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An uncharged, water‐soluble per‐ethylene‐glycol pillar[5]arene derivative (1) was synthesized and its aggregation mode, host‐guest chemistry in water and extraction ability was explored. Compound 1 is a liquid at room temperature; in water, limited self‐aggregation occurred at high concentrations as deduced from diffusion NMR and dynamic light scattering. Compound 1 forms pseudo‐rotaxane‐like 1 : 1 host‐guest complexes with 1,ω‐di‐substituted alkanes with association constants on the order of 103–104 m −1. Interestingly, NMR experiments showed that the guest location relative to the host ring system differs among the different complexes. In proof‐of‐concept experiments, compound 1 was shown to extract structurally related organic compounds from benzene into water with significant selectivity. Compound 1, which is a liquid at room temperature and has only limited interactions with its side arms, can, in principle, be regarded as a complement to or as a kind of type I porous liquid., A liquid host based on a per‐ethylene‐glycol pillar[5]arene derivative (1) was prepared and its self‐aggregation, host‐guest chemistry in water and extraction capabilities were studied and evaluated. 1 forms pseudo‐rotaxane‐like complexes with 1,ω‐di‐substituted alkanes, showing Ka values in the range of 103–104 M−1. Host 1 can extract such alkanes with 6–7 fold selectivity and since the interaction with its rim side‐chains is weak, 1 can be regarded as a complement to or as a sort of type 1 porous liquid.

NMR has been instrumental in studies of both the structure and dynamics of molecular systems for decades, so it is not surprising that NMR has played a pivotal role in the study of host-guest complexes and supramolecular systems. In this mini-review, selected examples will be used to demonstrate the added value of using (multiparametric) NMR for studying macrocycle-based host-guest and supramolecular systems. We will restrict the discussion to synthetic host systems having a cavity that can engulf their guests thus restricting them into confined spaces. So discussion of selected examples of cavitands, cages, capsules and their complexes, aggregates and polymers as well as organic cages and porous liquids and other porous materials will be used to demonstrate the insights that have been gathered from the extracted NMR parameters when studying such systems emphasizing the information obtained from somewhat less routine NMR methods such as diffusion NMR, diffusion ordered spectroscopy (DOSY) and chemical exchange saturation transfer (CEST) and their variants. These selected examples demonstrate the impact that the results and findings from these NMR studies have had on our understanding of such systems and on the developments in various research fields.

Supramolecular systems in water are of paramount importance and those based on hydrogen bonds are both intriguing and scarce. Here, after studying the peculiar host-guest complexes formed between per-dimethylamino-pillar[5]arene (1) and the bis-sulfonates 2 a-c, we describe the formation of the first hydrogen-bond-based supramolecular pentagonal boxes (SPBs), which are stable in water. These pH-responsive SPBs are constructed from 1 as a body, benzene polycarboxylic acids 3 a,b as lid compounds, and 2 a-c as guests. We demonstrate that encapsulation of 2 a-c in pillar[5]arene 1 and in the highly stable water-soluble SPBs, that is, 1(3 a)2 and 1(3 b)2 , is both temperature and pH dependent and, quite interestingly, depends, on the nature of the lid compounds used for capping the boxes even at high pH. We also highlight the difference in the 1 H NMR characteristics of 2 b and 2 c in the cavity of 1 and the SPBs.

Tethered poly(acrylic acid) (PAA) chains, synthesized onto polysulfone (PSf) surfaces, were characterized with respect to surface topography and chain characteristics via AFM force spectroscopy. The tethered PAA chains were synthesized by surface activation with an impinging atmospheric pressure plasma stream (He, He/O2 and He/H2), followed by free-radical acrylic acid graft polymerization. The number average molecular weight of the tethered PAA chains was estimated to be of in the range of ∼13,000–35,000 with chain-chain separation of 1.5–2.4 nm. Deionized and high salinity water contact angles for the PAA-PSf surfaces were in the range of ∼ 29–38°, indicating hydrophilic surfaces, relative to 80° contact angle for the native hydrophobic PSf surface. In DI water the tethered PAA chains had significantly greater chain extension than in a high salinity aqueous environment. Ultrafiltration fouling stress tests with alginic acid in a high salinity water and post cleaning with non-saline water demonstrated permeability restoration of up to 90–100% for a PAA-PSf membrane relative to 50–70% for the native PSf membrane. The present study suggests the merit of exploring and optimizing surface modification of membranes for saline water filtration to reduce irreversible fouling and improve cleaning effectiveness using non-saline water.

Diffusion NMR is a useful analytical tool for the characterization of supramolecular systems in solution. In this mini-review, after a short introduction and some methodological tips, we discuss, from a personal point of view, the use of diffusion NMR in the study of calixarene- and other arene-based supramolecular systems. We will demonstrate, through selected examples, how diffusion has been used to study, in solution, the structures and other characteristics of supramolecular systems based on calixarene and related systems ranging from different complexes and aggregates to molecular capsules and to supramolecular oligomers and polymers.

Two-component supramolecular organogels based on per-carboxylato- and per-amino pillar[6]arenes (2 and 4a–c) were prepared for the first time, and found to display very different characteristics as compared to those displayed by the corresponding pillar[5]arene derivatives (1 and 3a–c). Pillar[6]arenes derivatives, in contrast to pillar[5]arene derivatives, do not form organogels in alcoholic solutions and the formed gels in chlorinated solvents are, generally, more fragile. We analyzed the gelation ability of all the pairs between 1, 2, 3a–c and 4a–c, several three-component mixtures in 1 : 1 : 1 and 2 : 1 : 1 ratios, as well as four-component mixtures in ∼10 : 1 CDCl3 : DMSOd6 solutions. The obtained results clearly show that shape complementarity is an important determinant of gel formation in these supramolecular pillar[n]arene-based organogels. We also found that shape directed molecular sorting occurs in the gelation process of these two-component supramolecular organogels.

