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A constant-number direct simulation Monte Carlo (DSMC) model was developed for the analysis of nanoparticle (NP) agglomeration in aqueous suspensions. The modeling approach, based on the "particles in a box" simulation method, considered both particle agglomeration and gravitational settling. Particle-particle agglomeration probability was determined based on the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and considerations of the collision frequency as impacted by Brownian motion. Model predictions were in reasonable agreement with respect to the particle size distribution and average agglomerate size when compared with dynamic light scattering (DLS) measurements for aqueous TiO(2), CeO(2), and C(60) nanoparticle suspensions over a wide range of pH (3-10) and ionic strength (0.01-156 mM). Simulations also demonstrated, in quantitative agreement with DLS measurements, that nanoparticle agglomerate size increased both with ionic strength and as the solution pH approached the isoelectric point (IEP). The present work suggests that the DSMC modeling approach, along with future use of an extended DLVO theory, has the potential for becoming a practical environmental analysis tool for predicting the agglomeration behavior of aqueous nanoparticle suspensions.

Double-Pulsed-Field-Gradient (d-PFG) MR is emerging as a powerful new means for obtaining unique microstructural information in opaque porous systems that cannot be obtained by conventional single-PFG (s-PFG) methods. The angular d-PFG MR methodology is particularly important since it can utilize the effects of microscopic anisotropy (μA) and compartment shape anisotropy (csA) in the E(ψ) profile at the different t(m) regimes to provide detailed information on compartment size and eccentricity. An underlying assumption is that the PFGs that are imparted to weigh diffusion are the only gradients present; however, in realistic systems and especially where there are randomly oriented anisotropic pores, susceptibility effects may induce strong internal gradients. In this study, the effects of such internal gradients on E(ψ) plots obtained from angular d-PFG MR and on microstructural information that can be obtained from s-PFG and d-PFG MR were investigated. First, it was found that internal gradients induce a bias in the s-PFG MR results, thus creating an anisotropy that is not related to microstructure, termed apparent-Susceptibility-Induced-Anisotropy (aSIA). We then show that aSIA effects are also manifest in different ways in the angular d-PFG MR experiment in controlled phantoms and in realistic systems such as quartz sand, emulsions, and biological systems. The effects of aSIA in some cases completely masked the effects of μA and csA; however, we subsequently show that by introducing bipolar gradients to the d-PFG MR (bp-d-PFG), the effects of aSIA can be largely suppressed, restoring the E(ψ) plots that are expected from the theory along with the microstructural information that it conveys. We conclude that when specimens are characterized by strong internal gradients, the novel information on μA and csA that is manifest in the E(ψ) plots can indeed be inferred when bp-d-PFG MR is used, i.e. when bipolar gradients are applied.

Summary The phosphoinositide 3-kinase (PI3K)/v-akt murine thymoma (AKT) viral oncogene pathway is involved in regulating the signaling of multiple biological processes such as apoptosis, metabolism, cell proliferation, and cell growth. Mutations in the genes associated with the PI3K/AKT pathway including PI3K , AKT , RAS and PTEN , are infrequently found within head and neck squamous cell carcinoma and more specifically are rarely reported in oral squamous cell carcinoma (OSCC) cases. We aimed to investigate the frequency of mutations in AKT1 , PTEN , PIK3CA , and RAS ( K-RAS , N-RAS , H-RAS ) genes in 37 cases of oral squamous cell carcinoma (OSCC). Mutational analysis of PTEN , RAS , PIK3CA and AKT genes was performed using chip-based matrix-assisted laser desorption time-of-flight (MALDI-TOF) mass spectrometry and by direct sequencing. The only gene mutated in our series was the PIK3CA . Missense mutations of the PIK3CA gene were found in 4 of our cases (10.8%); no correlation has been found with oral location, stage and survival. The absence of mutations in AKT1 , PTEN , and RAS genes in the present study is in accordance with previous studies confirming that these genes are rarely mutated in OSCC. Our data confirm that PIK3CA is important to OSCC tumorigenesis and can contribute to oncogene activation of the PIK3CA / AKT pathway in OSCC. The knowledge of the PIK3CA’s involvement in OSCC is important because a specific kinase inhibitor could be considered as a future therapeutic option for OSCC patients with PIK3CA mutations.

The mineral scaling propensity of aromatic polyamide membrane surfaces was evaluated for surfaces ranging in roughness from about 1 to 94 nm, surface feature heights ranging from a few nanometers to as high as 400–450 nm and average peak separation of ∼140 nm to 2 μm. The polyamide surfaces were interfacially polymerized onto quartz crystal microbalance (QCM) sensors and silicon wafer substrates which were previously structured with a polyelectrolyte film formed by a layer-by-layer self-assembly method. Mineral scaling was quantified via QCM measurements of the time evolution of surface crystallization along with SEM and AFM surface characterization. Crystal surface mass density and rate of surface crystallization increased with increasing surface roughness. However, surface scaling propensity was also significantly impacted by the details of surface topography revealing fewer but larger crystals on rough surfaces that possessed large features with large separation distances. It is hypothesized that the separation distance between features and feature heights (dictating the geometry of surface “valleys”), for a given surface roughness, could affect the availability of surface nucleation sites as well as constrain growth of crystals within surface valleys.

Accurately characterizing pore morphology is of great interest in a wide range of scientific disciplines. Conventional single-Pulsed-Field-Gradient (s-PFG) diffusion MR can yield compartmental size and shape only when compartments are coherently ordered using the q-space approaches that necessitate strong gradients. However, the double-PFG (d-PFG) methodology can provide novel microstructural information even when specimens are characterized by polydispersity in size and in shape, and even when anisotropic compartments are randomly oriented. In this study, for the first time, we show that angular d-PFG experiments can be used to accurately measure cellular size and shape anisotropy of fixed yeast cells using relatively weak gradients. The cell size, as measured by light microscopy was found to be 5.32±0.83 μm, while the results from the non-invasive angular d-PFG experiments yielded a cell size of 5.46±0.45 μm. Moreover, the low shape anisotropy of the cells could be inferred from experiments conducted at long mixing times. Finally, similar experiments were conducted in a phantom comprised of anisotropic compartments that were randomly oriented, showing that angular d-PFG MR provides novel information on compartment eccentricity that could not be accessed using conventional methods. The angular d-PFG methodology seems promising for accurate estimation of compartment size and compartment shape anisotropy in heterogeneous systems in general and biological cells and tissues in particular.

