photocatalytic solar-to-chemical energy conversion of novel small organic molecules.     

Direct Visualization of Chemically Resolved Multilayered Domains in Mixed-Linker Metal–Organic Frameworks

The modular synthesis approach for assembling inorganic nodes and organic multidentate linkers into reticular solids enables rational engineering in porous materials known as metal–organic frameworks (MOFs). Incorporation of two or more linker types in MOF crystals holds great potential for engineering complex pore functionalities, by virtue of chemically heterogeneous domains. However, deciphering linkers distributions in MOFs crystals is challenging because of the insufficient spatial resolution of conventional, chemically sensitive techniques hinders the verification of rational design. Herein, the high spatial resolution and chemical specificity of infrared nanoscopy is leveraged in combination with high-throughput diffraction-limited hyperspectral photoluminescence imaging to determine the composition of individual multivariate UiO-68 MOF crystals (UiO, Universitetet-i-Oslo), after linker-exchange with optically active tetrazine units. The results reveal that the crystals display a three-layer onion-like structure composed of a core-rich in the parent linker, an intermediate multivariate layer with a gradient in linker composition and a proto-MOF external shell. In this outer layer, a fraction of the linkers’ binding groups is hydrogen bonded rather than coordinated with metal nodes, suggestive of superficial reconstruction during the linker-exchange. This study advances the analytical capabilities for studying and engineering heterogeneous domains in mixed-linker MOF crystals down to the nanoscale.