The influence of surface modification of zirconia (ZrO2) membrane with tethered poly(vinyl pyrrolidone) (PVP) chains was evaluated with respect to the impact of pH and ionic strength on hydraulic resistance and fouling resistance in the filtration of bovine serum albumin (BSA) and lysozyme (Lys) as model protein foulants. The tethered PVP surface layer led to membrane permeability and fouling propensity that were responsive to both pH and ionic strength. The PVP-modified membrane (PVP-ZrO2) hydraulic resistance increased by up to ~48% over a pH range of 6–11, but with no discernible impact at lower pH. Membrane hydraulic resistance was virtually unaffected by ionic strength over the 0.001–1 M range. However, reversible foulant cake resistance in BSA and Lys solution filtration increased with elevated ionic strength, owing in part to the weakening of protein–protein repulsion. Irreversible BSA and Lys fouling was affected by the operational pH relative to the protein isoelectric point (IEP) and reduced under conditions of chain swelling. Irreversible membrane fouling resistance for both proteins was significantly lower, by ~11–49% and 18–74%, respectively, for the PVP-ZrO2 membrane relative to the unmodified ZrO2 membrane. The present results suggest the merit of further exploration of fouling reduction and improvement of membrane cleaning effectiveness via tuning pH and ionic strength triggered conformational responsiveness of the tethered target polymer layer.

A deep cavitand binds long-chain trans,trans- and trans,cis-bis-formamide isomers in water solution giving a pair of caviplexes in a ca. 60:40 ratio. Both caviplexes display in/out guest exchange dynamics that are slow on the 1 H NMR chemical shift timescale, but fast on the EXSY timescale. We apply diffusion-ordered NMR spectroscopy (DOSY) to characterize the caviplexes. On the diffusion timescale, the guest in/out exchange processes feature intermediate dynamics allowing the assessment of their kinetic stabilities. We found that the trans,cis-bis-formamide isomers form kinetically more stable caviplexes than the trans,trans-counterparts. We also show that the kinetic stabilities of the bis-formamide caviplexes relate well with their relative thermodynamic stabilities. Fortunately, the tuning of the DOSY parameters allowed the observation of the exchange dynamics as slow processes on the experiment timescale.

This paper presents methodology, concept and results of the WateReuse Foundation project WFR – 09 – 06b when developing a high pressure membrane, reverse osmosis (RO) and nanofiltration (NF) online membrane integrity testing (MIT) technique. The use of pressure-driven membrane processes, particularly RO, has grown significantly over the past few decades in water treatment and reuse applications to safeguard water supplies against harmful pathogens and impurities. In principle, RO membranes should provide a complete physical barrier to the passage of nanosize pathogens (e.g., enteric viruses). However, in the presence of imperfections and/or membrane damage, membrane breaches as small as 20 to 30 nm can allow enteric viruses to pass through the membrane and contaminate the product water stream, thereby posing a potential health hazard that is of particular concern for potable water production. This project was focused on evaluating a pulsed-marker membrane integrity monitoring (PM-MIMo) approach for RO processes on the basis of the use of a fluorescent marker. The monitoring approach employs pulsed dosing (via a precision metering pump) of a marker into the RO feed stream coupled with online marker concentration monitoring in the RO permeate by an inline spectrofluorometer. Membrane integrity is then inferred on the basis of real-time analysis of the marker permeate time − profile concentration in response. The basic concept of the PM-MIMo approach for detecting membrane breaches was successfully demonstrated, by comparing intact and damaged membranes, in a series of experiments using a diagnostic plate-and-frame RO system and spiral-wound RO pilot system. Results of the developed technique are presented in the project report to allow the industry to consider adopting this technique for RO/NF online integrity monitoring.

Macrocyclic host structures for generating transiently bound 129 Xe have been used in various ultra-sensitive NMR and MRI applications for molecular sensing of biochemical analytes. They are based on hyperpolarized nuclei chemical exchange saturation transfer (Hyper-CEST). Here, we tested a set of water-soluble pillar[5]arenes with different counterions in order to compare their potential contrast agent abilities with that of cryptophane-A (CrA), the most widely used host for such purposes. The exchange of Xe with such compounds was found to be sensitive to the type of ions present in solution and can be used for switchable magnetization transfer (MT) contrast that arises from off-resonant pre-saturation. We demonstrate that the adjustable MT magnitude depends on the interplay of saturation parameters and found that the optimum MT contrast surpasses the CrA CEST performance at moderate saturation power. Since modification of such water-soluble pillar[5]arenes is straightforward, these compounds can be considered a promising platform for designing various sensors that may complement the field of Xe HyperCEST-based biosensing MRI.

Rationally designed two-component supramolecular organogels based on multiple chemical interactions between percarboxylato- and peramino-pillararenes are described. Mixing low concentration solutions (

Bis-resorcin[4]arene 2 connected by its lower rims was synthesized via click chemistry and found, by diffusion NMR, to self-assemble quantitatively, despite the different alternatives, into hexameric capsules reminiscent of the well-characterized hexameric capsule of resorcin[4]arene 1. The hexameric capsules of the flexible bis-resorcin[4]arene 2 prevail in apolar organic solvents and can, as expected, encapsulate quite well ammonium salts, demonstrating that spontaneous self-assembly into hexameric capsules is a general characteristic of such systems.

