Evidence for P-Glycoprotein Involvement in Cell Volume Regulation Using Coulter Sizing in Flow Cytometry

The regulation of cell volume is an essential function that is coupled to a variety of physiological processes such as receptor recycling, excitability and contraction, cell proliferation, migration, and programmed cell death. Under stress, cells undergo emergency swelling and respond to such a phenomenon with a regulatory volume decrease (RVD) where they release cellular ions, and other osmolytes as well as a concomitant loss of water. The link between P-glycoprotein, a transmembrane transporter, and cell volume regulation is controversial, and changes in cells volume are measured using microscopy or electrophysiology. For instance, by using the patch-clamp method, our team demonstrated that chloride currents activated in the RVD were more intense and rapid in a breast cancer cell line overexpressing the P-glycoprotein (P-gp). The Cell Lab Quanta SC is a flow cytometry system that simultaneously measures electronic volume, side scatter and three fluorescent colors; altogether this provides unsurpassed population resolution and accurate cell counting. Therefore, here we propose a novel method to follow cellular volume. By using the Coulter-type channel of the cytometer Cell Lab Quanta SC MPL (multi-platform loading), we demonstrated a role for the P-gp during different osmotic treatments, but also a differential activity of the P-gp through the cell cycle. Altogether, our data strongly suggests a role of P-gp in cell volume regulation.     

Characteristic Dependency of Hydrogen-Affected Fatigue Crack Growth and Crack Tip Plasticity on Low Loading Frequency in α-Iron

Metallurgical and Materials Transactions A - Aiming to investigate the dependency of hydrogen-affected fatigue crack growth (HAFCG) on the loading frequency f, this study experimentally...     

Using 3D modeling and remote sensing capabilities for a better understanding of spatio-temporal heterogeneities of phytoplankton abundance in large lakes

Lake biological parameters show important spatio-temporal heterogeneities. This is why explaining the spatial patchiness of phytoplankton abundance has been a recurrent ecological issue and is an essential prerequisite for objectively assessing, protecting and restoring freshwater ecosystems. The drivers of these heterogeneities can be identified by modeling their dynamics. This approach is useful for theoretical and applied limnology. In this study, a 3D hydrodynamic model of Lake Geneva (France/Switzerland) was created. It is based on the Delft3D suite software and includes the main tributary (Rhône River) and two-dimensional high-resolution meteorological forcing. It provides 3D maps of water temperature and current velocities with a 1?h time step on a 1?km horizontal grid size and with a vertical resolution of 1?m near the surface to 7?m at the bottom of the lake. The dynamics and the drivers of phytoplankton heterogeneities were assessed by combining the outputs of the model and chlorophyll-a concentration (Chl-a) data from MERIS satellite images between 2008 and 2012. Results highlight physical mechanisms responsible for the occurrence of seasonal hot-spots in phytoplankton abundance in the lake. At the beginning of spring, Chl-a heterogeneities are usually caused by an earlier onset of phytoplankton growth in the shallowest and more sheltered areas; spatial differences in the timing of phytoplankton growth can be explained by spatial variability in thermal stratification dynamics. In summer, transient and locally higher phytoplankton abundances are observed in relation to the impact of basin-scale upwelling.     

