BIMETALLIC NANOPARTICLES INTEGRATED MEMBRANES FOR GROUNDWATER REMEDIATION: SYNTHESIS, CHARACTERIZATION AND APPLICATIONS

The detoxification of chlorinated organics from groundwater, such as trichloroethylene (TCE), tetrachloroethylene (PCE), polychlorinated biphenyl (PCB) and carbon tetrachloride (CTC), is a challenging area. Reductive dechlorination has been investigated using iron and iron-based nanoparticles, such as bare Fe, sulfidized Fe (S-Fe) and palladized Fe (Pd-Fe). However, issues including particle agglomeration, difficulties in recycling and particle leaching have been reported to hinder the application and wide usage of these techniques. The integration of nanoparticles and membranes can address these issues because of the large surface area, stability, and the potential for versatile functionalities. In this study, commercial polyvinylidene difluoride (PVDF) microfiltration membranes were functionalized with poly (acrylic acid) (PAA) or poly (methacrylic acid) (PMAA). The functionalization allows the in-situ generation of iron-based nanoparticles through ion-exchange and reduction processes. These membranes were then tested for the removal of chlorinated organics from synthetic and site groundwater. Both the PAA and PMAA functionalization showed a responsive behavior in water flux through membranes. The deprotonation of carboxyl groups (-COOH → -COO-) makes PAA or PMAA become hydrophilic when pH \u3e pKa. Membrane permeability was decreased by 5-30 folds when pH increases from 2.3 to 10.5. PAA and PMAA are anionic polymers in the water at neutral and basic pH, which can capture metal cations for the in-situ synthesis of metallic nanoparticles through a reduction reaction. Uniform Pd-Fe particles with a size of 17.1 ± 4.9 nm were quantified throughout the pores of membranes using a developed focused ion beam cross-sectioning method. The reactive particles incorporated membranes presented over 96% degradation of 3,3\u27,4,4\u27,5-pentachlorobiphenyl (PCB-126) in less than 15 s residence time in passing through the membrane domains. Roles of Pd fractions, particle compositions and water parameters (pH and temperature) in degradation were evaluated using 2-chlorobiphenyl (PCB-1) as a model compound. The H2 evolution (Fe corrosion in water) was quantified with various Pd coverages on the Fe surface. H2 can be activated by catalytic Pd for the hydrodechlorination reaction. However, insufficient H2 production was observed under the higher Pd coverage (\u3e10.4%, corresponding to 5.5 wt%), resulting in the hindrance of dechlorination. Pd fractions from 0.5 wt% to 5.5 wt% (1.0% to 10.4% Pd coverage) yielded higher dechlorination performance. In addition, Pd-Fe bimetallic nanoparticles showed an18-fold mass normalized reaction rate (kmass) than that of isolated Pd and Fe nanoparticles. The investigation of nanoparticles’ intrinsic properties and PCB degradation guided the application of the Pd-Fe nanoparticles incorporated membranes in the treatment of contaminated groundwater. Cooperating with Arcadis Us Inc. (a global environmental consulting firm), the contaminant groundwater was obtained from a hazardous waste site in Louisville, KY. In a single pass of Pd-Fe-PMAA-PVDF membranes (0.5 wt% Pd), chlorinated organics in groundwater sample, such as TCE (177 ppb) and CTC(35 ppb), were degraded to 16 and 0.3 ppb, respectively, at 2.2 seconds of residence time. The surface area normalized reaction rate (ksa) in the treatment of the groundwater followed the order of CTC (0.101 Lm-2min-1)\u3e TCE (0.034 Lm-2min-1)\u3e PCE (0.017 Lm-2min-1)\u3e chloroform (0.002 Lm-2min-1). A long-term study showed less than 5% CTC and 20% PCE remained in a continuous flow through the membranes within the first 5 h (equivalent of 42 L/m2 treatment of water). A significant decrease in degradation performance was found after 36 h continuous flow (equivalent of 299 L/m2 treatment of water), which the reactivity of incorporated nanoparticles was recovered through regeneration using NaBH4. As expected, the on-site technology evaluation also showed effective remediation of the groundwater samples at the similar residence time of the degradation tests in the lab: less than 0.1% CTC, 12% TCE and 18% TCE remained at a residence time of 2.4 seconds. Successful regeneration and reuse of the reactive membranes were also achieved on-site. Analysis of typical samples was also validated by an environmental testing lab (Eurofins TestAmerica, Inc). The on-site remediation evaluation and the studies of regeneration/reuse enhance the optimization of the reactive membrane systems for the potential to scale up. Alternatives of Pd-Fe were studied in the solution phase to understand the fundamentals. S-Fe were prepared, after the synthesis of precursor Fe0 nanoparticles (spherical, ~35 nm radius), for the long-term study of CTC. Pd-Fe (0.3 mol% Pd) increased the degradation rate by 20-fold (ksa = 0.580 Lm-2min-1) compared to that of Fe while S-Fe presented a greater lifetime (deactivated after 17 days of aging). During the aging process, Fe core was converted to FeOOH and Fe3O4/γ-Fe2O3 which deactivated the particles. The restoration of Fe0 was achieved using NaBH4 (400 mol%), which regenerated Fe and Pd-Fe nanoparticles. Even though the Fe core was also restored for S-Fe, the formed FeSx layers (FeS, FeS2) disappeared. The results suggest that S-Fe extends the longevity of Fe, but the loss of FeSx makes S-Fe eventually perform like Fe in terms of CTC degradation