Hydraulic permeability and molecular weight cutoff (MWCO) performance tuning of polysulfone (PSf) ultrafiltration (UF) membrane was attained via surface modification with a tethered layer of poly(acrylic acid) (PAA). Surface nano-structured (SNS) PAA layer was synthesized onto base PSf UF membranes by atmospheric pressure plasma (APP) surface activation followed by graft polymerization (GP) of acrylic acid (AA). Through a systematic study, it was shown that effective SNS-PAA-PSf UF membrane performance tuning was feasible by adjustments of APP and graft polymerization conditions. It was shown, for the first time, that SNS-PAA-PSf membranes can be synthesized with a range of hydraulic permeability (spanning a factor of 1.1–2.6 in magnitude) for a given MWCO, or a range of MWCO (spanning a factor of 1.5–2.3 in magnitude) for a given hydraulic permeability, thereby overcoming the hydraulic permeability-MWCO tradeoff.

Silica scaling of RO membranes was evaluated via real-time direct surface imaging demonstrating a capability for detecting the onset of silica scale formation and its evolution. Silica scaling was detected significantly earlier than by traditional flux decline measurements. The observed rate of silica particle nucleation followed classical nucleation theory while the growth of individual silica particles, at the early stages of silica scaling, was governed by diffusional growth. SEM and optical images of the membrane surface suggest that silica scaling occurs through the formation of both primary silica particles and their agglomerates (~1–30 µm), as well as a gel-like silica film embedded with silica particles both of which contribute to permeate flux decline. At low silica saturation index at the membrane surface (SIm≤1.93) silica gel film formation resulted in a smoother and less porous film than at higher silica saturation (SIm≥2.72). At the higher silica saturation levels (SIm=2.72–3.50), silica scaling resulted in larger observed particles as well as rapid permeate flux decline. The silica scale layer thickness was in the range of ~0.1–3.5 µm, with surface roughness being higher by a factor of 2.6–8.3 relative to the native membrane. Results of the present study suggest that there is merit in exploring the application of the present approach for early detection and monitoring of silica scaling in RO plants in support of strategies for silica scale mitigation.

Real-time self-adaptive approach to in-line UF coagulant dosing was developed and field demonstrated for integrated UF-RO seawater desalination. A novel coagulant dose controller was designed and successfully implemented in a pilot UF-RO seawater desalination plant. The coagulant controller, which tracks the UF resistance during filtration and backwash, adjusts coagulant dose to the UF feed with the objective of reducing the incremental cycle-to-cycle UF post-backwash (PB) resistance change (i.e., Δn). Real-time tracking the above UF resistance metrics, as well as the rate of change of Δn with coagulant dose, enabled the controller to quantify the progression of both irreversible fouling and UF backwash effectiveness. The above information was then utilized by the controller to make the appropriate coagulant adjustment. Field tests of the proposed self-adaptive coagulant dosing approach demonstrated measurable coagulant dose reduction while maintaining robust UF operation even during periods of both mild and severe water quality degradation. The approach to real-time coagulant dose control developed in the present work should be suitable for both seawater and brackish water UF treatment and has the potential of providing both effective UF operation as well as reduction in coagulant use.

Modification of inorganic oxide surfaces is used in a variety of practical applications and in the study of interfacial phenomena. There are a multitude of surface modification methods, including modification by reactive polymer interlayers, diblock copolymerization, and polymer adsorption. Although various polymers can be used to modify an inorganic oxide substrate, this chapter focuses on poly(vinylpyrrolidone) (PVP) and poly(vinyl acetate). PVP grafting can be used to form a nontoxic surface that possesses superior hydrophilic and biocompatible properties. Free-radical graft polymerization in solution is relatively simple to carry out experimentally. The grafted polymer is covalently bonded to the surface through two concurrent mechanisms: polymer grafting and graft polymerization. Surface pretreatment is a crucial step which determines the surface activity for the subsequent graft polymerization. The use of vinyl alkoxysilanes with two or three alkoxy groups is particularly useful when the graft polymerization process is conducted in an aqueous solution.

Significance Many studies have investigated secondary formamides as mixtures of cis and trans isomers. They are widespread in nature, but relatively low energetic barriers to interconversion prevent the isolation and characterization of the pure isomers. Here, we determine hydrophilic differences between the isomers by binding in a water-soluble, synthetic molecular container. The container offers a range of environments from hydrophilic to hydrophobic and distinguishes subtle differences in the polarities of formamide isomers. Using NMR methods, we find that cis formamides are more hydrophobic than the corresponding trans isomers. The conclusion holds for diformamides, where we staged an intramolecular competition between cis and trans formamides within the container. Stable and isolable compounds are not required for the determination with this method.

We describe the preparation of the first water-soluble pH-responsive supramolecular hexagonal boxes (SHBs) based on multiple charge-assisted hydrogen bonds between peramino-pillar[6]arenes 2 with the molecular "lid" mellitic acid (1 a). The interaction between 2 and 1 a, as well as the other "lids" pyromellitic and trimesic acids (1 b and 1 c, respecively) were studied by a combination of experimental and computational methods. Interestingly, the addition of 1 a to the complexes of the protonated form of pillar[6]arene 2, that is, 3, with bis-sulfonate 4 a or 4 b, immediately led to guest escape along with the formation of closed 1 a2 2 supramolecular boxes. Moreover, the process of the openning and closing of the supramolecular boxes along with threading and escaping of the guests, respectively, was found to be reversible and pH-responsive. This study paves the way for the easy and modular preparation of different SHBs that may have myriad applications.

