Run-Around Membrane Energy Exchanger Prototype 4 Design and Laboratory Testing

The run-around membrane energy exchanger (RAMEE) is a novel design that utilizes a membrane and a liquid desiccant to transfer heat and moisture between remotely located ducts. A laminate membrane called AY Tech ePTFE (expanded polyetrafluoroethylene) was sourced based on the vapour diffusion resistance (VDR), liquid penetration pressure (LPP), modulus of elasticity (E), and price. The measured VDR, LPP and modulus for the AY Tech. membrane were 97±11 s/m, >82 kPa, and 387±32 MPa respectively. A laboratory model of RAMEE prototype 4 was constructed using the AY Tech. membrane. The effectiveness of the laboratory model was evaluated using the energy exchanger test facility. Airstream temperatures and relative humidity’s were measured at various location to determine the exchanger effectiveness. The highest total effectiveness values measured for prototype 4, at AHRI test conditions, were 52±16% and 47±7% for a net transfer unit (NTU) of 12.3 and a NTU of 5.0 respectively

The Intermediate Filament Network in Cultured Human Keratinocytes Is Remarkably Extensible and Resilient

The prevailing model of the mechanical function of intermediate filaments in cells assumes that these 10 nm diameter filaments make up networks that behave as entropic gels, with individual intermediate filaments never experiencing direct loading in tension. However, recent work has shown that single intermediate filaments and bundles are remarkably extensible and elastic in vitro, and therefore well-suited to bearing tensional loads. Here we tested the hypothesis that the intermediate filament network in keratinocytes is extensible and elastic as predicted by the available in vitro data. To do this, we monitored the morphology of fluorescently-tagged intermediate filament networks in cultured human keratinocytes as they were subjected to uniaxial cell strains as high as 133%. We found that keratinocytes not only survived these high strains, but their intermediate filament networks sustained only minor damage at cell strains as high as 100%. Electron microscopy of stretched cells suggests that intermediate filaments are straightened at high cell strains, and therefore likely to be loaded in tension. Furthermore, the buckling behavior of intermediate filament bundles in cells after stretching is consistent with the emerging view that intermediate filaments are far less stiff than the two other major cytoskeletal components F-actin and microtubules. These insights into the mechanical behavior of keratinocytes and the cytokeratin network provide important baseline information for current attempts to understand the biophysical basis of genetic diseases caused by mutations in intermediate filament genes

Assay precision and risk of misclassification at rule-out cut-offs for high-sensitivity cardiac troponin

Clinical trials and guidelines support the use of very low high-sensitivity cardiac troponin (hs-cTn) results to rule-out a myocardial infarction (MI) ( 1) ). The International Federation of Clinical Chemistry and Laboratory Medicine Committee on Clinical Applications of Cardiac Biomarkers committee, through a modeling approach, suggests assays need to have a lower limit near 3 ng/L and an analytical variation of 10% below 7 ng/L if these low values are to perform consistently in practice ( 2) ). Our objectives for the present study were to assess: i) if any type of instrument or individual instrument could achieve a coefficient of variation (CV) of ≤10% at very low hs-cTn cut-offs (i.e., targets) recommended in clinical pathways; ii) the frequency of results at the hs-cTn target, above the target and below the target, with the latter group representing potential misclassification to the low risk group where the target level would in the intermediate risk range.<br/

Fluorescent images of the K5/K14, F-actin and microtubule networks in NEB-1 K14wt-GFP and NEB-1 K14R125P-GFP keratinocytes fixed at 0% or 133% strain.

<p>Cells were treated with 1 µg/mL nocodazole (Nc) to disturb the F-actin network, or were untreated (control). The F-actin network was visualized with rhodamine-phalloidin (100 nM), and α-tubulin with immunofluorescence. K14-GFP proteins were expressed and visualized by fluorescence microscopy. Scale bar = 20 µm.</p

The green vital inclusion dye FDA and blue vital exclusion dye DAPI were used to test for necrosis after extreme strain in NEB-1 K14wt-GFP and NEB-1 K14R125P-GFP cells.

<p>The keratinocytes were stretched to a specific strain and then returned to the relaxed state for viability staining. Necrosis increased significantly with increasing cell strain (* = p<0.05; ** = p<0.001). No significant difference in viability was found between the NEB-1 K14wt-GFP and NEB-1 K14R125P-GFP keratinocytes after undergoing extreme uniaxial strain of 133% (p>0.1). Error bars are standard error. Scale bar = 20 µm.</p

Effect of osmotic shock on the keratin cytoskeleton in the two cell lines studied.

<p>A. NEB-1 K14wt-GFP (upper panel) and NEB-1 K14R125P-GFP (lower panel). Both cell lines were subjected to hypo-osmotic shock. Clear peripheral aggregates were seen in R125P cells 20 and 30 min after osmotic shock. No filament fragmentation or aggregates were observed for NEB-1 K14wt-GFP cells. Scale bar = 15 µm. B. Insets from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031320#pone-0031320-g003" target="_blank">Figure 3A</a>, 20 min after osmotic shock, showing K14 aggregates in the NEB-1 K14R125P-GFP cells, and reconstituted K14 filaments in the NEB-1 K14wt-GFP cells.</p

Fluorescent images of (A) NEB-1 K14wt-GFP and (B) NEB-1 K14R125P-GFP keratinocytes undergoing incremental uniaxial strain.

<p>The average cell strain is depicted in the top left corner of each image. The cytokeratin networks of the NEB-1 K14R125P-GFP cells withstood extreme cellular strains of 133% and there was no evidence of intermediate filament bundle rupture or the development of keratin aggregates (n = 10). Scale bar = 20 µm.</p