Atmospheric total ozone column evaluation with a smartphone image sensor

A new method for quantifying the total ozone column (TOC) using a smartphone image sensor has been developed and validated. The TOC has been evaluated for relatively cloud free days at high air masses for solar zenith angles between 49.7° and 76.7° at a sub-tropical site. The method is based on the evaluation of the direct solar irradiances at 305 and 312 nm using the red colour pixel values of the solar disc recorded at these wavelengths by a smartphone camera. Narrow bandpass filters of 2 nm full width at half maximum at each of the two wavelengths were used in turn placed over the camera sensor to directly image the solar disc. The calibration of the pixel values of the solar disc to provide the direct solar irradiances at each of these two wavelengths allowed evaluation of the TOC calibrated to a portable sun photometer. The root mean square error (RMSE) for the smartphone-derived ozone values calibrated to corresponding values from a portable sun photometer was 4.3 Dobson Units (DU). The validation measurements for the smartphone-derived ozone values provided an average residual of 3.5% (up to a maximum of 11%) compared to the corresponding portable sun photometer values, with an RMSE of 8.4 DU during days of intermittent inclement weather conditions. The evaluation of the TOC based on a widely available device such as a smartphone has the potential to increase current citizen science initiatives valued by the general public and school-aged learners by enhancing knowledge and awareness of ozone and the resulting influences on the solar ultraviolet environment.     

Decomposition of the acceleration levels distribution of a road transport into a sum of weighted Gaussians: Application to vibration tests

The usual method to simulate vertical vibrations generated by road transport in laboratory is to use the average power spectral density. With this method, the distribution of the acceleration levels throughout the test is a Gaussian which does not conform to the reality of a transport. This study proposes an improvement of the classical method; this improvement permits to simulate the power spectral density and the distribution of acceleration levels by using a conventional device. The main idea of this method is to decompose the distribution of an actual road transport by using a sum of weighted Gaussians. Then, we apply the power spectral density with the root mean square acceleration (g_rms) level and duration corresponding to each Gaussian calculated from the weighted sum. We show that the weighting coefficients correspond to the time fraction of the test. Over the total duration of the test, we then retrieve the acceleration levels distribution of the actual transport. This new test method is experimentally validated with 2 examples of actual transports.     

Bioinspired Stable and Photoluminescent Assemblies for Power Generation

Peptide assemblies are ideal components for eco‐friendly optoelectronic energy harvesting devices due to their intrinsic biocompatibility, ease of fabrication, and flexible functionalization. However, to date, their practical applications have been limited due to the difficulty in obtaining stable, high‐performance devices. Here, it is shown that the tryptophan‐based simplest peptide cyclo‐glycine‐tryptophan (cyclo‐GW) forms mechanically robust (elastic modulus up to 24.0 GPa) and thermally stable up to 370 °C monoclinic crystals, due to a supramolecular packing combining dense parallel β‐sheet hydrogen bonding and herringbone edge‐to‐face aromatic interactions. The directional and extensive driving forces further confer unique optical properties, including aggregation‐induced blue emission and unusual stable photoluminescence. Moreover, the crystals produce a high and sustained open‐circuit voltage (1.2 V) due to a high piezoelectric coefficient of 14.1 pC N^?1. These findings demonstrate the feasibility of utilizing self‐assembling peptides for fabrication of biointegrated microdevices that combine high structural stability, tailored optoelectronics, and significant energy harvesting properties.     

Encoding Information on the Excited State of a Molecular Spin Chain

The quantum states of nano-objects can drive electrical transport properties across lateral and local-probe junctions. This raises the prospect, in a solid-state device, of electrically encoding information at the quantum level using spin-flip excitations between electron spins. However, this electronic state has no defined magnetic orientation and is short-lived. Using a novel vertical nanojunction process, these limitations are overcome and this steady-state capability is experimentally demonstrated in solid-state spintronic devices. The excited quantum state of a spin chain formed by Co phthalocyanine molecules coupled to a ferromagnetic electrode constitutes a distinct magnetic unit endowed with a coercive field. This generates a specific steady-state magnetoresistance trace that is tied to the spin-flip conductance channel, and is opposite in sign to the ground state magnetoresistance term, as expected from spin excitation transition rules. The experimental 5.9 meV thermal energy barrier between the ground and excited spin states is confirmed by density functional theory, in line with macrospin phenomenological modeling of magnetotransport results. This low-voltage control over a spin chain's quantum state and spintronic contribution lay a path for transmitting spin wave-encoded information across molecular layers in devices. It should also stimulate quantum prospects for the antiferromagnetic spintronics and oxides electronics communities.