Ultrafiltration as a pretreatment for RO feedwater with enhanced UF backwash, which combines continuous with pulse backwash, was investigated in a novel UF-RO process integration. Direct supply of RO concentrate to the UF module served for UF backwash which was further enhanced with pulse backwash generated using bladder-type hydraulic accumulators. Model analysis of the hydraulic accumulator operation, which was validated via a series of field experiments, demonstrated a capability for accumulator charging directly from the RO concentrate stream within a period of 30–40 s. Moreover, pulse backwash over a short period (~5 s) which was added to the continuous UF backwash (directly from the RO brine stream), enabled peak UF backwash flux up to a factor of 4.2–4.6 higher than the normal filtration flux. The above mode of UF operation with multiple consecutive backwash pulses was more effective than with a single pulse, while inline coagulation further increased the UF performance. Relatively long-term field operation (over eight days where) of the UF-RO system with self-adaptive triggering of UF backwash, whereby the number of consecutive pulses increased when a higher membrane fouling resistance was encountered, was highly effective in enabling stable UF operation over a wider range of water quality conditions and without the need for chemical cleaning. These encouraging results suggest that direct UF-RO integration with enhanced pulse UF backwash is an effective approach for dead-end UF filtration without sacrificing water productivity.

Reverse osmosis (RO) polyamide (PA) membrane integrity loss, performance degradation, and alteration of surface properties due to exposure to chlorine were evaluated experimentally via a fluorescent marker (uranine) based method, water permeability and salt flux measurements, and surface characterization via XPS, AFM and contact angle measurements. Membrane exposure to chlorine (4–200 mg/L NaOCl solutions) revealed that although membrane surface roughness increased with chlorine exposure intensity (ppm-h), surface hydrophilicity increased as inferred by the decline (up to 5.2–9.6%) of the surface energy of hydration. Comparative analysis of marker transport for membranes that have undergone chlorine exposure of 125–2000 ppm-h demonstrated that the membrane marker permeability coefficient (B) increased by up to a factor of ~5 relative to the intact membrane. While the severity of membrane integrity loss/performance degradation correlated to a reasonable degree with ppm-h of chlorine exposure, the severity of membrane integrity loss, at the same chlorine ppm-h, was greater for higher exposure concentration. Membrane integrity loss, over the same exposure levels, was quantified by an equivalent cylindrical breach that was in the range of about 14–40 µm, increasing in size with the intensity of chlorine exposure.

Angular double-pulsed-field gradient (d-PFG) MR methodology is increasingly used to non-invasively obtain pore sizes in opaque chemical and biological systems. In such MR experiments, the angular dependency of the signal at zero mixing time, through modeling, can be used to extract the pore size. In many systems not only the pore sizes but also their directions are of importance. Before applying d-PFG NMR to complex systems, it is of value to challenge the ability of the methodology to extract these microstructural parameters in samples where the ground truth is known. In the present study we explored whether modeling of the signal in angular d-PFG NMR experiments at zero mixing time, can simultaneously provide the size and the direction of tilted compartments with little prior knowledge. We showed that the angular d-PFG MR methodology enables simultaneous extraction of the pore size and the direction of mono-dispersed phantoms and of phantoms where the restricted compartments have different pore sizes. However, we found that in phantoms with two or more pore sizes, only averaged pore sizes were extracted for large azimuthal and polar angles.

Tetraalkylammonium salts were found, contrary to literature reports, to be encapsulated into hexameric capsules of pyrogallol[4]arene in benzene solution. The guest affinity depended on the length of the alkyl chain, the counteranion, the solvent used, the ammonium concentration, and most importantly, the pyrogallol[4]arene to ammonium salt ratio. At high ammonium salt to pyrogallol[4]arene ratios no encapsulation was observed, presumably since the high salt destabilized the formed hexamers.

Labeling of smart PEG–dendron hybrids with fluorinated groups transformed their assemblies into enzyme-responsive micellar probes for 19F-magnetic resonance (MR). Two distinct labeling approaches were used to study the ability of these smart hybrids to be turned OFF at the assembled micellar state and to turn ON their 19F-MR signal upon enzymatic activation.

Polyamide (PA) thin film composite (TFC) BWRO and SWRO membranes were surface nano-structured (SNS) with tethered hydrophilic poly(acrylic acid) (PAA) layers. BWRO and SWRO membranes having water (Lp) and salt (B) permeability coefficients in the ranges of 2.3–3.4 L m−2 h−1·bar−1 and 0.15–0.54 L m−2 h−1, respectively, were utilized as base membranes onto which tethered PAA layers were synthesized via acrylic acid (AA) graft polymerization (GP), post-membrane surface activation with atmospheric pressure plasma (APP). Both APP surface activation and GP conditions impacted SNS-PAA-PA membrane performance evaluated in terms of the membrane Lp and B parameters. Surface structuring with a tethered PAA layer enabled tuning of membrane performance (in terms of Lp and B) to achieve water/salt selectivity (evaluated as Lp:B ratio) that was significantly higher (by up to 56%) relative to the base PA membranes. Depending on APP surface activation and AA graft polymerization conditions, membranes could be tuned to have essentially the same salt rejection over a range of permeability or a given permeability over a range of salt rejection. It was also shown that a membrane performance could be achieved that overcomes the permselectivity tradeoff.

The feasibility of wellhead water treatment in small communities for nitrate removal and salinity reduction via a flexible high recovery RO system was evaluated through analysis of treatment options, laboratory and onsite field tests. In small remote communities that rely on septic systems for residential wastewater treatment, discharge of the RO residual stream (containing nitrate) to the community septic tank is shown to be a feasible option. It is demonstrated that RO treatment with a system that employs partial concentrate recycle, integrated with a pressure intensifier, enabled the use of a relatively low-pressure feed pump while allowing high recovery operation. The approach of integrating RO treatment into existing community small water systems is demonstrated to be suitable for providing effective nitrate removal and salinity reduction over wide range of nitrate and salinity levels, while meeting community water demand and regulatory water quality requirements.

