Transport of Cryptosporidium oocysts in porous media: role of straining and physicochemical filtration

The transport and filtration behavior of Cryptosporidium parvum oocysts in columns packed with quartz sand was systematically examined under repulsive electrostatic conditions. An increase in solution ionic strength resulted in greater oocyst deposition rates despite theoretical predictions of a significant electrostatic energy barrier to deposition. Relatively high deposition rates obtained with both oocysts and polystyrene latex particles of comparable size at low ionic strength (1 mM) suggest that a physical mechanism may play a key role in oocyst removal. Supporting experiments conducted with latex particles of varying sizes, under very low ionic strength conditions where physicochemical filtration is negligible, clearly indicated that physical straining is an important capture mechanism. The results of this study indicate that irregularity of sand grain shape (verified by SEM imaging) contributes considerably to the straining potential of the porous medium. Hence, both straining and physicochemical filtration are expected to control the removal of C. parvum oocysts in settings typical of riverbank filtration, soil infiltration, and slow sand filtration. Because classic colloid filtration theory does not account for removal by straining, these observations have important implications with respect to predictions of oocyst transport.     

The Discovery of Phenylbenzamide Derivatives as Grb7‐Based Antitumor Agents

Grb7 is a non‐catalytic protein, the overexpression of which has been associated with the proliferative and migratory potentials of cancer cells. Virtual screening strategies involving a shape‐based similarity search, molecular docking, and 2D‐similarity searches complemented by experimental binding studies (Thermofluor and isothermal titration calorimetry) resulted in the identification of nine novel phenylbenzamide‐based antagonists of the Grb7 SH2 domain. Moderate binding affinities were observed, ranging from K_d=32.3 μM for lead phenylbenzamide NSC 104999 ( 1 ) to K_d=1.1 μM for a structurally related compound, NSC 57148 ( 2 ). Deconvolution of the affinity data into its components revealed differences in lead binding, from being entropy based (lead 1 ) to enthalpically driven (NSC 100874 ( 3 ), NSC 55158 ( 4 ), and compound 2 ). Finally, the lead compound 1 was found to decrease the growth of MDA‐MB‐468 breast cancer cells, with an IC₅₀ value of 39.9 μM . It is expected that these structures will serve as novel leads in the development of Grb7‐based anticancer therapeutics.     

The role of endocrine disrupters in water recycling: risk or mania?

The widespread occurrence of endocrine disrupting chemicals (EDCs), such as steroid hormones, in secondary wastewater effluents has become a major concern in the water recycling practice. This paper investigates the risk of steroid hormone breakthrough during nanofiltration membrane filtration in water recycling applications. The results indicate a dynamic equilibrium between adsorption and desorption of steroid hormone with regard to the membrane. This equilibrium can be pH dependent and there is a possibility for release of steroid hormones at high pH during membrane cleaning procedures or erratic pH variations. Increase in water recovery can severely increase the hormone breakthrough concentration. The results also indicate a possibility of accumulation of steroid hormones in the NF membrane, followed by subsequent release.     

Engineering Carbon Nanotube Forest Superstructure for Robust Thermal Desalination Membranes

Desalination by membrane distillation (MD) using low‐grade or waste heat provides a potential route for sustainable water supply. Nonwetting, porous membranes that provide a selective pathway for water vapor over nonvolatile salt are at the core of MD desalination. Conventional water‐repelling MD membranes (i.e., hydrophobic and superhydrophobic membranes) fail to ensure long‐term desalination performance due to pore wetting and surface fouling. To address these challenges, a defect‐free carbon nanotube forest (CNTF) is engineered in situ on a porous electrospun silica fiber substrate. The engineered CNTF forms an ultrarough and porous interface structure, allowing outstanding wetting resistance against water in air and oil underwater. As a result of this antiwetting property, the composite CNTF membrane displays a stable water vapor flux and a near complete salt rejection (>99.9%) in the desalination of highly saline water containing low surface tension contaminants. The antimicrobial property of the composite CNTF membrane imparted by the unique forest‐like architecture and the oxidative effect of carbon nanotubes (CNTs) are further demonstrated. The results exemplify an effective strategy for engineering CNT architecture to elucidate the structure–property–performance relationship of the nanocomposite membranes and to guide the design of robust thermal desalination membranes.     

Salt cleaning of organic-fouled reverse osmosis membranes

Cleaning of organic-fouled reverse osmosis membranes with concentrated salt solutions has been investigated. Polysaccharides (alginate and pectin) and Suwannee River natural organic matter were used as model organic foulants. By systematically varying the chemical and physical factors affecting salt cleaning efficiency, we were able to elucidate the processes and mechanisms involved during salt cleaning. Chemical factors investigated included salt dose, salt type, and organic foulant composition, while physical factors included cleaning contact time, crossflow velocity, cleaning solution temperature, and permeation rate. Atomic force microscopy (AFM) was utilized to quantify the reduction in intermolecular foulant-foulant adhesion upon salt cleaning. Our results showed that salt cleaning was quite effective in cleaning reverse osmosis membranes fouled by gel-forming hydrophilic organic foulants, such as alginate and pectin. The proposed mechanism for salt cleaning involves structural changes of the cross-linked gel layer on the membrane surface upon exposure to the salt solution followed by an ion exchange reaction that induces the breakup of calcium-foulant bonds as well as calcium bridging (cross-linking) between foulant molecules. The results obtained from AFM force measurements as well as foulant release experiments confirmed that these chemical reactions were the major mechanisms of salt cleaning. Salt cleaning appears to be an effective cleaning method, and may prove useful for membrane-based advanced wastewater reclamation, where a large fraction of the organic foulants is hydrophilic.     

Family planning practices and attitudes among former Soviet new immigrant women in Israel

One hundred young new immigrant women from the former U.S.S.R. now living in Israel answered a detailed semi-open questionnaire regarding their knowledge, attitudes and behaviors in fertility and birth control issues. A collective family planning profile of these women is largely in line with that of the urban population of Slavonic U.S.S.R., combining early marriage, early and low fertility, the latter achieved by both abortion and contraception. Most respondents and their partners tried to prevent unwanted pregnancies, usually starting from traditional methods and switching over time to modern ones. An IUD remained most popular contraceptive among parous women, while use of the pill, very rare in the U.S.S.R., has almost doubled upon migration, mostly among younger women. Still, they kept some misleading ideas on the pros and cons of traditional versus modern methods, suggesting lack of adequate information also upon migration. Like their ex-compatriots, our women preferred to solve their birth control problems without external professional involvement. Contrary to the expected, free abortion ideology was not universally advocated by our respondents, and most were fully aware of abortion limitations in Israel. While rationally condemning abortion in both moral and health terms, most respondents still use it, this gap between beliefs and practice being indicative of their readiness to adopt efficient contraception. This switch occurs faster in women actively involved with host society via work or studies. Younger women were found to be more flexible and advanced in their family planning practices than were older ones, while almost no differences were related to education and origin within the U.S.S.R. This exploratory study suggests that any investment into promotion of healthy fertility control practices among new immigrants will be cost-effective in the near future.