An approach to real-time analysis of mineral scale formation on reverse osmosis (RO) membranes was developed using an ex-situ direct observation membrane monitor (MeMo). The purpose of such monitoring is to signal the onset of mineral scaling and provide quantitative information in order to appropriately initiate system cleaning/scale dissolution. The above is enabled by setting the MeMo operating conditions (cross flow velocity and transmembrane pressure) to closely match the conditions in the monitored membrane plant (e.g., in the tail RO element) in order to mimic the surface scaling processes taking place inside the monitored RO plant element. Mineral scale in the MeMo system is monitored by comparison of consecutive images of the membrane surface for the purpose of determining the evolution of the fractional coverage by mineral salt crystals and the corresponding crystal count in the monitored region. Through online image analysis, once crystal growth is determined to be above a prescribed threshold, one can then initiate any number of cleaning protocols. Through early detection of membrane scaling (i.e., before permeate flux decline is observed), enabled by the present monitoring approach, the system operator can prevent irreversible membrane damage and loss of system productivity.

This study evaluated intermediate chemical demineralization (ICD) as a technique for overcoming mineral salt solubility limits that constrain the water recovery of reverse osmosis (RO) desalting. An empirical approach was developed to determine theoretical cation removal set points for ICD based on predetermined process design and operation guidelines to facilitate increasing the overall water recovery of Colorado River water desalting from 85% (i.e., in the primary RO unit) to 95% via a secondary RO (SRO) unit. Additionally, the study evaluated whether microfiltration (MF) or dual-media filtration (DMF) could serve as the filtration step prior to the secondary reverse osmosis (SRO) unit. The model suggested ranges for ICD influent total-carbonate-to-calcium ratios and ICD effluent pH to simultaneously mitigate barium sulfate, calcium sulfate, and silica scaling. MF was preferred over DMF as the filtration step prior to SRO based on significantly lower filter effluent turbidity and silt density indices. The overall PRO-ICD-SRO system operated for over 550 h at 95% total RO water recovery without evidence of scaling of the terminal RO elements, validating the cation removal set points developed through the ICD model and demonstrating the utility of ICD.

Surface crystallization of calcium sulfate dihydrate (gypsum) on a series of polymeric surfaces was studied using a quartz microbalance system. Polyelectrolyte multilayer films (positively and negatively charged surfaces) were formed on the quartz crystal microbalance (QCM) sensors utilizing a layer-by-layer spin-assembly method. The kinetics of gypsum surface crystallization was quantified in terms of the evolution of gypsum mineral scale on the different surfaces. For comparison mineral scaling was also evaluated on silica and polyamide surfaces. For surfaces of the same charge polarity (+/-), the mass density of gypsum scale was lower (PSS < PAA, PEI < PAH) for smoother surfaces. The extent of surface mineral scaling (quantified in terms of both mass density and aerial coverage) were the combined result of the rate of nucleation and crystal growth kinetics. Although aerial scale coverage correlated with the crystal mass density, the crystal number density did not correlate with the extent of surface scaling. Surface crystal size, morphology and crystal number density varied significantly at similar roughness levels, suggesting that surface chemical functionality may also affect surface crystallization. The present results suggest that there is merit in exploring methods for mitigation of mineral scaling on polymeric surfaces via alteration of surface both surface topography and chemistry. In this regards, an expanded systematic study is needed in order to quantitatively clarify the interplay between the above two factors in controlling surface crystallization.

Most in vitro toxicity studies on engineered nanomaterials (ENMs) use transformed rather than primary cells for logistical reasons. However, primary cells may provide a more appropriate connection to in vivo toxicity because these cells maintain their phenotypic fidelity and are also capable of differentiating into lineages that may be differently affected by potentially hazardous ENM. Few studies to date have focused on the role of cellular differentiation in determining ENM toxicity. We compared the response of undifferentiated and differentiated primary human bronchial epithelial cells (NHBE) to cationic mesoporous silica nanoparticles (MSNP) that are coated with polyethyleneimine (PEI) since this polymer is known to exert differential cytotoxicity depending on its molecular weight and cationic density. The attachment of cationic PEI polymers to the MSNP surface was used to assess these materials' toxicological potential in undifferentiated and differentiated human bronchial epithelial cells (NHBE), using of a multi-parametric assay that screens for an integrated set of sub-lethal and lethal response outcomes. MSNP coated with high molecular weight (10 and 25 kD) polymers were more toxic in differentiated cells than particles coated with shorter length polymers. The increased susceptibility of the differentiated cells is in agreement with more abundant expression of a proteoglycan, syndecan-1, which contains copious heparin sulfate side chains. Pre-treatment with heparinase to remove the negatively charged sulfates decreased MSNP-PEI binding to the cell surface and lowered the cytotoxic potential of the cationic particles. These data demonstrate the importance of studying cellular differentiation as an important variable in the response of primary cells to toxic ENM properties.

Diffusion MR has become one of the most important tools for studying neuronal tissues. Conventional single-pulsed-fieldgradient methodologies are capable of faithfully depicting diffusion anisotropy in coherently ordered structures, providing important microstructural information; however, it is extremely difficult to characterize randomly oriented compartments using conventional single-pulsed-field-gradient MR. The angular double-pulsed-field-gradient methodology can potentially overcome the limitations of conventional single-pulsed-field-gradient MR, and offer microstructural information on microscopic anisotropy and compartment shape anisotropy even when anisotropic compartments are completely randomly oriented. Here, we used angular double-pulsed-field-gradient MR at different mixing times to study isolated gray matter and white matter, respectively, and the results are compared with phantoms in which compartments are randomly oriented and coherently organized, respectively. We find that angular bipolar double-pulsed-fieldgradient MR offers novel microstructural information, especially in the gray matter, depicting the local microscopic and compartment shape anisotropies present. Furthermore, direct comparison between the angular dependencies arising from white and gray matter at different mixing times reveals signatures for these tissues that are based on compartment shape anisotropy. These findings demonstrate that microstructural information can indeed be obtained from gray matter, and therefore, angular double-pulsed-field-gradient MR is promising for future application in MRI of the central-nervous-system. Magn Reson Med 65:1216–1227, 2011. V C 2011 Wiley-Liss, Inc.

The response of a murine macrophage cell line exposed to a library of seven metal and metal oxide nanoparticles was evaluated via High Throughput Screening (HTS) assay employing luciferase-reporters for ten independent toxicity-related signaling pathways. Similarities of toxicity response among the nanoparticles were identified via Self-Organizing Map (SOM) analysis. This analysis, applied to the HTS data, quantified the significance of the signaling pathway responses (SPRs) of the cell population exposed to nanomaterials relative to a population of untreated cells, using the Strictly Standardized Mean Difference (SSMD). Given the high dimensionality of the data and relatively small dataset the validity of the SOM clusters was established via a consensus clustering technique. Analysis of the SPR signatures revealed two cluster groups corresponding to (i) sub-lethal pro-inflammatory responses to Al2O3, Au, Ag, SiO2 nanoparticles possibly related to ROS generation, and (ii) lethal genotoxic responses due to exposure to ZnO and Pt nanoparticles at a concentration range of 25 μg/mL-100 μg/mL at 12 h exposure. In addition to identifying and visualizing clusters and quantifying similarity measures, the SOM approach can aid in developing predictive quantitative-structure relations; however, this would require significantly larger datasets generated from combinatorial libraries of engineered nanoparticles.