The use of 2D finite element CFD model and the common film model (FM) for analysis of FO performance data was examined to assess the merits of conclusions derived from the above approaches regarding characterization of membrane and support layer resistances to water and salt permeation. The FM model leads to estimation of porous layer resistivity (K) that implies tortuosity/porosity ratio that is significantly higher than is physically attainable for typical membrane porous supports. Comparative FO data analysis with the 2D CFD model and FM approximation reveals that the latter approach overestimates (by an order of magnitude and greater) the significance of the permeation resistance of the FO membrane support layer. It is also shown that membrane (water and solute) permeabilities extracted from FO operation in the RO mode (FO/RO) are significantly higher than obtained from direct analysis of FO performance data via detailed 2D CFD modeling. The present analysis suggests that improvements in FO water permeability are more likely to emerge from developing higher permeability membrane skin and improved channel hydrodynamics (to decrease external concentration polarization) rather than from more permeable and thinner membrane support layer as has been asserted in various studies.

Stejskal and Tanner's ingenious pulsed field gradient design from 1965 has made diffusion NMR and MRI the mainstay of most studies seeking to resolve microstructural information in porous systems in general and biological systems in particular. Methods extending beyond Stejskal and Tanner's design, such as double diffusion encoding (DDE) NMR and MRI, may provide novel quantifiable metrics that are less easily inferred from conventional diffusion acquisitions. Despite the growing interest on the topic, the terminology for the pulse sequences, their parameters, and the metrics that can be derived from them remains inconsistent and disparate among groups active in DDE. Here, we present a consensus of those groups on terminology for DDE sequences and associated concepts. Furthermore, the regimes in which DDE metrics appear to provide microstructural information that cannot be achieved using more conventional counterparts (in a model-free fashion) are elucidated. We highlight in particular DDE's potential for determining microscopic diffusion anisotropy and microscopic fractional anisotropy, which offer metrics of microscopic features independent of orientation dispersion and thus provide information complementary to the standard, macroscopic, fractional anisotropy conventionally obtained by diffusion MR. Finally, we discuss future vistas and perspectives for DDE.

Real-time membrane integrity monitoring is critically needed in order to ensure that reverse osmosis (RO) treatment and desalination processes provide a reliable barrier against the passage of pathogens for potable reuse applications. A pulsed marker membrane integrity monitoring (PM-MIM) method was developed for real-time assessment of RO membrane integrity. The sensitivity of the PM-MIM method was evaluated, using a fluorescent molecular marker, in a plate-and-frame RO (PFRO) membrane system with intact and compromised membranes (induced mechanically and via chemical oxidation). Analysis of the marker permeate concentration–time profiles, in response to a controlled marker feed pulse, allowed unambiguous detection of marker enhanced passage, which was indicative of membrane integrity loss. The PM-MIM approach, which is capable of demonstrating log removal value (LRV) above 4 for a fluorescent molecular marker (smaller in size than pathogens) should be suitable for providing a conservative estimate of pathogens LRV. However, regulatory acceptability of the present real-time PM-MIM approach will undoubtedly require long-term field evaluation in RO plants in order to establish the level of confidence to satisfy regulatory requirements for RO use in potable water reuse applications.

Quantitative structure-activity relationships (QSARs) were developed, for cellular uptake of nanoparticles (NPs) of the same iron oxide core but with different surface-modifying organic molecules, based on linear and non-linear (epsilon support vector regression (e-SVR)). A linear QSAR provided high prediction accuracy of R 2 =0.751 (coefficient of determination) using 11 descriptors selected from an initial pool of 184 descriptors calculated for the NP surfacemodifying molecules, while a e-SVR based QSAR with only 6 descriptors improved prediction accuracy to R 2 = 0.806. The linear and e-SVR based QSARs both demonstrated good robustness and well spanned applicability domains. It is suggested that the approach of evaluating pertinent descriptors and their significance, via QSAR analysis, to cellular NP uptake could support planning and interpretation of toxicity studies as well as provide guidance for the tailor-design NPs with respect to targeted cellular uptake for various applications.

Cellular association of nanoparticles (NPs) in biological fluids is affected by proteins adsorbed onto the NP surface, forming a "protein corona", thereby impacting cellular bioactivity. Here we investigate, based on an extensive gold NPs protein corona dataset, the relationships between NP-cell association and protein corona fingerprints (PCFs) as well as NP physicochemical properties. Accordingly, quantitative structure-activity relationships (QSARs) were developed based on both linear and non-linear support vector regression (SVR) models making use of a sequential forward floating selection of descriptors. The SVR model with only 6 serum proteins and zeta potential had higher accuracy (R(2) = 0.895) relative to the linear model (R(2) = 0.850) with 11 PCFs. Considering the initial pool of 148 descriptors, the APOB, A1AT, ANT3, and PLMN serum proteins along with NP zeta potential were identified as most significant to correlating NP-cell association. The present study suggests that QSARs exploration of NP-cell association data, considering the role of both NP protein corona and physicochemical properties, can support the planning and interpretation of toxicity studies and guide the design of NPs for biomedical applications.

