A holographic system for subsea recording and analysis of plankton and other marine particles

We report here details of the design, development, initial testing and field-deployment of the HOLOMAR system for in-situ subsea holography and analysis of marine plankton and nonliving particles. HOLOMAR comprises a submersible holographic camera ("HoloCam") able to record in-line and off-axis holograms at depths down to 100 m, together with specialised reconstruction hardware ("HoloScan") linked to custom image processing and classification software. The HoloCam consists of a laser and power supply, holographic recording optics and holographic plate holders, a water-tight housing and a support frame. It utilises two basic holographic geometries, in-line and off-axis such that a wide range of species, sizes and concentrations can be recorded. After holograms have been recorded and processed they are reconstructed in full three-dimensional detail in air in a dedicated replay facility. A computer-controlled microscope, using video cameras to record the image at a given depth, is used to digitise the scene. Specially written software extracts a binarised image of an object in its true focal plane and is classified using a neural network. The HoloCam was deployed on two separate cruises in a Scottish sea loch (Loch Etive) to a depth of 100 m and over 300 holograms were recorded

Calibration and precision of serum creatinine and plasma cystatin C measurement: impact on the estimation of glomerular filtration rate

Serum creatinine (SCr) is the main variable for estimating glomerular filtration rate (GFR). Due to interassay differences, the prevalence of chronic kidney disease (CKD) varies according to the assay used, and calibration standardization is necessary. For SCr, isotope dilution mass spectrometry (IDMS) is the gold standard. Systematic differences are observed between Jaffe and enzymatic methods. Manufacturers subtract 0.30 mg/dl from Jaffe results to match enzymatic results (‘compensated Jaffe method’). The analytical performance of enzymatic methods is superior to that of Jaffe methods. In the original Modification of Diet in Renal Disease (MDRD) equation, SCr was measured by a Jaffe Beckman assay, which was later recalibrated. A limitation of this equation was an underestimation of GFR in the high range. The Chronic Kidney Disease Epidemiology (CKD-EPI) consortium proposed an equation using calibrated and IDMS traceable SCr. The gain in performance was due to improving the bias whereas the precision was comparable. The CKD-EPI equation performs better at high GFR levels (GFR[60 ml/ min/1.73 m2). Analytical limitations have led to the recommendation to give a grade ([60 ml/min/1.73 m2) rather than an absolute value with the MDRD equation. By using both enzymatic and calibrated methods, this cutoff-grade could be increased to 90 ml/min/1.73 m2 (with MDRD) and 120 ml/min/1.73 m2 (with CKD-EPI). The superiority of the CKD-EPI equation over MDRD is analytical, but the precision gain is limited. IDMS traceable enzymatic methods have been used in the development of the Lund– Malmo¨ (in CKD populations) and Berlin Initiative Study equations (in the elderly). The analytical errors for cystatin C are grossly comparable to issues found with SCr. Standardization is available since 2011. A reference method for cystatin C is still lacking. Equations based on standardized cystatin C or cystatin C and creatinine have been proposed. The better performance of these equations (especially the combined CKD-EPI equation) has been demonstrated