Basic research in the chemistry of hexameric resorcin[4]arenes and pyrogallol[4]arenes during the last decade is reviewed. Applications of NMR methods to determine solution structures, host guest properties and exchange dynamics are discussed. The scientific issue is the behavior of molecules in small spaces; the challenge is to translate this information to practical applications in, say, catalysis or transport.

Double pulsed-field gradient (d-PFG) MRI can provide quantitative maps of microstructural quantities and features within porous media and tissues. We propose and describe a novel MRI phantom, consisting of wafers of highly ordered glass capillary arrays (GCA), and its use to validate and calibrate a d-PFG MRI method to measure and map the local pore diameter. Specifically, we employ d-PFG Spin-Echo Filtered MRI in conjunction with a recently introduced theoretical framework, to estimate a mean pore diameter in each voxel within the imaging volume. This simulation scheme accounts for all diffusion and imaging gradients within the diffusion weighted MRI (DWI) sequence, and admits the violation of the short gradient pulse approximation. These diameter maps agree well with pore sizes measured using both optical microscopy and single PFG diffusion diffraction NMR spectroscopy using the same phantom. Pixel-by-pixel analysis shows that the local pore diameter can be mapped precisely and accurately within a specimen using d-PFG MRI.

A two-step chemically-enhanced seeded precipitation (CESP) process was demonstrated for accelerated desupersaturation of antiscalant-containing, gypsum-supersaturated model solutions, which mimicked reverse osmosis (RO) concentrate from RO desalting of agricultural drainage water of high mineral scaling propensity. In the CESP process, CaCO3 precipitation is first induced via lime dosing for antiscalant scavenging, followed by subsequent CaSO4 precipitation via gypsum seeding for concentrate desupersaturation. It was demonstrated that lime-precipitated CaCO3 particles were able to scavenge generic and commercial polycarboxylic-acid antiscalants, thereby facilitating subsequent CaSO4 precipitation to progress with minimal retardation. The study demonstrated via a series of batch CESP cycles that gypsum particle recycling can sustain CaSO4 precipitation, suggesting that a continuous CESP process could be feasible. Process analysis suggests that CESP can be significantly less chemical-intensive than conventional precipitation softening and, with its integration as an intermediate RO concentrate demineralization process, can enable desalination water recovery enhancement via secondary RO desalting. For the present case of gypsum-saturated RO feed water, enhancement of overall water recovery from 63% up to 87% or higher appears to be feasible. The study suggests that there is merit for developing a continuous CESP process for high recovery RO desalting of brackish water of high gypsum scaling propensity.

This work focuses on the design and implementation of an optimization-based control system on an experimental reverse osmosis (RO) membrane water desalination process in order to facilitate system operation at an energy optimal condition. A dynamic nonlinear lumped-parameter model for the RO process is derived using first principles and the model parameters are computed from experimental data to minimize the error between model predictions and actual system response. This model, along with several equations for reverse osmosis system energy analysis, are combined to form the basis for the design of a nonlinear optimization-based control system. The proposed control system is implemented on UCLA's experimental RO system and its energy optimization capabilities are evaluated.

An experimental method was developed for quantifying mineral scale nucleation and growth on RO membranes enabling comparison of the effectiveness of antiscalants in retarding mineral scale formation. Mineral scale growth and inhibition was evaluated, for calcium sulfate dihydrate (gypsum) as a model scalant, from direct visual observations of crystal growth on the membrane surface in a plate-and-frame RO cell. Comparison of membrane scaling with and without the use of antiscalants was carried out based on RO scaling tests conducted under identical operating conditions with respect to the initial flux and crossflow velocity, at identical initial concentration fields within the RO membrane channel and at the membrane surface. The range of gypsum saturation index (SIg) at the membrane surface was 1.3–2.3 enabling determination of gypsum scaling for the above SIg range from a single RO scaling test, given direct observation of crystal nucleation and growth on the membrane surface. The present work demonstrates that it is possible to distinguish antiscalants modes of scale inhibition and corresponding scale suppression effectiveness, over a reasonable range of solution supersaturation. The current approach introduces antiscalant crystal nucleation and growth retardation factors that can aid in the development, selection and dose optimization of antiscalants for use in RO desalination.

Various mixing operations between the feed, retentate and permeate streams are studied in this work to determine their effectiveness in decreasing the specific energy consumption (SEC) of single-stage (single-pass), two-pass and two-stage reverse osmosis (RO) processes operated at the limit of the thermodynamic restriction. The results show that in a single-stage RO process, partial retentate recycling to the feed stream does not change the SEC, while partial permeate recycling to the feed stream increases the SEC if targeting the same overall water recovery. Energy optimization of two-pass membrane desalination, with second-pass retentate recycling to the first-pass feed stream and operated at the limit imposed by the thermodynamic restriction, revealed the existence of a critical water recovery. When desalting is accomplished at recoveries above the critical water recovery, two-pass desalination with recycling is always less efficient than single-pass desalination. When desalting is accomplished at recoveries below the critical water recovery, an operational sub-domain exists in which the SEC for a two-pass process with recycling can be lower than for a single-pass counterpart, when the latter is not operated at its globally optimal state. For the two-stage RO process, diverting part of the raw feed to the second stage, in order to dilute the feed to the second-stage RO, does not decrease the minimal achievable SEC of a two-stage RO process. The various mixing approaches, while may provide certain operational or system design advantages (e.g., with respect to achieving target salt rejection for certain solutes or flux balancing), do not provide an advantage from an energy usage perspective.

Hydrogen-bond molecular capsules of resorcin[4]arenes (1) and pyrogallol[4]arenes (2) attracted much interest in the last decade. It was found, for example, that resorcin[4]arenes form hexameric capsules in non-polar organic solvents that can accommodate both trialkylamines and tetraalkylammonium salts. In search for the bulkiest guest that can be accommodated in the cavity of such capsules we found, with the aid of diffusion NMR, that such guests can interact also with the external surface of the hexameric capsules. Interestingly, monitoring the effect of CD3OD titration on the diffusion coefficients of the different components in such host–guest systems indicates that the interaction of such guests with the external surface of the hexameric capsule is significant and can be found also in case where guest's encapsulation occurs as in the case of trioctylamine (3) and tetraoctylammonium bromide (6). These CD3OD titrations showed also that these interactions are disrupted before the hexamer is disrupted an...