The facile and efficient one-step synthesis and the full characterization of novel π-electron rich macrocycles, calix-[n]tetrolarenes (n = 4, 5), are described. The tetramer and the much rarer sized pentamer were easily prepared by reaction of the commercially available, partially methylated 1,2,3,5-benzenetetrol with paraformaldehyde under TFA catalysis, with a total isolated yield of 73%. The reaction is solvent sensitive, and the number of methylated oxygens also affects the tetramer/pentamer distribution. The compounds formed may be considered as “chimeric” macrocycles of calixarene and pyrogallol[n]arene that may serve as new building blocks in host–guest and supramolecular chemistry.

Forward osmosis (FO) desalination was investigated via 2-D numerical model of the fully coupled hydrodynamics and mass transfer equations. The model was formulated for a detailed composite channel structure (feed and draw channels, membrane skin layer and porous support) being capable of describing co-current or counter current cross operation where the membrane skin faces the salt feed solution (SFF) or where the membrane skin faces the draw solution (SFD). Simulations based on existing experimental FO data confirmed that FO operation in a counter-current/SFD mode provides slight improvement with respect to water flux, and reduced cross migration of feed and draw solutes relative to the co-current mode of operation. Analysis of existing FO data also revealed the dependence of the intrinsic membrane water permeability and solute transport coefficients on draw solute concentration. Simulation results indicated significant cross membrane migration of feed and draw solutes for long (~1 m) relative to short (~10 cm) FO channels. Moreover, up to an order of magnitude decline of draw solute concentration difference (along the membrane) can be encountered at the draw channel exit region. Simulation results suggest that accurate assessment of FO performance in long channels is critical for full-scale plant design in order to minimize salt leakage, optimize recovery, and setting accurate inlet/outlet conditions to enable simulations of membrane elements in series.

Nanoparticles (NPs) have great potential to increase the diagnostic capacity of many imaging modalities. MRI is currently regarded as the method of choice for the imaging of deep tissues, and metal ions, such as calcium ions (Ca(2+)), are essential ingredients for life. Despite the tremendous importance of Ca(2+) for the well-being of living systems, the noninvasive determination of the changes in Ca(2+) levels in general, and extracellular Ca(2+) levels in particular, in deep tissues remains a challenge. Here, we describe the preparation and contrast mechanism of a flexible easy to prepare and selective superparamagnetic iron oxide (SPIO) NPs for the noninvasive determination of changes in extracellular Ca(2+) levels using conventional MRI. We show that SPIO NPs coated with monodisperse and purified alginate, having a specific molecular weight, provide a tool to selectively determine Ca(2+) concentrations in the range of 250 µm to 2.5 mm, even in the presence of competitive ions. The alginate-coated magnetic NPs (MNPs) aggregate in the presence of Ca(2+) , which, in turn, affects the T2 relaxation of the water protons in their vicinity. The new alginate-coated SPIO NP formulations, which have no effect on cell viability for 24 h, allow the detection of Ca(2+) levels secreted from ischemic cell cultures and the qualitative examination of the change in extracellular Ca(2+) levels in vivo. These results demonstrate that alginate-coated MNPs can be used, at least qualitatively, as a platform for the noninvasive MRI determination of extracellular Ca(2+) levels in myriad in vitro and in vivo biomedical applications.

An experimental investigation was carried out to assess the removal efficiency of metal oxide nanoparticles from aqueous suspensions via sedimentation and the added benefit of membrane filtration. The study was conducted with aqueous suspensions of TiO2, ZnO, and CeO2 nanoparticles (NPs) of primary size of 10 nm–21 nm. The removal of NPs by gravitational settling was carried out with suspensions that were pretreated via pH adjustment and coagulant addition in order to increase the agglomerate size. Removal efficiencies were as high as 72.3–98.6% for the studied NPs with subsequent ultrafiltration of the remaining suspensions (post sedimentation) enabling essentially complete NP removal.

Relationships among fourteen different biological responses (including ten signaling pathway activities and four cytotoxicity effects) of murine macrophage (RAW264.7) and bronchial epithelial (BEAS-2B) cells exposed to six metal and metal oxide nanoparticles (NPs) were analyzed using both statistical and data mining approaches. Both the pathway activities and cytotoxicity effects were assessed using high-throughput screening (HTS) over an exposure period of up to 24 h and concentration range of 0.39-200 mg L(-1). HTS data were processed by outlier removal, normalization, and hit-identification (for significantly regulated cellular responses) to arrive at reliable multiparametric bioactivity profiles for the NPs. Association rule mining was then applied to the bioactivity profiles followed by a pruning process to remove redundant rules. The non-redundant association rules indicated that "significant regulation" of one or more cellular responses implies regulation of other (associated) cellular response types. Pairwise correlation analysis (via Pearson's χ(2) test) and self-organizing map clustering of the different cellular response types indicated consistency with the identified non-redundant association rules. Furthermore, in order to explore the potential use of association rules as a tool for data-driven hypothesis generation, specific pathway activity experiments were carried out for ZnO NPs. The experimental results confirmed the association rule identified for the p53 pathway and mitochondrial superoxide levels (via MitoSox reagent) and further revealed that blocking of the transcriptional activity of p53 lowered the MitoSox signal. The present approach of using association rule mining for data-driven hypothesis generation has important implications for streamlining multi-parameter HTS assays, improving the understanding of NP toxicity mechanisms, and selection of endpoints for the development of nanomaterial structure-activity relationships.

