Ventilation of the abyss in the Atlantic sector of the Southern Ocean.

The Atlantic sector of the Southern Ocean is the world's main production site of Antarctic Bottom Water, a water-mass that is ventilated at the ocean surface before sinking and entraining older water-masses-ultimately replenishing the abyssal global ocean. In recent decades, numerous attempts at estimating the rates of ventilation and overturning of Antarctic Bottom Water in this region have led to a strikingly broad range of results, with water transport-based calculations (8.4-9.

Role of the time dependence of Boltzmann open probability in voltage-gated proton channels.

The modeling and simulation of experimental families of current-time (I-t) curves of dimeric voltage-gated proton channels and of proton-conducting voltage sensing domains (VSDs) with a minimum of free parameters requires the movement of protons to be controlled by the rate of increase of the Boltzmann open probability p over time in passing from the holding to the depolarizing potential. Families of I-t curves of protomers and proton-conducting VSDs can be satisfactorily fitted by the use of a single free parameter expressing the rate constant k for the increase of p over time. Families of I-t curves of dimeric H1 channels can be fitted by a model that assumes an initial proton current I flowing along the two monomeric units, while they are still operating separately; I is gradually replaced by a slower and more potential-dependent current I flowing when the two monomers start operating jointly under the control of the coiled-coil domain.

Controls on the Isotopic Composition of Nitrite (δN and δO) during Denitrification in Freshwater Sediments.

The microbial reduction of nitrate, via nitrite into gaseous di-nitrogen (denitrification) plays a major role in nitrogen removal from aquatic ecosystems. Natural abundance stable isotope measurements can reveal insights into the dynamics of production and consumption of nitrite during denitrification. In this study, batch experiments with environmental bacterial communities were used to investigate variations of concentrations and isotope compositions of both nitrite and nitrate under anoxic conditions.

On the interaction of the highly charged peptides casocidins with biomimetic membranes.

Casocidin I and II (CI and CII) are structurally related antimicrobial peptides made of 39 and 31 amino acids, respectively, which derive from natural proteolytic processing of α-casein and adopt an ordered α-helical structure in biomimetic membranes. Their putative membrane-permeabilizing activity was investigated at Hg-supported self-assembled monolayers (SAMs) and at tethered bilayer lipid membranes (tBLMs); the latter consisted of a monolayer of 2,3,di-O-phytanyl-sn-glycerol-1-tetraethylene-glycol-d,l-α lipoic acid ester thiolipid (DPTL), with a dioleoylphosphatidylcholine (DOPC) or dioleoylphosphatidylserine (DOPS) monolayer on top of it. Interaction of CI and CII with these biomimetic membranes was studied by four electrochemical techniques at pH 3, 5.

Stable isotopes in the atmospheric marine boundary layer water vapour over the Atlantic Ocean, 2012-2015.

The water vapour isotopic composition (HO, HO and HHO) of the Atlantic marine boundary layer has been measured from 5 research vessels between 2012 and 2015. Using laser spectroscopy analysers, measurements have been carried out continuously on samples collected 10-20 meter above sea level. All the datasets have been carefully calibrated against the international VSMOW-SLAP scale following the same protocol to build a homogeneous dataset covering the Atlantic Ocean between 4°S to 63°N.

When and how the melittin ion channel exhibits ohmic behavior.

Melittin exhibits an ohmic behavior in a lipid bilayer having a DOPC distal leaflet and interposed between a 2.25nm tetraethyleneoxy chain tethered to a mercury drop and an aqueous solution. This behavior is induced in a pH6.

A capacitive probe for Electron Spin Resonance detection.

The use of the magnetic field associated with Maxwell displacement current in a capacitor is proposed for the detection of Electron Spin Resonance. A probe based on this concept is realized and successfully tested with CW radio-frequency in the band going from 200MHz to 1GHz with a DPPH sample. A significant increase of Signal to Noise Ratio is observed while increasing the frequency.

Electron-paramagnetic resonance detection with software time locking.

A setup for electron paramagnetic resonance with narrow band digital detection is described. A low frequency reference tone is added to the radio frequency signal. This reference signal, after digital detection, is used to lock the resonance signal, even in the absence of hardware time locking among the radio frequency generator, the conversion local oscillators, and the sampling stage.

Use of scanning probe microscopy to study the evolution of nanometer sized liquid structures.

The evolution of the profile of nanometer sized water drops on a mica surface has been studied through hydration scanning probe microscopy. A time range from a few seconds down to a fraction of millisecond after the formation of the drop has been explored. This high time resolution has been obtained by sampling a series of statistically equivalent drops.

Photoinduced electroreduction of chlorophyllide on alkanethiol-coated mercury.

Monolayers of n-alkanethiols of chain length from C12 to C18 were self-assembled on a hanging mercury drop electrode, and a film of chlorophyllide (Chlide) was adsorbed on top of them. The reduction photocurrents following illumination of the Chlide film were measured over the potential range in which the Chlide is electroinactive in the dark, and their action spectra were determined. Plotting the derivative of the photocurrents with respect to the applied potential against potential yields bell-shaped curves that can be fitted to a Gaussian.

Photoelectric response of purple membrane fragments adsorbed on a lipid monolayer supported by mercury and characterization of the resulting interphase.

Purple membrane (PM) fragments were adsorbed on a dioleoylphosphatidylcholine (DOPC) monolayer supported by mercury to investigate the kinetics of light-driven proton transport by bacteriorhodopsin (bR). PM fragments were also adsorbed on a mercury-supported triethyleneoxythiol (TET) monolayer. On both monolayers, the light-on current exhibits a finite, potential dependent stationary component that decreases linearly with a positive shift in the applied potential.