Purpose: To assess, by MR spectroscopy (MRS) and diffusion weighted imaging (DWI), the ability of electrical stimulation of the sphenopalatine ganglion (SPG) to augment stroke recovery in transient middle cerebral artery occluded (t-MCAO) rats, when treatment is started 18 6 2 h post-occlusion. Materials and Methods: 1 H-MRS imaging ( 1 H-MRSI) and DWI were used to evaluate ischemic brain tissue after SPG stimulation in rats subjected to 2 h of t-MCAO. Rats were examined by 1 H-MRSI, DWI, and behavioral tests at 16 6 2 h, 8 days, and 28 days post-MCAO. Results: N-Acetyl-aspartate (NAA) levels of the stimulated and control rats were the same 16 6 2 h post-MCAO (0.52 6 0.03, 0.54 6 0.03). At 28 days post-occlusion, NAA levels were significantly higher in the treated group (0.60 6 0.04) compared with those of the untreated animals (0.50 6 0.04; P < 0.05). This effect was more pronounced for regions with low NAA values (0.16 6 0.03) that changed to 0.32 6 0.03 (P ¼ 0.04) for the treated group and to 0.10 6 0.03 (P ¼ 0.20) for the controls. DWI data showed better ischemic tissue condition for the treated rats, but the measured parameters showed only a trend of improvement. The MR results were corroborated by behavioral examinations. Conclusion: Our findings suggest that SPG stimulation may ameliorate MR tissue characteristics following t-MCAO even if treatment is started 18 h post-occlusion.

Surface nano-structuring of polyamide desalination membrane with a hydrophilic poly(methacrylic acid) was shown to reduce the membrane mineral scaling propensity as demonstrated with calcium sulfate dihydrate (gypsum). A two-step approach was employed, whereby the active polyamide (PA) layer of a thin-film composite (TFC) synthesized membrane was activated with impinging atmospheric plasma, followed by a solution free-radical graft polymerization (FRGP) of a water soluble methacrylic acid (MAA) monomer, at 60 °C and initial monomer concentration of 5–20% (v/v), onto the surface of the PA-TFC membrane. The approach of creating a layer of end-grafted poly(methacrylic acid) (PMAA) surface chains was first developed and evaluated using a surrogate polyamide membrane layer interfacially polymerized onto a thin poly(ethyleneimine) (PEI) film coated onto a silicon wafer. The resulting PMAA–PA-PEI–Si surrogate membrane surface was hydrophilic with a water contact angle range of 10–17°. Structuring of the PA-TFC membrane at equivalent FRGP reaction conditions resulted in membranes of higher permeability (by a factor of 1.3–2.26) relative to a commercial RO membrane of a similar surface roughness (∼70 nm) and salt rejection. Flux tests of membrane mineral scaling demonstrated that membrane mineral scaling propensity can be measurably reduced, relative to commercial membrane of the same salt rejection, while yielding equivalent or higher water permeability. The onset time for gypsum scaling for the optimal membrane surface (prepared at 10% (v/v) initial MAA concentration) was retarded by a factor of 2–5 relative to the commercial RO membrane. Current work is ongoing to further optimize the surface structure in order to increasing scaling resistance and assess the impact of surface structuring on nucleation of mineral salt crystals.

The technical viability of RO desalination technology was demonstrated in the late 1950's by the pioneering work of Sidney Loeb and Srinivasa Sourirajan and a team of researchers at the University of California, Los Angeles (UCLA) led by Professors Joseph McCutchan and Samuel Yuster. Today Reverse osmosis (RO) membrane desalination is a mature process for the production of potable water from seawater and inland brackish water. RO membranes are also now widely used as part of the overall process for the treatment of wastewater for reclamation and reuse for irrigation, industrial, and groundwater recharge applications. RO desalination technology is used worldwide and has made it possible to develop new potable water sources in areas of the world where freshwater water sources are scarce.

Reverse osmosis (RO) water desalination is now well established as a mature water desalination technology. With the current generation of seawater and brackish-water RO membranes, it is now both economically and technically feasible to desalt brackish water and seawater on a large scale. In order to further expand the applications of RO desalting technologies, optimal process conditions must be selected to minimize water production costs associated with energy consumption, membrane replacement costs, chemical usage, and residual brine concentrate management. In the present review, a multi-pronged process-optimization approach for reverse osmosis desalination is presented. A theoretical framework discussed for optimizing energy consumption with and without energy recovery devices (ERDs), considering the impact of membrane replacement and brine management costs. The approach enables quantification of the optimal water recovery of RO desalting, considering various factors including the use of energy recovery...

Quinolinic acid (QA) induced striatal lesion is an important model for excitotoxicity that is also used for efficacy studies. To date, the morphological and spectroscopic indices of this model have not been studied longitudinally by MRI; therefore the objectives of this study were aimed at following the lesion progression and changes in N-acetyl aspartate (NAA) as viewed by MRI and MRSI, respectively, in-vivo over a period of 49 days. We found that the affected areas exhibited both high and low apparent diffusion coefficients (ADC) even 49 days post QA injection in three of the six tested animals. MRI-guided histological analysis correlated areas characterized by high ADCs on day 49 with cellular loss, while areas characterized by lower ADCs were correlated with macrophage infiltration (CD68 positive stain). Our MRSI study revealed an initial reduction of NAA levels in the lesioned striatum, which significantly recovered with time, although not to control levels. Total-striatum normalized NAA levels recovered from 0.67 +/- 0.15 (of the contralateral row) on day 1 to 0.90 +/- 0.12 on day 49. Our findings suggest that NAA should be considered as a marker for neuronal dysfunction, in addition to neuronal viability. Some behavioral indices could be correlated to permanent neuronal damage while others demonstrated a spontaneous recovery parallel to the NAA recovery. Our findings may have implications in efficacy-oriented studies performed on the QA model.

