To the Editor: From our limited experience with the critical hypoxic COVID-19 patient under investigation who requires invasive ventilation, we have recreated a device from Dr Scott Weingart’s ...methodology1 for preoxygenation prior to intubation and for ventilatory support if deemed necessary. We have called it the closed PEEP (positive end-expiratory pressure) system (CPS)
Organic micropollutants such as estrogens occur in water in increasing quantities from predominantly anthropogenic sources. In water such micropollutants partition not only to surfaces such as ...membrane polymers but also to any other natural or treatment related surfaces. Such interactions are often observed as sorption in treatment processes and this phenomenon is exploited in activated carbon filtration, for example. Sorption is important for polymeric materials and this is used for the concentration of such micropollutants for analytical purposes in solid phase extraction. In membrane filtration the mechanism of micropollutant sorption is a relatively new discovery that was facilitated through new analytical techniques. This sorption plays an important role in micropollutant retention by membranes although mechanisms of interaction are to date not understood. This review is focused on sorption of estrogens on polymeric surfaces, specifically membrane polymers. Such sorption has been observed to a large extent with values of up to 1.2
ng/cm
2 measured. Sorption is dependent on the type of polymer, micropollutant characteristics, solution chemistry, membrane operating conditions as well as membrane morphology. Likely contributors to sorption are the surface roughness as well as the microporosity of such polymers. While retention—and/or reflection coefficient as well as solute to effective pore size ratio—controls the access of such micropollutants to the inner surface, pore size, porosity and thickness as well as morphology or shape of inner voids determines the available area for sorption. The interaction mechanisms are governed, most likely, by hydrophobic as well as solvation effects and interplay of molecular and supramolecular interactions such as hydrogen bonding, π-cation/anion interactions, π–π stacking, ion–dipole and dipole–dipole interactions, the extent of which is naturally dependent on micropollutant and polymer characteristics. Systematic investigations are required to identify and quantify both relative contributions and strength of such interactions and develop suitable surface characterisation tools. This is a difficult endeavour given the complexity of systems, the possibility of several interactions taking place simultaneously and the generally weaker forces involved.
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► Sorption plays an important role in micropollutant retention by membranes. ► Measured sorption was up to 1.2
ng/cm
2 for estrogens. ► The internally accessible surface area of polymers is important. ► Material differences are attributed to a combination of hydrophobic and supramolecular interactions. ► Methodologies need to be developed to measure such interactions qualitatively and quantitatively.
•Increased flow rate (30–70 L/h) reduces the boundary layer thickness (95–55 µm).•Selectivity of ED approaches one as the potential increases from 5 to 25 V.•Salinity reduces As(V) and F removal, ...whereas it does not affect NO3 removal.•As(V) removal is pH-dependent, while NO3 and F removal is pH-independent.
Nitrate, arsenic and fluoride are some of the most hazardous elements contaminating groundwater resources. In this work, the impact of operative (flowrate, electricpotential) and water quality (salinity, contaminant feed concentration, pH) parameters on brackish water decontamination was investigated using a batch electrodialysis (ED) system. Electrodialysis at low electric potentials (5 V) was more selective toward monovalent ions, at higher potentials (>15 V) removal of all ions increased and selectivity approached one, meaning removal of all ions. Changing the flowrate from 30 to 70 L/h, increased nitrate and fluoride removal slightly, while arsenic(V) removal was maximum at 50 L/h. Rising salinity delayed removal of ions with low ionic mobility and diffusivity (i.e. fluoride, arsenic(V)). Increased feed concentration of contaminants had no impact on removal values. pH variations did not impact the nitrate, fluoride and salinity removal, yet arsenic(V) removal was greatly pH dependent. This was explained in part by lower diffusivity and higher hydration number of bi- and trivalent species of arsenic(V) at basic pH. The results of this work showed the significance of ionic characteristics (diffusivity, ionic mobility, hydration number) in ED. Nitrate concentrations satisfied guideline threshold in all experiments with concentrations below 50 mg/L. Lowest arsenic(V) concentration was 35 µg/L at the highest electric potential, 25 V. Using ionic characteristics makes separation of different ions possible, providing new opportunities for ED in environmentally friendly processes (e.g. resource recovery and zero liquid discharge).