Pore Functionalized PVDF Membranes with In-Situ Synthesized Metal Nanoparticles: Material Characterization, and Toxic Organic Degradation

Functionalized PVDF membrane platforms were developed for environmentally benign in-situ nanostructured Fe/Pd synthesis and remediation of chlorinated organic compounds. To prevent leaching and aggregation, nanoparticle catalysts were integrated into membrane domains functionalized with poly (acrylic acid). Nanoparticles of 16–19 nm were observed inside the membrane pores by using focused ion beam (FIB). This technique prevents mechanical deformation of the membrane, compared to the normal SEM preparation methods, thus providing a clean, smooth surface for nanoparticles characterization. This allowed quantification of nanoparticle properties (size and distribution) versus depth underneath the membrane surface (0–20 μm). The results showed that nanoparticles were uniformly sized and evenly distributed inside the membrane pores. However, the size of nanoparticles inside the membrane pores was 13.9% smaller than those nanoparticles located on the membrane surface. Investigating nanoparticles inside membrane pores increases the accuracy of kinetic analysis and modeling aspects. Furthermore, the Fe/Pd immobilized membranes showed excellent performance in the degradation of chlorinated organics: Over 96% degradation of 3,3\u27,4,4\u27,5-pentachlorobiphenyl (PCB 126) was achieved in less than 15 s residence time in convective flow mode. The regeneration and reuse of this catalytic membrane system were also studied. Particles were examined in XRD upon formation, after deliberate oxidation, and after regeneration. The regenerated sample showed the same crystalline pattern as the original sample. Repeated degradation experiments demonstrated successful PCB 126 dechlorination with nanoparticles regenerated for four cycles with only a small loss in reactivity. It demonstrated that Fe/Pd immobilized membranes have the potential for large-scale remediation applications

High-efficiency segmented thermoelectric power generation modules constructed from all skutterudites

Development of thermoelectric conversion technology for power generation can alleviate the demand for fossil energy and increase the efficiency of energy utilization. To achieve more efficient heat-to-electric conversion, it is desirable to maximize the figure of merit (zT) over a wide temperature range. Constructing a segmented thermoelectric device by serially connecting materials with high zT at different operating temperatures has been proven feasible. However, the issue of compatibility of different thermoelectric materials and the method of connecting different segments to ensure high interfacial stability remain unsolved. Herein, we demonstrate a full skutterudite-based segmented thermoelectric power generation module. The use of thermoelectric materials from the same parent avoids the difference in thermal expansion coefficients and compatibility factors and allows the preparation of thermoelectric junctions by a one-step sintering process. As a result, a high module efficiency of 10.4% is obtained owing to the rational design of the materials, device geometry, and interfaces and is the highest value among skutterudite-based modules reported so far

Automatic Lateralization of Temporal Lobe Epilepsy Based on MEG Network Features Using Support Vector Machines

Correct lateralization of temporal lobe epilepsy (TLE) is critical for improving surgical outcomes. As a relatively new noninvasive clinical recording system, magnetoencephalography (MEG) has rarely been applied for determining lateralization of unilateral TLE. Here we propose a framework for using resting-state brain-network features and support vector machine (SVM) for TLE lateralization based on MEG. We recruited 15 patients with left TLE, 15 patients with right TLE, and 15 age- and sex-matched healthy controls. The lateralization problem was then transferred into a series of binary classification problems, including left TLE versus healthy control, right TLE versus healthy control, and left TLE versus right TLE. Brain-network features were extracted for each participant using three network metrics (nodal degree, betweenness centrality, and nodal efficiency). A radial basis function kernel SVM (RBF-SVM) was employed as the classifier. The leave-one-subject-out cross-validation strategy was used to test the ability of this approach to overcome individual differences. The results revealed that the nodal degree performed best for left TLE versus healthy control and right TLE versus healthy control, with accuracy of 80.76% and 75.00%, respectively. Betweenness centrality performed best for left TLE versus right TLE with an accuracy of 88.10%. The proposed approach demonstrated that MEG is a good candidate for solving the lateralization problem in unilateral TLE using various brain-network features

Detection Methods and Clinical Applications of Circulating Tumor Cells in Breast Cancer