An analysis of the impact of increasing RO membrane permeability on the reduction in water desalination cost was carried out for RO desalting operated up to the limit imposed by the thermodynamic restriction. The premise of the present assessment is that, the current generation of high permeability RO membranes makes it feasible to carry out RO desalination up to the thermodynamic restriction limit. In this limit, the ratio of membrane to energy cost can be expressed as a function of the water recovery level and a dimensionless cost parameter that accounts for the purchase cost of electrical energy and membrane area, as well as feed water salinity, salt rejection requirement and membrane permeability. The present analysis suggests that, given the present day electrical energy and membrane prices, the benefit of developing membranes of even greater permeability is primarily at low water recoveries for inland brackish water desalting. At low water recoveries, however, there is typically an added cost associated with brine management for inland water desalting. In RO desalting of seawater, on the other hand, the specific cost (i.e., per permeate produced) of energy is much higher relative to the membrane cost, and there is lower economic incentive for developing higher permeability membranes if the objective is to lower the cost of seawater desalination. The analysis suggests that further significant improvement in RO membrane permeability is less likely to be the primary driver for a major reduction in the cost of seawater desalination. However, it is expected that significant reduction in RO water production cost can arise from a variety of other process improvements including, but not limited to, development of improved fouling-resistant membranes, more effective and lower feed pretreatment and brine management costs, optimization of process configuration and control schemes, as well as utilization of low cost renewable energy sources.

The energy optimization of two-pass membrane desalination, at the limit imposed by the thermodynamic restriction, was investigated and compared with a single-pass membrane desalting operation at the equivalent targeted overall salt rejection and permeate product recovery. The analysis considered the effect of pump and energy recovery efficiencies, membrane rejection, and retentate recycling from the second to the first-pass. The optimization results suggest that when the desired overall salt rejection can be achieved via a single-pass, then this process configuration will result in a lower specific energy consumption (SEC) relative to the two-pass membrane desalting process. However, if the desired overall rejection (or specific ion rejection, e.g., boron) cannot be achieved with the highest available rejection membrane in a single-pass, then a two-pass configuration is a feasible solution. In the latter case, the lowest energy consumption will be attained when a membrane of the highest available salt rejection is used in the first-pass. In cases in which desalting is accomplished at recoveries below the critical water recovery (i.e., the optimal recovery for a single stage), an operational sub-domain may exist in which the SEC for a two-pass process can be lower than for a single-pass counterpart, but only if the single-pass process is not operated at its globally optimal state. Retentate recycling from the second-pass to the first-pass feed can reduce the SEC for the two-pass process. However, optimization solution of the two-pass process is always a single-pass process as the optimal desalination process.

A 3-D (3-dimensional) numerical modeling approach to analyze the coupling of mineral scale, concentration polarization and permeate flux was developed and demonstrated for a gypsum membrane scaling test in a plate-and-frame RO membrane module geometry. The impact of concentration polarization on mineral gypsum scaling, and in turn the impact of mineral scale on the concentration polarization field, were explored via 3-D finite-element numerical solutions of the coupled fluid hydrodynamics and solute mass transfer equations, along with detailed experimental data on the extent and location of mineral scale. Numerical simulations of the concentration field for a scale-free membrane revealed that the regions of highest supersaturation with respect to calcium sulfate corresponded to regions of highest gypsum scale density, as observed through real-time imaging of the membrane surface in the gypsum scaling test. 3-D simulations of the concentration field in the presence of mineral scale revealed that the concentration polarization modulus and permeate flux were largely unaffected in contiguous scale-free regions of the membrane. However, near and just downstream of individual crystal formations, the local concentration polarization modulus decreased (by ∼5%) and the permeate flux increased (by ∼2%) relative to the same positions in the absence of scale. The model-calculated and experimental permeate flux decline agreed closely with an average absolute error of 1.8%. The present study suggests that flux decline due to mineral scaling can be reasonably described by the surface blockage mechanism.

The feasibility of operating brackish water reverse osmosis (BWRO) desalination in a feed flow reversal (FFR) mode so as to mitigate mineral scaling was evaluated with feed solutions containing calcium, sodium, sulfate and chloride ions. The premise of the FFR approach is to enable dissolution of surface mineral crystals, that form first at the BWRO plant tail elements, by periodic exposure to the undersaturated feed solution. Automatic triggering of FFR was accomplished by integrating an Ex-situ scale observation detector (EXSOD) with the BWRO plant controller. The EXSOD system consisted of a small high pressure plate-and-frame RO cell, with its membrane surface digitally imaged in real-time, to monitor the onset and development of membrane mineral scaling. During normal feed flow (NFF) operation, the EXSOD monitored a concentrate side-stream from the BWRO plant tail element, signaling the BWRO plant controller to initiate FFR when the specified scaling threshold was reached. Once the plant feed flow was reversed, the EXSOD feed stream was switched from the BWRO plant concentrate to the plant's permeate in order to dissolve mineral crystals formed on the EXSOD membrane during NFF operation. Successful operation of automated FFR, whereby scale formation was prevented, required adjustment of the EXSOD operating conditions such that the saturation index in the EXSOD RO cell was at a level that would not result in scale detection significantly before or after scaling would occur in the RO plant. Although the onset of mineral scaling was detected at the level of appearance of the first observable mineral crystal, the results suggest that it would be more practical to trigger FFR based on a threshold that considers both the mineral crystal number density and fractional surface scale coverage. Current work is continuing to demonstrate the broad applicability of FFR mode of RO mineral scale-free operation (with reduced or no antiscalant addition) over a wide range of solution compositions and operating conditions.

Purpose: To investigate the neuroprotective effect of brimonidine following induction of ischaemic optic neuropathy in rodents (rAION). Methods: Mice were treated with an intraperitoneal injection of brimonidine 48, 24 or 0 h before rAION induction or eye drops for 5 days after rAION induction. Retinal ganglion cell (RGC) loss and expression of genes involved in the angiogenesis (vascular endothelial growth factor [VEGF], pigment epithelium-derived factor [PEDF], The epidermal growth factor homology domains-2 [Tie-2]), ischaemia (haem oxygense-1 [HO-1], hypoxia-inducible factor 1α[HIF-1α], endothelial nitric oxide synthase [eNOS]) and oxidative stress (superoxide dismutase-1 [SOD-1], glutathione peroxidase-1 [GPX-1]) response to ischaemic damage were compared with sham or rAION-untreated mice. Results: No RGC loss was detected in the brimonidine-treated mice. Effect of post-rAION eye drops: day 1 – no decrease in retinal mRNA levels of angiogenesis-related genes, increase in ischaemia- and oxidative stress-related genes except HIF-1α; day 3 – baseline or higher levels of oxidative and ischaemia-related genes except HIF-1α, increase in VEGF, decrease in PEDF; day 21 – no change in angiogenesis-related genes. Effect of pre-rAION injection: baseline levels of angiogenesis-related genes with all injection schedules; increase in ischaemia-related genes with 48-h and 0-h pretreatment; decrease in HO-1 and eNOS with 24-h pretreatment; increase in oxidative-related genes except GPX-1. In optic nerve tissue, HO-1, HIF-1α and SOD-1 decreased on day 1 after topical administration and were still below baseline on day 3. Conclusions: The increase in HO-1 associated with rAION is mitigated with brimonidine treatment, especially when administered intraperitoneally. Topical brimonidine apparently reduces VEGF, Tie-2, HIF-1α and GPX-1 expression on day 21. These results agree with published data and may have therapeutic implications for patients diagnosed with AION in the acute phase.

