The Bunsen gas solubility coefficient of ethylene as a function of temperature and salinity and its importance for nitrogen fixation assays

The acetylene reduction assay is a common method for assessing nitrogen fixation in a variety of marine and freshwater systems. The method measures ethylene, the product of the conversion of the gas acetylene to its reduced form by nitrogenase. Knowledge of the solubility of ethylene in aqueous solution is crucial to the calculation of nitrogen fixation rates and depends on the temperature and salinity of the assay conditions. Despite the increasing interest in marine nitrogen fixation, no gas solubility (Bunsen) coefficients for ethylene in seawater are published to date. Here, we provide a set of equations and present semiempirically derived Bunsen coefficients for ethylene in water (ranging from 0.069 to 0.226) for a range of temperatures and salinities that are relevant for aquatic nitrogen fixation. We apply these data to nitrogen fixation scenarios at different temperatures and salinities and stress the importance of using accurate Bunsen coefficients in nitrogen fixation assays

Scattering Mechanism in Modulation-Doped Shallow Two-Dimensional Electron Gases

We report on a systematic investigation of the dominant scattering mechanism in shallow two-dimensional electron gases (2DEGs) formed in modulation-doped GaAs/Al_{x}Ga_{1-x}As heterostructures. The power-law exponent of the electron mobility versus density, mu \propto n^{alpha}, is extracted as a function of the 2DEG's depth. When shallower than 130 nm from the surface, the power-law exponent of the 2DEG, as well as the mobility, drops from alpha \simeq 1.65 (130 nm deep) to alpha \simeq 1.3 (60 nm deep). Our results for shallow 2DEGs are consistent with theoretical expectations for scattering by remote dopants, in contrast to the mobility-limiting background charged impurities of deeper heterostructures.Comment: 4 pages, 3 figures, modified version as accepted in AP

VHF discharges in storm cells producing microbursts

An experiment was carried out in which 3-D mapping of VHF sources was compared to a 3-D description of the reflectivity and dynamics of associated cloud cells observed by a radar network. Data from 61 microbursts were analyzed and it was found that, in 93 pct. of the cases, electrical activity precedes outflow development. The results confirm that the peak in intracloud activity precedes the maximum value of the outflow

Subacute encephalopathy and seizures in alcoholics (SESA) presenting with non-convulsive status epilepticus

AbstractSubacute encephalopathy with seizures in chronic alcoholism (SESA) was first described in 1981 by Niedermeyer who reported alcoholic patients presenting with confusion, seizures and focal neurological deficits and is quite distinct from patients presenting with typical alcohol withdrawal seizures. EEG often reveals periodic discharges and spikes, but SESA presenting with non-convulsive status epilepticus has rarely been described.We report a case of SESA with non-convulsive status epilepticus in a patient who was initially suspected of having a typical alcohol withdrawal seizure.A 61 year old woman with a history of chronic alcoholism was admitted at an outside hospital for confusion thought to be secondary to an alcohol withdrawal seizure. She had right hemiparesis and later developed right facial twitching that did not respond to intravenous fosphenytoin and levetiracetam. She was transferred for further management. Upon arrival, lorazepam and fosphenytoin were given and right face clonic movements resolved. However, continuous EEG monitoring revealed ongoing non-convulsive status epilepticus (NCSE). Following treatment with IV valproate and lacosamide, there was resolution of NCSE.SESA is likely an under recognized clinical syndrome that is quite distinct from typical alcohol withdrawal seizures and requires a different diagnostic and management approach. NCSE is likely to account for the encephalopathy and focal neurological deficits seen in patients presenting with the clinical syndrome of SESA. Therefore, a high degree of suspicion is warranted and continuous EEG monitoring is recommended for alcoholic patients with encephalopathy and focal neurological deficits

Survival of Campylobacter spp. on inoculated pork skin or meat.

Campylobacter is one of the main causes of human foodborne bacterial zoonoses due to food consumption in developed countries. Nine to 32% of pig carcasses are contaminated by Campylobacter. The purpose of the study was to improve our knowledge of the survival of implanted campylobacters from the two kinds of pork matrix meat (skin, muscle) during meat cold domestic storage. One hundred and twenty pork skin and 120 skinless chine samples (25 cm2/sample) were inoculated with two C. jejuni and four C. coli strains and stored in closed box at 4 oc for 1, 4, 8, 15 and 22 days. Campylobacter were isolated from sample suspensions after mechanical pummeling and numbered by direct plating. We calculated the shoulder time (ST), the D value (the time for one log decrease} and the R, value (the time to reach 10% of the initial population R, = ST +D). We compared them in a stratified approach according to pork matrix and strain. According to matrixes, mean D, TS and R, value varied significantly between pork skin (4.3 days, 1.3 days, 5.6 days, respectively} and spare rib (7 .2 days, 3.5 days, 10.8 days, respectively}. On spare rib, R1 was higher (16 days) with one C. coli strain (CCV55). Statistical effects between TS and R, value on spare rib and strain were noticed. This study shows that the survival of campylobacters on pork meat is similar to the survival of Campylobacter on poultry meat. Consequently, good hygiene practices are needed to manage the risk of pork Campylobacter contamination and further studies focusing on survival factors may complete this risk analysis on the pork food chain

Formation and transportation of sand-heap in an inclined and vertically vibrated container

We report the experimental findings of formation and motion of heap in granular materials in an inclined and vertically vibrated container. We show experimentally how the transport velocity of heap up container is related to the driving acceleration as well as the driving frequency of exciter. An analogous experiment was performed with a heap-shaped Plexiglas block. We propose that cohesion force resulted from pressure gradient in ambient gas plays a crucial role in enhancing and maintaining a heap, and ratchet effect causes the movement of the heap. An equation which governs the transport velocity of the heap is presented.Comment: 9 pages, 5 figures, submitted to PR

Observation of gravity-capillary wave turbulence

We report the observation of the cross-over between gravity and capillary wave turbulence on the surface of mercury. The probability density functions of the turbulent wave height are found to be asymmetric and thus non Gaussian. The surface wave height displays power-law spectra in both regimes. In the capillary region, the exponent is in fair agreement with weak turbulence theory. In the gravity region, it depends on the forcing parameters. This can be related to the finite size of the container. In addition, the scaling of those spectra with the mean energy flux is found in disagreement with weak turbulence theory for both regimes

BIOASSAY PROCEDURES FOR OIL AND OIL DISPERSANT TOXICITY EVALUATION

Hazards to marine and estuarine fauna associated with offshore drilling of oil and with transport of large quantities of oils via tankers are numerous and understandable. At present, there is a growing body of evidence on adverse effects to these organisms of crude oil (1) (2) (3) (4) (5) (6) (7) (8) (9) and chemical oil counteracting agents or dispersants (5) (6) (9) (10) (11) (12) (13) (14) (15) (16) (17). These effects are well summarized by Smith (18) and by Carthy and Arthur (19). Comparatively few workers have studied the influence of oil-dispersant mixtures of marine life. Studies by Rosenthal and Gunkel (20) and Kuhl and Mann (5) have led them to conclude that crude oils are less toxic than oil-dispersant mixtures. Spooner (9) states that work with dispersants and oil together is important, but the varying toxicities of the oils and their mechanical awkwardness in biological experiments makes it difficult to standardize such work and to compare it with that of others