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This study examined the feasibility of nanofiltration (NF) and reverse osmosis (RO) in treating challenging natural tropical waters containing high fluoride and natural organic matter (NOM). A total ...of 166 water samples were collected from 120 sources within northern Tanzania over a period of 16months. Chemical analysis showed that 81% of the samples have fluoride levels exceeding the WHO drinking guideline of 1.5mg/L. The highest fluoride levels were detected in waters characterized by high ionic strength, high inorganic carbon and on some occasions high total organic carbon (TOC) concentrations.
Bench-scale experiments with 22 representative waters (selected based on fluoride concentration, salinity, origin and in some instances organic matter) and 6 NF/RO membranes revealed that ionic strength and recovery affected fluoride retention and permeate flux. This is predominantly due to osmotic pressure and hence the variation of diffusion/convection contributes to fluoride transport. Different membranes had distinct fluoride removal capacities, showing different raw water concentration treatability limits regarding the WHO guideline compliance. BW30, BW30-LE and NF90 membranes had a feed concentration limit of 30–40mg/L at 50% recovery.
NOM retention was independent of water matrices but is governed predominantly by size exclusion. NOM was observed to have a positive impact on fluoride removal. Several mechanisms could contribute but further studies are required before a conclusion could be drawn.
In summary, NF/RO membranes were proved to remove both fluoride and NOM reliably even from the most challenging Tanzanian waters, increasing the available drinking water sources.
•Natural water sources sampled from northern Tanzania indicated high fluoride, inorganic carbon and NOM content.•Effects of operating conditions and water compositions on F and NOM removal by NF/RO were examined for many natural waters.•A positive effect of NOM on F retention is reported for these natural waters.
Micropollutants in the aquatic environment pose a high risk to both environmental and human health. The photocatalytic degradation of steroid hormones in a flow-through photocatalytic membrane ...reactor under UV light (365 nm) at environmentally relevant concentrations (50 ng l–1 to 1 mg l–1) was examined using a polyethersulfone–titanium dioxide (PES–TiO2) membrane. The TiO2 nanoparticles (10–30 nm) were immobilized both on the surface and in the nanopores (220 nm) of the membrane. Water quality and operational parameters were evaluated to elucidate the limiting factors in the degradation of steroid hormones. Flow through the photocatalytic membrane increased contact between the micropollutants and ·OH in the pores. Notably, 80% of both oestradiol and oestrone was removed from a 200 ng l–1 feed (at 25 mW cm–2 and 300 l m–2 h–1). Progesterone and testosterone removal was lower at 44% and 33%, respectively. Increasing the oestradiol concentration to 1 mg l–1 resulted in 20% removal, whereas with a 100 ng l–1 solution, a maximum removal of 94% was achieved at 44 mW cm–2 and 60 l m–2 h–1. The effectiveness of the relatively well-known PES–TiO2 membrane for micropollutant removal has been demonstrated; this effectiveness is due to the nanoscale size of the membrane, which provides a high surface area and facilitates close contact of the radicals with the very small (0.8 nm) micropollutant at an extremely low, environmentally relevant concentration (100 ng l–1).A polyethersulfone–titanium dioxide membrane is demonstrated to be effective at micropollutant removal during the photocatalytic degradation of steroid hormones in a flow-through photocatalytic membrane reactor under UV light at environmentally relevant concentrations.
Introduction
The objective of this study was to evaluate the cortical thickness and the volume of deep gray matter structures, measured from 3D T1-weighted gradient echo imaging, and white matter ...integrity, by diffusion tensor imaging (DTI) in patients with typical absence epilepsy (AE).
Methods
Patients (
n
= 19) with typical childhood AE and juvenile AE, currently taking antiepileptic medication, were compared with control subjects (
n
= 19), matched for gender and age. 3D T1 magnetization-prepared rapid gradient echo-weighted imaging and DTI along 30 noncolinear directions were performed using a 1.5-T MR scanner. FreeSurfer was used to perform cortical volumetric reconstruction and segmentation of deep gray matter structures. For tract-based spatial statistics analysis of DTI, a white matter skeleton was created, along with a permutation-based inference with 5000 permutations. A threshold of
p
< 0.05 was used to identify abnormalities in fractional anisotropy (FA). The mean, radial, and axial diffusivities were also projected onto the mean FA skeleton.