In this paper we present the synthesis and characterization of a new family of thio-ether-footed resorcin[4]arenes (2–4). Diffusion NMR was used to follow the self-assembly of 2–4 in CDCl3 and CHCl3 solutions. We found that all three molecules self-assemble into hexameric capsules. These capsules can accommodate both tertiary alkylamines and ammonium salts. From the diffusion NMR data we could conclude that the hexameric capsules of compounds 2–4 are of nearly equal stability and prevail in other organic solvents, such as dichloromethane and benzene but not in tetrahydrofuran (THF). By measuring the diffusion coefficients of 2–4 in different concentrations, we found that further aggregation, beyond the hexameric aggregates, is obtained, especially in the case of 2 at high concentrations. Different diffusion NMR techniques revealed that water molecules are part of the hexameric capsules of 2–4 in chloroform solutions. In addition diffusion NMR was used to examine the interactions of compounds 2–4 with gold nanoparticles in chloroform solution and provided an unequivocal evidence for the attachment of 2–4 to the surface of gold nanoparticles. No evidence was found for the formation of higher aggregates on the gold nanoparticles.

Thin poly(4-vinylpyridine) films terminally anchored onto nonporous inorganic oxide substrates were synthesized by aqueous phase reverse atom transfer radical graft polymerization (ATRGP). Surface initiators were immobilized on the inorganic substrate surface by chemically attaching glycidoxytrimethoxy silane onto the substrates followed by conversion of the glycidoxy silane into azobis silane by a reaction with 4,4′-azobis(4-cyanovaleric acid). Reverse ATRGP of 4-vinylpyridine onto the active surface azo sites was carried out in a 1-methyl-2-pyrrolidone/water solvent mixture using CuCl2/2,2′-bipyridine as the catalyst-ligand complex with initial monomer concentration [M]0 = 2.32M at 90°C. Controlled radical polymerization was achieved at catalyst to initiator molar ratios of 2 : 1 and 3 : 1, with a catalyst to ligand molar ratio of 1 : 2. Controlled polymerization was indicated by a first-order rate of polymerization kinetics, with respect to monomer conversion at the surface and in solution, the linear increase of the P4VP graft yield with time, and a low polydispersity index (PDI < 1.40). The highest graft yield of 8 mg/m2 was achieved at a 3 : 1 catalyst to initiator molar ratio which corresponded to a number-average molecular weight of 11,500 g/mol, surface density of 0.69 μmol/m2, and a polydispersity index of 1.28. AFM surface analysis of the grafted polymer films, prepared by reverse ATRGP of 4VP, revealed a decrease in the RMS surface roughness (RRMS = 1.04 nm) and feature size (feature diameter = 20–45 nm), relative to uncontrolled free radical graft polymerization (RRMS = 1.42 nm; feature diameter = 60–145 nm), thereby providing an additional indication that a denser and controlled reaction was achieved via reverse ATRGP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

In confined geometries, the MR signal attenuation obtained from single pulsed gradient spin echo (s-PGSE) experiments reflects the dimension of the compartment, and in some cases, its geometry. However, to measure compartment size, high q-values must be applied, requiring high gradient strengths and/or long pulse durations and diffusion times. The angular double PGSE (d-PGSE) experiment has been proposed as a means to extract dimensions of confined geometries using low q-values. In one realization of the d-PGSE experiment, the first gradient pair is fixed along the x-axis, and the orientation of the second gradient pair is varied in the X–Y plane. Such a measurement is sensitive to microscopic anisotropy induced by the boundaries of the restricting compartment, and allows extraction of the compartment dimension. In this study, we have juxtaposed angular d-PGSE experiments and simulations to extract sizes from well-characterized NMR phantoms consisting of water filled microcapillaries. We are able to accurately extract sizes of small compartments (5 μm) using the angular d-PGSE experiment even when the short gradient pulse (SGP) approximation is violated and over a range of mixing and diffusion times. We conclude that the angular d-PGSE experiment may fill an important niche in characterizing compartment sizes in which restricted diffusion occurs.

The PI3 K/AKT pathway is frequently activated in human cancer. Recently, a G to A point mutation (E17 K) was found in the pleckstrin homology domain of AKT1. We aimed to explore this mutation in cases of urothelial carcinoma. Using chip-based matrix-assisted laser desorption-time-of-flight (MALDI-TOF) mass spectrometer, AKT1 E17 K mutation was searched in 26 total RNA samples obtained from 26 patients known to have urothelial carcinoma. Mutation was found in one out of 26 (3.8%) patients – a 46 year old female with a low grade transitional cell carcinoma located to the lamina propria (Ta disease). Our finding is in line with previous studies showing AKT1 E17 K mutation to be rare. Yet, further studies are required to determine whether this mutation is indeed related to less aggressive disease and carries better prognosis.

This work focuses on the design and implementation of a nonlinear model-based control system on an experimental reverse-osmosis (RO) membrane water desalination system to address large set-point changes and variations in feedwater salinity. A dynamic nonlinear lumped-parameter model is derived using first-principles, and its parameters are computed from experimental data to minimize the error between model predictions and experimental RO system response. This model then is used as the basis for the design of a nonlinear control system, using geometric control techniques. The nonlinear control system is implemented on the experimental RO system, and its set-point tracking and disturbance rejection capabilities are successfully evaluated.

Model-predictive control algorithms are applied to a high capacity reverse osmosis (RO) membrane desalination process simulation that utilizes feed flow reversal in order to prevent and/or reverse scale crystal formation on the membrane surface. A dynamic non-linear model which incorporates feed concentration and membrane properties is used for simulation and demonstration of optimally controlled feed flow reversal. Before flow reversal can take place on a high capacity RO plant, the flow into the membrane unit must be carefully reduced to eliminate the risk of membrane module damage and unnecessary energy consumption. A cost function is formulated for the transition between the normal high flow steady-state operating point to a low flow steady-state operating point where it is safe to reverse the flow direction. Open-loop and closed-loop simulations demonstrate non-linear model-predictive control strategies that induce transition from the high-flow to low-flow steady-states in an optimal way while subjected to plant-model mismatch on the feed concentration, actuator magnitude and rate constraints, and sampled measurements.

The potential impact of coagulants on mineral scaling in reverse osmosis (RO) feed treatment of brackish water was assessed experimentally, with respect to calcium sulfate and barium sulfate scalin...

