Charging of ice-vapor interfaces

International audienceThe time resolved chemical composition of aerosol particles, formed by the oxidation of alpha-pinene has been investigated by liquid chromatography/mass spectrometry (LC-MS) using negative and positive ionisation methods (ESI(-) and APCI(+)). The experiments were performed at the EUPHORE facility in Valencia (Spain) under various experimental conditions, including dark ozone reactions, photosmog experiments with low NOx mixing ratios and reaction with OH radicals in the absence of NOx (H2O2-photolysis). Particles were sampled on PTFE filters at different stages of the reaction and extracted with methanol. The predominant products from alpha-pinene in the particulate phase are cis-pinic acid, cis-pinonic acid and hydroxy-pinonic acid isomers. Another major compound with molecular weight 172 was detected, possibly a hydroxy-carboxylic acid. These major compounds account for 50% to 80% of the identified aerosol products, depending on the time of sampling and type of experiment. In addition, more than 20 different products have been detected and structures have been tentatively assigned based on their molecular weight and responses to the different ionisation modes. The different experiments performed showed that the aerosol formation is mainly caused by the ozonolysis reaction. The highest aerosol yields were observed in the dark ozone experiments, for which also the highest ratios of mass of identified products to the formed aerosol mass were found (30% to 50%, assuming a density of 1 g cm-3)

Swelling and shrinking kinetics of a lamellar gel phase

We investigate the swelling and shrinking of L_beta lamellar gel phases composed of surfactant and fatty alcohol after contact with aqueous poly(ethylene-glycol) solutions. The height change $\Delta h(t)$ is diffusion-like with a swelling coefficient, S: $\Delta h = S \sqrt{t}$. On increasing polymer concentration we observe sequentially slower swelling, absence of swelling, and finally shrinking of the lamellar phase. This behavior is summarized in a non-equilibrium diagram and the composition dependence of S quantitatively described by a generic model. We find a diffusion coefficient, the only free parameter, consistent with previous measurements.Comment: 3 pages, 4 figures to appear in Applied Physics Letter

Slow hopping and spin dephasing of coulombically bound polaron pairs in an organic semiconductor at room temperature

pre-printPolaron pairs are intermediate electronic states that are integral to the optoelectronic conversion process in organic semiconductors. Here, we report on electrically detected spin echoes arising from direct quantum control of polaron pair spins in an organic light-emitting diode at room temperature. This approach reveals phase coherence on a microsecond time scale, and offers a direct way to probe charge recombination and dissociation processes in organic devices, revealing temperature-independent intermolecular carrier hopping on slow time scales. In addition, the long spin phase coherence time at room temperature is of potential interest for developing quantum-enhanced sensors and information processing systems which operate at room temperature

Phase and micromotion of Bose-Einstein condensates in a time-averaged ring trap

Rapidly scanning magnetic and optical dipole traps have been widely utilised to form time-averaged potentials for ultracold quantum gas experiments. Here we theoretically and experimentally characterise the dynamic properties of Bose-Einstein condensates in ring-shaped potentials that are formed by scanning an optical dipole beam in a circular trajectory. We find that unidirectional scanning leads to a non-trivial phase profile of the condensate that can be approximated analytically using the concept of phase imprinting. While the phase profile is not accessible through in-trap imaging, time-of-flight expansion manifests clear density signatures of an in-trap phase step in the condensate, coincident with the instantaneous position of the scanning beam. The phase step remains significant even when scanning the beam at frequencies two orders of magnitude larger than the characteristic frequency of the trap. We map out the phase and density properties of the condensate in the scanning trap, both experimentally and using numerical simulations, and find excellent agreement. Furthermore, we demonstrate that bidirectional scanning eliminated the phase gradient, rendering the system more suitable for coherent matter wave interferometry.Comment: 10 pages, 7 figure

Application Uniformity of an Impellicone Anhydrous Ammonia Manifold

Since the 1960\u27s anhydrous ammonia (NH) has become the most widely used source of nitrogen (N) fertilizer in agriculture. In fact over 8.1 billion pounds of NH3 is used in the United States every year (Terry and Kirby, 1997). With the cost and wide spread use of NH3 operators are seeking ways to improve uniformity and reduce rates of application. This is because most NH3 tends to be over-applied due to variability in NH3 equipment. Reducing variability will put more money into producers\u27 pockets and reduce the likelihood of N leaching into water supplies. At a cost of $267/ton of NH3, improved application equipment that reduced use in the United States by 5$65 million annually for crop producers (Hanna et al., 2002). A key component of NH3 application equipment that affects uniformity is the distribution manifold. Tests have shown that some outlets on manifolds release two to four times as much NH3 as other outlets. Some knives could be putting on two to four times the desired rate while other knives could be putting on very little NH3 (Fee, 1999). This means that some plants may be getting more N than they can use and others are not getting enough N due to poor distribution by application equipment. In recent years, new manifolds have been tested and produced that improve uniformity among distribution ports

Velocity production in elite BMX riders: a field based study using a SRM power meter

The aim of this study was to analyze the production of velocity in bicycle motocross (BMX) compared to other cycling disciplines. Six elite BMX riders, 5 males and 1 female who competed and trained regularly for a period of 12 yrs ± 2 agreed to take part in this study. Each rider performed 3, 50-m sprint tests and a single 200 m fatigue test. The riders’ peak power, fatigue index, power to weight ratio, and cycling revolution per minute were analyzed using a Schoberer Rad Messtechnik (SRM) BMX power meter. The BMX riders’ peak power and power to weight ratio were all found to be similar to those in other sprint cycling events. Peak power outputs of 1539 ± 148 W and 1030 W were recorded with mean power to weight ratios of 21.29 ± 0.84 W·kg-1 and 16.65 W·kg-1 . The BMX riders’ power fatigue index was found to be higher than other sprint events as riders fatigued at a greater rate. Mean fatigue index was 61.19 ± 5.97 W·sec-1 for the male riders and 53.04 W·sec-1 for the female rider. A notable finding of this study was the relationship of cycling cadence (rev·min-1 ), peak power (Watts) and velocity (mi·h-1 ). This relationship suggests once a BMX rider achieves peak power their pedaling cadence becomes the major contributory factor to velocity production.N/