Oxygen exchange and ice melt measured at the ice-water interface by eddy correlation

This study examined fluxes across the ice-water interface utilizing the eddy correlation technique. Temperature eddy correlation systems were used to determine rates of ice melting and freezing, and O<sub>2</sub> eddy correlation systems were used to examine O<sub>2</sub> exchange rates driven by biological and physical processes. The study was conducted below 0.7 m thick sea-ice in mid-March 2010 in a southwest Greenland fjord and revealed low rates of ice melt at a maximum of 0.80 mm d<sup>−1</sup>. The O<sub>2</sub> flux associated with release of O<sub>2</sub> depleted melt water was less than 13 % of the average daily O<sub>2</sub> respiration rate. Ice melt and insufficient vertical turbulent mixing due to low current velocities caused periodic stratification immediately below the ice. This prevented the determination of fluxes 61 % of the deployment time. These time intervals were identified by examining the velocity and the linearity and stability of the cumulative flux. The examination of unstratified conditions through vertical velocity and O<sub>2</sub> spectra and their cospectra revealed characteristic fingerprints of well-developed turbulence. From the measured O<sub>2</sub> fluxes a photosynthesis/irradiance curve was established by least-squares fitting. This relation showed that light limitation of net photosynthesis began at 4.2 μmol photons m<sup>−2</sup> s<sup>−1</sup>, and that algal communities were well-adapted to low-light conditions as they were light saturated for 75 % of the day during this early spring period. However, the sea-ice associated microbial and algal community was net heterotrophic with a daily gross primary production of 0.69 mmol O<sub>2</sub> m<sup>−2</sup> d<sup>−1</sup> and a respiration rate of −2.13 mmol O<sub>2</sub> m<sup>−2</sup> d<sup>−1</sup> leading to a net ecosystem metabolism of −1.45 mmol O<sub>2</sub> m<sup>−2</sup> d<sup>−1</sup>. This application of the eddy correlation technique produced high temporal resolution O<sub>2</sub> fluxes and ice melt rates that were measured without disturbing the in situ environmental conditions while integrating over an area of approximately 50 m<sup>2</sup> which incorporated the highly variable activity and spatial distributions of sea-ice communities

Side effects of extra tRNA supplied in a typical bacterial protein production scenario

Recombinant protein production is at the core of biotechnology and numerous molecular tools and bacterial strains have been developed to make the process more efficient. One commonly used generic solution is to supply extra copies of low‐abundance tRNAs to compensate for the presence of complementary rare codons in genes‐of‐interest. Here we show that such extra tRNA, supplied by the commonly used pLysSRARE2 plasmid, can cause two side effects: (1) growth and gene expression can be impaired, and (2) apparent positive effects can be caused by differential expression of the lysozyme gene encoded on the same plasmid and not the tRNAs per se. These phenomena seem to have been largely overlooked despite the huge popularity of the T7/pET‐based systems for bacterial protein production

Diabetes is associated with impaired myocardial performance in patients without significant coronary artery disease

<p>Abstract</p> <p>Background</p> <p>Patients with diabetes mellitus (DM) have high risk of heart failure. Whether some of the risk is directly linked to metabolic derangements in the myocardium or whether the risk is primarily caused by coronary artery disease (CAD) and hypertension is incompletely understood. Echocardiographic tissue Doppler imaging was therefore performed in DM patients without significant CAD to examine whether DM per se influenced cardiac function.</p> <p>Methods</p> <p>Patients with a left ventricular (LV) ejection fraction (EF) > 35% and without significant CAD, prior myocardial infarction, cardiac pacemaker, atrial fibrillation, or significant valve disease were identified from a tertiary invasive center register. DM patients were matched with controls on age, gender and presence of hypertension.</p> <p>Results</p> <p>In total 31 patients with diabetes and 31 controls were included. Mean age was 58 ± 12 years, mean LVEF was 51 ± 7%, and 48% were women. No significant differences were found in LVEF, left atrial end systolic volume, or left ventricular dimensions. The global longitudinal strain was significantly reduced in patients with DM (15.9 ± 2.9 vs. 17.7 ± 2.9, p = 0.03), as were peak longitudinal systolic (S') and early diastolic (E') velocities (5.7 ± 1.1 vs. 6.4 ± 1.1 cm/s, p = 0.02 and 6.1 ± 1.7 vs. 7.7 ± 2.0 cm/s, p = 0.002). In multivariable regression analyses, DM remained significantly associated with impairments of S' and E', respectively.</p> <p>Conclusion</p> <p>In patients without significant CAD, DM is associated with an impaired systolic longitudinal LV function and global diastolic dysfunction. These abnormalities are likely to be markers of adverse prognosis.</p