A neural network-based modeling approach with back-propagation and support vector regression algorithms was investigated as a mean of developing data-driven models for forecasting reverse osmosis (RO) plant performance and for potential use for operational diagnostics. The concept of plant “short-term memory” time-interval was introduced to capture the time-variability of plant performance since both a state of the plant model and standard time-series analyses for both flux decline and salt passage did not result in realistic predictive horizons for practical purposes. Past information of normalized permeate flux and salt passage were introduced as unique input variables along with process operating parameters to capture short-term plant performance variability. Sequential models, where the time-variation within each forecasting time-interval was also taken as input information, and marching forecasting models, where target values were predicted at fixed future times from past plant information, were developed. Models were trained, with normalized permeate flux and salt passage, for various model architectures, memory time-intervals and forecasting times using both back-propagation and support vector regression approaches. State of the plant models (without forecasting) were able to describe the relatively small permeate flux variations but were unable to capture salt passage trends (for any present time condition) since unsteady state phenomena could not be properly described without plant memory information. Forecasting of plant performance, with both sequential and marching models, yielded good predictive accuracy for short-term memory time-intervals in the range of 8–24 h for permeate flux and salt passage for forecasting times up to 24 h. Current work is ongoing to extend the approach for longer time scales and to incorporate data-driven forecasting models of RO plant into control strategies and process diagnostics.

Double pulsed gradient spin echo (d-PGSE) experiment has been recently suggested for detecting microscopic anisotropy in macroscopically isotropic samples. This sequence is complex and has many variables, including, intra alia, combinations of directions and amplitudes of the pulsed gradients, diffusion times in each of the encoding periods and the mixing time period. The effect of these experimental parameters of the d-PGSE sequence was studied in an array of water filled microcapillaries of micron diameters. We found that negative diffractions occur, as indeed predicted by recently published simulations. We also found differential effects of prolongation of the mixing time between collinear and orthogonal d-PGSE experiments. The d-PGSE experiment in the collinear direction perpendicular to the long axis of the cylinder exhibited a marked dependence on the mixing time, while the orthogonal d-PGSE experiment exhibited no such dependence at all. Interestingly, one of the most important predictions by the simulations was that the d-PGSE sequence could potentially discriminate between compartments of different sizes better than the single PGSE (s-PGSE) and it seems that our experimental results indeed corroborate these predictions.

Polymer layer growth by free radical graft polymerization (FRGP) and controlled nitroxide-mediated graft polymerization (NMGP) of polystyrene was achieved by atmospheric pressure hydrogen plasma surface activation of silicon. Kinetic polystyrene layer growth by atmospheric pressure plasma-induced FRGP (APPI-FRGP) exhibited a maximum surface-grafted layer thickness (125 A after 20 h) at an initial monomer concentration of [M] 0 = 2.62 M at 85 degrees C. Increasing both the reaction temperature ( T = 100 degrees C) and initial monomer concentration ([M] 0 = 4.36 M) led to an increased initial film growth rate but a reduced polymer layer thickness, due to uncontrolled thermal initiation and polymer grafting from solution. Controlled atmospheric pressure plasma-induced NMGP (APPI-NMGP), using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), exhibited a linear increase in grafted polystyrene layer growth with time due to controlled surface graft polymerization as well as reduced uncontrolled solution polymerization and polymer grafting, resulting in a polymer layer thickness of 285 A after 60 h at [TEMPO] = 10 mM, [M] 0 = 4.36 M, and T = 120 degrees C. Atomic force microscopy (AFM) surface analysis demonstrated that polystyrene-grafted surfaces created by APPI-NMGP exhibited a high surface density of spatially homogeneous polymer features with a low root-mean-square (RMS) surface roughness ( R rms = 0.36 nm), similar to that of the native silicon surface ( R rms = 0.21 nm). In contrast, polymer films created by APPI-FRGP at [M] 0 = 2.62 M demonstrated an increase in polymer film surface roughness observed at reaction temperatures of 85 degrees C ( R rms = 0.55 nm) and 100 degrees C ( R rms = 1.70 nm). The present study concluded that the current approach to APPI controlled radical polymerization may be used to achieve a grafted polymer layer with a lower surface roughness and a higher fractional coverage of surface-grafted polymers compared to both conventional FRGP and APPI-FRGP.

q-Space diffusion MRI (QSI) provides a means of obtaining microstructural information about porous materials and neuronal tissues from diffusion data. However, the accuracy of this structural information depends on experimental parameters used to collect the MR data. q-Space diffusion MR performed on clinical scanners is generally collected with relatively long diffusion gradient pulses, in which the gradient pulse duration, delta, is comparable to the diffusion time, Delta. In this study, we used phantoms, consisting of ensembles of microtubes, and mathematical models to assess the effect of the ratio of the diffusion time and the duration of the diffusion pulse gradient, i.e., Delta/delta, on the MR signal attenuation vs. q, and on the measured structural information extracted therefrom. We found that for Delta/delta approximately 1, the diffraction pattern obtained from q-space MR data are shallower than when the short gradient pulse (SGP) approximation is satisfied. For long delta the estimated compartment size is, as expected, smaller than the real size. Interestingly, for Delta/delta approximately 1 the diffraction peaks are shifted to even higher q-values, even when delta is kept constant, giving the impression that the restricted compartments are even smaller than they are. When phantoms composed of microtubes of different diameters are used, it is more difficult to estimate the diameter distribution in this regime. Excellent agreement is found between the experimental results and simulations that explicitly account for the use of long duration gradient pulses. Using such experimental data and this mathematical framework, one can estimate the true compartment dimensions when long and finite gradient pulses are used even when Delta/delta approximately 1.

Diagnostic analysis of reverse osmosis membranes that were fed with Western treatment plant (WTP) recycled water was investigated by both thermodynamic calculations and laboratory experiments in order to predict the feasibility of RO desalting for WTP. The thermodynamic calculations suggested that RO recoveries of 80–85% were feasible with careful control of feed water pH and the use of chemical additives such as antiscalants and chelating agents, it also predicted the major minerals of concern to be silica, calcium fluoride, calcium carbonate, and calcium phosphate. Following the thermodynamic simulations, diagnostic laboratory experiments were undertaken. The experiments showed that the major contributor to scale formation was indeed calcium phosphate and possibly another calcium based compound, which was strongly suspected to be calcium carbonate. Based on previously published literature that indicated anti-scalants did not substantially decrease the scaling effect of calcium phosphate and laboratory tests that indicated controlling the pH to 6.4 in the feed water dramatically reduced scaling formation, it was suggested that the feed water could be controlled by pH adjustments only. Inter-stage pH correction was suggested as an optional technique to enhance the overall water recovery to above 95%.