The biofouling propensity and cleaning effectiveness were evaluated for a new generation of polyamide thin-film composite (PA-TFC) membranes that are surface nano-structured (SNS) with terminally anchored hydrophilic polymer chains. The SNS-PA-TFC membranes were formed via surface graft polymerization onto the surface of polyamide base membranes previously activated via surface treatment with atmospheric pressure plasma. Poly(methacrylic acid) (PMMA) and polyacrylamide (PAAm) SNS-PA-TFC membranes were synthesized and evaluated with respect to their biofouling resistance using secondary wastewater from a municipal wastewater treatment (MWT) plant. Biofouling resistance and cleaning effectiveness were quantified via flux decline measurements in addition to imaging of the biofouled membranes before and after DI water and chemical (Na 2 ·EDTA) cleaning. Increased biofouling resistance was highest for the PMAA-SNS-PA-TFC membrane being a factor of 4.2 greater than for the commercial membrane of about the same salt rejection used in the MWT plant. Moreover, permeability recovery for the PMAA-SNS-PA-TFC membrane was higher by factors of up to ~1.2 relative to the reference commercial membrane upon cleaning with DI water and more aggressive chemical cleaning at high pressure. The present evaluation of the SNS-PA-TFC membranes suggests that biofouling resistance and cleaning effectiveness of RO membranes can be enhanced via hydrophilic brush layers.

q-Space diffusion MRI (QSI) was used to study the spinal cords of Long Evans shaker (les) rats, a model of dysmyelination, and their age-matched controls at different maturation stages. Diffusion was measured parallel and perpendicular to the fibers of the spinal cords of the two groups and at different diffusion times. The results showed that QSI is able to detect the dysmyelination process that occurs in this model in the different stages of the disease. The differences in the diffusion characteristics of the spinal cords of the two groups were found to be larger when the diffusion time was increased from 22 to 100 ms. We found that the radial mean displacement is a much better parameter than the QSI fractional anisotropy (FA) to document the differences between the two groups. We observed that the degree of myelination affects the diffusion characteristics of the tissues, but has a smaller effect on FA. All of the extracted diffusion parameters that are affected by the degree of myelination are affected in a diffusion time-dependent fashion, suggesting that the terms apparent anisotropy, apparent fractional anisotropy and even apparent root-mean-square displacement (rmsD) are more appropriate.

Diffusion NMR is a powerful tool for gleaning microstructural information on opaque systems. In this work, the signal decay in single-pulsed-field gradient diffusion NMR experiments performed on a series of phantoms of increasing complexity, where the ground truth is known a priori, was modeled and used to identify microstructural features of these complex phantoms. We were able to demonstrate that, without assuming the number of components or compartments, the modeling can identify the number of restricted components, detect their sizes with an accuracy of a fraction of a micrometer, determine their relative populations, and identify and characterize free diffusion when present in addition to the components exhibiting restricted diffusion. After the accuracy of the modeling had been demonstrated, this same approach was used to study fixed nerves under different experimental conditions. It seems that this approach is able to characterize both the averaged axon diameter and the relative population of the different diffusing components in the neuronal tissues examined.

The feasibility of utilizing chemically-enhanced seeded precipitation (CESP) for primary reverse osmosis (PRO) concentrate demineralization was evaluated, via both experimental field tests and process analysis, to assess its potential use in enabling recovery enhancement via secondary RO (SRO) desalting. Field evaluations of batch CESP along with process simulations for desalting of agricultural drainage (AD) water (6700–14,400 mg/L TDS, SIg = ~ 0.9) have suggested that a PRO-CESP-SRO desalting approach is both technically and economically feasible to enable overall desalting recovery of about 83% and, with partial concentrate recycling, of up to 93%. In the CESP process, initial partial lime treatment provides adsorptive removal of residual antiscalant from the PRO concentrate. This enables subsequent concentrate desupersaturation (with respect to the major scaling salt calcium sulfate) to occur via seeded gypsum precipitation, unimpeded by residual antiscalant. The desupersaturated PRO concentrate (~ 34% reduction in SIg from ~ 1.7 to ~ 1.1) can then be further desalted in an SRO step up to the limit that is feasible with antiscalant dosing for scale control. When considering the cost of residual brine disposal, the cost of AD water desalination by PRO-CESP-SRO on the basis of desalted water volume is lower than RO by up to 39%.

Biofilm formation, which frequently occurs in microbial infections and often reduces the efficacy of antibiotics, also perturbs many industrial and domestic processes. We found that a new class of water soluble pillar[5]arenes bearing phosphonium moieties (1, 2) and their respective ammonium analogues (3, 4) inhibit biofilm formation with IC50 values in the range of 0.67–1.66 μM. These compounds have no antimicrobial activity, do not damage red blood cell membranes, and do not affect mammalian cell viability in culture. Comparison of the antibiofilm activities of the phosphonium-decorated pillar[5]arene derivatives 1 and 2 with their respective ammonium counterparts 3 and 4 and their monomers 5 and 6, demonstrate that while positive charges, charge cooperativity and the pillararene platform are essential for the observed antibiofilm activity the nature of the charges is not.

It is estimated that up to 80% of bacterial infections are accompanied by biofilm formation. Since bacteria in biofilms are less susceptible to antibiotics than are bacteria in the planktonic state, biofilm-associated infections pose a major health threat, and there is a pressing need for antibiofilm agents. Here we report that water-soluble cationic pillararenes differing in the quaternary ammonium groups efficiently inhibited the formation of biofilms by clinically important Gram-positive pathogens. Biofilm inhibition did not result from antimicrobial activity; thus, the compounds should not inhibit growth of natural bacterial flora. Moreover, none of the cationic pillararenes caused detectable membrane damage to red blood cells or toxicity to human cells in culture. The results indicate that cationic pillararenes have potential for use in medical applications in which biofilm formation is a problem.