Results
Patients with AE presented decreased FA and increased mean diffusivity and radial diffusivity values in the genu and the body of the corpus callosum and right anterior corona radiata, as well as decreased axial diffusivity in the left posterior thalamic radiation, inferior cerebellar peduncle, right cerebral peduncle, and right corticospinal tract. However, there were no significant differences in cortical thickness or deep gray matter structure volumes between patients with AE and controls.
Conclusion
Abnormalities found in white matter integrity may help to better understand the pathophysiology of AE and optimize diagnosis and treatment strategies.
ERM proteins at a glance McClatchey, Andrea I
Journal of cell science,
08/2014, Letnik:
127, Številka:
Pt 15
Journal Article
Recenzirano
Odprti dostop
The cell cortex is a dynamic and heterogeneous structure that governs cell identity and behavior. The ERM proteins (ezrin, radixin and moesin) are major architects of the cell cortex, and they link ...plasma membrane phospholipids and proteins to the underlying cortical actin cytoskeleton. Recent studies in several model systems have uncovered surprisingly dynamic and complex molecular activities of the ERM proteins and have provided new mechanistic insight into how they build and maintain cortical domains. Among many well-established and essential functions of ERM proteins, this Cell Science at a Glance article and accompanying poster will focus on the role of ERMs in organizing the cell cortex during cell division and apical morphogenesis. These examples highlight an emerging appreciation that the ERM proteins both locally alter the mechanical properties of the cell cortex, and control the spatial distribution and activity of key membrane complexes, establishing the ERM proteins as a nexus for the physical and functional organization of the cell cortex and making it clear that they are much more than scaffolds. This article is part of a Minifocus on Establishing polarity.
Comparison of nanofiltration characterization data from literature is challenging due to different hydrodynamics and system designs, which affect membrane retention. In this study, stirred cell (SC), ...micro and macro cross flow systems (micro and macro CF) with different configuration were used to measure salt and organic tracer retention. Minimal concentration polarization conditions were applied in order to:1)evaluate comparability of the systems for characterization of membrane pore radius and molecular-weight-cut-off,2)understand the impact of system configuration and operation on mass transfer,3)compare salt retention at laboratory scale with the retention of spiral wound module.
Results indicated that system dimension was the most important parameter to affect the mass transfer and the concentration of both salt and organic tracers on the membrane surface (Cm) in the macro CF system. Indeed, the higher channel length to width ratio of macro CF was related to reduced mass transfer and higher Cm. However, a comparability of the three systems was observed by operating at low flux (below 80 L/m2h) and higher cross flow velocity (above 0.4 m/s), where the lowest concentration polarization conditions were maintained. This is valid taking into account the variation of hydrodynamics (e.g. relation of Sherwood number and Reynolds range), which is intrinsically related to the different operation modes of dead end and cross flow. This study gives a novel contribution to improve the accuracy of membrane characterization methodologies and to identify suitable operative conditions for testing new membrane materials at small scale.
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•Salt retention in micro CF is similar to SWM at minimal concentration polarization condition.•Larger scale (length) dimension in macro CF reduces mass transfer and retention.•Loose NF membrane retention is affected more by system design than tight membrane.•MWCO and pore radius estimated with organic tracer are comparable in all three systems.
The objective of this study was to evaluate the impact of pH on boron, fluoride, and nitrate retention by comparing modelled speciation predictions with retention using six different nanofiltration ...(NF) and reverse osmosis (RO) membranes (BW30, ESPA4, NF90, TFC-S, UTC-60, and UTC-80A). Retention was explained with regard to speciation, membrane properties, and ion properties such as charge, hydrated size, and Gibbs energy of hydration. Flux was independent of pH, indicating that pH did not alter pore size and hence permeability for all membranes except UTC-60. Membrane charge (zeta potential) was strongly dependent on pH, as expected. Boron and fluoride retention depended on membrane type, pH, which correlated closely to contaminant speciation, and was due both to size and charge exclusion. While retention at low and neutral pH was a challenge for boron, high boron retention was achieved (>
70% above pH 11). Fluoride retention was generally >
70% above pH 7. Nitrate retention depended on membrane, and was mostly pH independent (as was the speciation). The presence of a background electrolyte matrix (20
mM NaCl and 1
mM NaHCO
3) reduced nitrate and boron retention (at high pH) due to charge shielding, and enhanced the retention of fluoride in single feed solutions, suggesting preferential transport of Cl
− compared to F
− with Na
+.
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