Advances in highly permeable reverse osmosis (RO) membranes have enabled desalting operations, in which it is practically feasible for the applied pressure to approach the osmotic pressure of the exit brine stream. However, energy cost remains a major contributor to the total cost of water produced by RO membrane desalination. Reduction of the overall cost of water production represents a major challenge and, in the present work, various elements of water production cost are evaluated from the viewpoint of optimization, with respect to various costs (energy, membrane area and permeability, brine management, and pressure drop), as well as the important thermodynamic cross-flow constraint, utilization of energy recovery devices, and operational feed and permeate flow rate constraints. More specifically, in the present study, an approach to the optimization of product water recovery at pressures that approach the osmotic pressure of the exit brine stream is presented via several simple RO process models that...

Model-based control and monitoring such as feed-forward/feedback control, fault detection and isolation (FDI), and fault-tolerant control (FTC) techniques that utilize Lyapunov-based control laws are implemented on a high recovery reverse osmosis desalination plant model. A detailed mathematical model of a high recovery reverse osmosis plant is developed. This model incorporates the large spatial variations of concentration and flow rate that occur in membrane units during high recovery operation. Bounded nonlinear feedback and feed-forward controllers are developed and applied to this system. The application of these controllers with FDI and FTC is demonstrated in the context of a high recovery reverse osmosis process simulation. The first set of simulations demonstrates the ability to compensate for the effects of large time-varying disturbances in the feed concentration on specific process outputs with and without feed-forward control. The second set of simulations demonstrates the ability of FDI and F...

BRCA1/BRCA2 germline mutations substantially increase breast and ovarian cancer risk, yet penetrance is incomplete. We hypothesized that germline epigenetic gene silencing may affect mutant BRCA1/2 penetrance. To test this notion, we determined the methylation status, using methylation-specific quantitative PCR of the promoter in putative modifier genes: BRCA1, BRCA2, ATM, ATR and P53 in Jewish BRCA1/BRCA2 mutation carriers with (n = 41) or without (n = 48) breast cancer, in sporadic breast cancer (n = 52), and healthy controls (n = 89). Promoter hypermethylation was detected only in the BRCA1 promotor in 5.6-7.3% in each of the four subsets of participants, regardless of health and BRCA1/2 status.Germline promoter hypermethylation in the BRCA1 gene can be detected in about 5% of the female Israeli Jewish population, regardless of the BRCA1/2 status. The significance of this observation is yet to be determined.

Stem cell-based treatment is a promising frontier for neurodegenerative diseases. We propose a novel protocol for inducing the differentiation of rat mesenchymal stem cells (MSCs) toward neurotrophic factor (NTF)-secreting cells as a possible neuroprotective agent. One of the major caveats of stem cell transplantation is their fate post-transplantation. To test the viability of the cells, we tracked the transplanted cells in vivo by magnetic resonance imaging (MRI) scans and validated the results by histology. MSCs went through a two-step medium-based differentiation protocol, followed by in vitro characterization using immunocytochemistry and immunoblotting analysis of the cell media. We examined the migratory properties of the cells in the quinolinic acid (QA)-induced striatal lesion model for Huntington's disease. The induced cells were labeled and transplanted posterior to the lesion. Rats underwent serial MRI scans to detect cell migration in vivo. On the 19th day, animals were sacrificed, and their brains were removed for immunostaining. Rat MSCs postinduction exhibited both neuronal and astrocyte markers, as well as production and secretion of NTFs. High-resolution two-dimensional and three-dimensional magnetic resonance images revealed that the cells migrated along a distinct route toward the lesion. The in vivo MRI results were validated by the histological study, which demonstrated that phagocytosis had only partially occurred and that MRI could correctly depict the status of the migrating cells. The results show that these cells migrated toward a QA lesion and therefore survived for 19 days post-transplantation. This gives hope for future research harnessing these cells for treating neurodegenerative diseases. Disclosure of potential conflicts of interest is found at the end of this article.

Organic solute permeation, sorption, and rejection by reverse osmosis membranes, from aqueous solutions, were studied experimentally and via artificial neural networks (ANN)-based quantitative structure–property relations (QSPR), for a set of fifty organic compounds for polyamide and cellulose acetate membranes. Membrane solute sorption and passage for dead-end filtration model experiments were quantified based on radioactivity measurements for radiolabeled compounds in the feed, permeate and the membrane, while solute rejection was determined from a mass balance on the permeated solution volume. Artificial neural networks-based quantitative structure–property relations models were developed for the organic passage ( P ), sorbed ( M ) and rejected ( R ) fractions using the most relevant set of molecular descriptors selected from a pool of 45 molecular descriptors by means of a correlation-based feature selection method and self-organizing maps (SOM). The analysis included pre-screening with principal components analysis and SOM of the chemical domain for the study chemicals as defined by chemical descriptors to identify the applicability domain and chemical similarities. The QSPR models predicted the P and M mass fractions within the range of the standard deviations of measurements for the experimental data set of fifty compounds. Mass balance closure (requiring that M , P and R sum to unity) was satisfactory for the experimental data set of fifty compounds and for an external set of 144 test chemicals, which were not included in the model development. Somewhat higher prediction errors were encountered for a few chemicals that were not well represented within the present chemical domain. The quality of the QSPR/NN models developed suggests that there is merit in extending both the present compound database and the present approach to develop a comprehensive tool for assessing organic solute behavior in RO water treatment processes.

The development of calcium sulfate dihydrate (gypsum) mineral scale in reverse osmosis (RO) membrane desalting was investigated by direct real-time observation of crystal growth. Gypsum scaling studies were conducted in a specially modified plate-and-frame reverse osmosis cell fitted with an optical window, with dark-field membrane lighting arrangement within the membrane cell to enhance crystal boundaries and allow recording of digital surface images magnified through an optical microscope. The evolution of the surface number density (SND) of gypsum crystals resembled a sigmoidal population growth process with an increasing rate of crystal formation at higher solution supersaturation (with respect to gypsum) at the membrane surface. The rate of formation of new crystals declined as the surface scale coverage increased, with surface scale progressing by diffusion-controlled growth of existing crystals as the gypsum crystal SND approached its plateau. The apparent crystallization induction time (i.e., observation time for the appearance of surface crystals) decreased with increased supersaturation, with single crystals growth reasonably characterized by a diffusion-growth model and a single crystal fluid mass transfer coefficient that was generalized by a Sherwood number type correlation. The present approach provides a convenient method of characterizing the kinetics of gypsum scale formation via quantification of single crystal mass transfer coefficient and evolution of the crystal SND. Such information can guide the development of comprehensive RO membrane scale formation models and characterization of mineral scaling propensities of RO membranes and source water where mineral salt scaling is of concern.