Resorcin[4]arenes (6) and pyrogallol[4]arenes (7) are concave molecules which were found to form large hexameric capsules in the solid state and in solution in the presence of specific guests. There after diffusion NMR have shown that 6, 7 and even octahydroxypyridine[4]arenes (8) form, spontaneously, hexameric capsules in organic solvents thus demonstrating that hexameric capsules are much more abundant than previously thought. In the following chapter after a brief introduction we describe the supramolecular structures of the hexamers of 6, 7 and 8. Then self-sorting and the guests affinity in the hexameric capsules of 6 and 7 are described after which the peculiar NMR spectra of encapsulated solvent molecules in the hexamers of 7 are describe in details. One of the main characteristics of molecular capsule it the ability of such system to isolate the guest from the bulk. Such systems can be regarded as nano-reactors where new chemistry and catalysis can emerge. Here we describe the recent example in which the hexameric capsules of 6 were used as nano-reactors and catalytic vessels. We end our essay by a short description of the recent developments in the field of metal organic nano-capsules (MONCs).

The influence of a pre-existing biofilm on RO membrane mineral scaling was evaluated using gypsum as a model scalant. The biofilm was established using microfiltered secondary treated wastewater effluent on-site in a wastewater treatment facility. Mineral scaling was then monitored via direct visual observation of crystal growth on the membrane surface in a transparent plate-and-frame RO cell. SEM imaging of the membrane surface and sectioned biofilm revealed gypsum crystals within the biofilm matrix, including the protrusion of crystal rods from within the biofilm. Both mineral scale surface coverage and crystal number density were greater in the presence of the biofilm. Moreover, individual mineral crystal growth rate within the biofilm was significantly higher relative to growth in the absence of a biofilm. Analyses of crystal growth and nucleation rates, within the biofilm and in its absence, suggest concentration polarization enhancement within the biofilm. The present study suggests that mineral scaling may not be restricted to tail elements in RO plants, but could also occur in lead elements where biofilms can enhance concentration polarization. Therefore, understanding of the coupling of biofouling and mineral scaling may be of particular significance to the operation and design of RO plants in water reuse applications.

An experimental study was carried out to demonstrate and quantify the feasibility of antiscalant (AS) removal from brackish water RO concentrate of high gypsum scaling propensity via lime treatment prior to seeded gypsum precipitation. Based on studies with model solutions, it was shown that sufficient AS removal (up to ∼90%) from RO concentrate is feasible via a lime treatment step (at a dose significantly lower than that required for conventional lime softening) to enable effective subsequent seeded gypsum precipitation. This two-step chemically-enhanced seeded precipitation (CESP) treatment of primary RO concentrate is suitable as an intermediate concentrate demineralization (ICD) stage for high recovery desalting employing secondary RO desalination. Analysis of gypsum precipitation and lime treatment kinetic data suggests that, after adequate CaCO 3 precipitation has been induced for effective AS scavenging, CaSO 4 desupersaturation can be achieved via seeded gypsum precipitation without retardation due to seed poisoning by AS. Also, the lime dose required to prevent seed poisoning during subsequent gypsum desupersaturation via seeded gypsum precipitation can be adequately assessed with a precipitation kinetics model that considers AS seed poisoning based on a Langmuir adsorption isotherm. The degree of AS removal after lime treatment increased linearly with the logarithm of the single lime dose additions. Staged lime dosing (i.e., multiple lime additions), however, removed a higher degree of AS relative to an equivalent single lime dose addition since a higher driving force for CaCO 3 precipitation could be maintained over the course of the lime treatment period.

The feasibility of removing calcium scale precursor ions from reverse osmosis (RO) concentrate by accelerated seeded precipitation (ASP) was investigated with the goal of increasing product water recovery and minimizing the volume of concentrate disposal from inland municipal wastewater desalination plants. Three seed materials were tested in laboratory trials — calcium carbonate, calcium sulfate and calcium phosphate. Calcium carbonate and calcium sulfate seed were not effective. The addition of calcium phosphate seed particles at 20 g L− 1 or phosphate ion in stoichiometric excess of the calcium concentration (250 mg L− 1 Ca = 6.25 mM Ca2+, 650 mg L− 1 HPO42− = 6.7 mM) decreased the calcium content in the RO concentrate to 10 mg L− 1. Evaluation of the accelerated seeded precipitation process using in-situ generated calcium phosphate seed at the pilot scale was performed on a 25 kL day− 1 pilot plant consisting of dissolved air flotation, ultrafiltration and reverse osmosis. The treated concentrate was filtered by a ceramic filtration system. Preliminary cost analyses indicate that high recovery RO using calcium phosphate precipitation can only be justified in inland situations where restrictions on concentrate disposal drive smaller evaporation pond storage volumes to offset the higher chemical and energy running costs.

Organophosphates are highly toxic substances, which cause severe brain damage. The hallmark of the brain injury is major convulsions. The goal of this study was to assess the spatial and temporal MR changes in the brain of paraoxon intoxicated rats. T2-weighted MRI and ¹H-MR-spectroscopy were conducted before intoxication, 3 h, 24 h, and 8 days postintoxication. T2 prolongation mainly in the thalami and cortex was evident as early as 3 h after intoxication (4-6% increase in T2 values, P 20% decrease, P 15%, P < 0.05). Animals who succumbed had extensive cortical edema, significant higher lactate levels and a significant decrease in NAA/creatine and NAA/choline levels compared to animals which survived the experiment. Organophosphates-induced brain damage is obvious on MR data already 3 h postintoxication. In vivo spectroscopic changes are more sensitive for assessing long-term injury than T2-weighted MR imaging. Early spectroscopic findings might be used as biomarkers for the severity of the intoxication and might predict early survival.