Circulating Tumor Cells (CTCs) are cancer cells that split away from the primary tumor and appear in the circulatory system as singular units or clusters, which was first reported by Dr. Thomas Ashworth in 1869. CTCs migrate and implantation occurs at a new site, in a process commonly known as tumor metastasis. In the case of breast cancer, the tumor cells often migrate into locations such as the lungs, brain, and bones, even during the early stages, and this is a notable characteristic of breast cancer. Survival rates have increased significantly over the past few decades because of progress made in radiology and tissue biopsy, making early detection and diagnosis of breast cancer possible. However, liquid biopsy, particularly that involving the collection of CTCs, is a non-invasive method to detect tumor cells in the circulatory system, which can be easily isolated from human plasma, serum, and other body fluids. Compared to traditional tissue biopsies, fluid sample collection has the advantages of being readily available and more acceptable to the patient. It can also detect tumor cells in blood earlier and in smaller numbers, possibly allowing for diagnosis prior to any tumor detection using imaging methods. Because of the scarcity of CTCs circulating in blood vessels (only a few CTCs among billions of erythrocytes and leukocytes), thorough but accurate detection methods are particularly important for further clinical applications

Reinventing ‘Many Voices’: MacBride and a Digital New World Information and Communication Order

The MacBride Commission Report was arguably one of the most significant multilateral interventions in the history of international communication. This article charts its emergence at the time of deeply contested Cold War politics, coinciding with the rise of the southern voices in the global arena, led by the non-aligned nations. Thirty-five years after the report's publication, has the global media evolved into a more democratic system, demonstrating greater diversity of views and viewpoints? Despite the still formidable power of US-led western media, the article suggests that the globalisation and digitisation of communication has contributed to a multi-layered and more complex global media scene, demonstrating the “rise of the rest”

Genomic Analyses Reveal Mutational Signatures and Frequently Altered Genes in Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers worldwide and the fourth most lethal cancer in China. However, although genomic studies have identified some mutations associated with ESCC, we know little of the mutational processes responsible. To identify genome-wide mutational signatures, we performed either whole-genome sequencing (WGS) or whole-exome sequencing (WES) on 104 ESCC individuals and combined our data with those of 88 previously reported samples. An APOBEC-mediated mutational signature in 47% of 192 tumors suggests that APOBEC-catalyzed deamination provides a source of DNA damage in ESCC. Moreover, PIK3CA hotspot mutations (c.1624G>A [p.Glu542Lys] and c.1633G>A [p.Glu545Lys]) were enriched in APOBEC-signature tumors, and no smoking-associated signature was observed in ESCC. In the samples analyzed by WGS, we identified focal (<100 kb) amplifications of CBX4 and CBX8. In our combined cohort, we identified frequent inactivating mutations in AJUBA, ZNF750, and PTCH1 and the chromatin-remodeling genes CREBBP and BAP1, in addition to known mutations. Functional analyses suggest roles for several genes (CBX4, CBX8, AJUBA, and ZNF750) in ESCC. Notably, high activity of hedgehog signaling and the PI3K pathway in approximately 60% of 104 ESCC tumors indicates that therapies targeting these pathways might be particularly promising strategies for ESCC. Collectively, our data provide comprehensive insights into the mutational signatures of ESCC and identify markers for early diagnosis and potential therapeutic targets

Chronic Cadmium Exposure Induces Impaired Olfactory Learning and Altered Brain Gene Expression in Honey Bees (<i>Apis mellifera</i>)

The honey bee (Apis mellifera) plays vital ecological roles in the pollination of crops and the maintenance of ecological balance, and adult honey bees may be exposed to exogenous chemicals including heavy metals during their foraging activities. Cadmium (Cd) is regarded as a nonessential toxic metal and is readily accumulated in plants; honey bees can therefore acquire Cd through the collection of contaminated nectar. In the present study, honey bees were chronically exposed to Cd to investigate the effects of sublethal cadmium doses on the olfactory learning and brain gene expression profiles of honey bees. The results showed that Cd-treated bees exhibited significantly impaired olfactory learning performances in comparison with control bees. Moreover, the head weight was significantly lower in Cd-treated bees than in control bees after chronic exposure to Cd. Gene expression profiles between the Cd treatment and the control revealed that 79 genes were significantly differentially expressed. Genes encoding chemoreceptors and olfactory proteins were downregulated, whereas genes involved in response to oxidative stress were upregulated in Cd-treated bees. The results suggest that Cd exposure exerts oxidative stress in the brain of honey bees, and the dysregulated expression of genes encoding chemoreceptors, olfactory proteins, and cytochrome P450 enzymes is probably associated with impaired olfactory learning in honey bees

Effect of Lipid Additives and Drug on the Rheological Properties of Molten Paraffin Wax, Degree of Surface Drug Coating, and Drug Release in Spray-Congealed Microparticles

Paraffin wax is potentially useful for producing spray-congealed drug-loaded microparticles with sustained-release and taste-masking properties. To date, there is little information about the effects of blending lipids with paraffin wax on the melt viscosity. In addition, drug particles may not be entirely coated by the paraffin wax matrix. In this study, drug-loaded paraffin wax microparticles were produced by spray-congealing, and the effects of lipid additives on the microparticle production were investigated. The influence of lipid additives (stearic acid, cetyl alcohol, or cetyl esters) and drug (paracetamol) on the rheological properties of paraffin wax were elucidated. Fourier transform-infrared spectroscopy was conducted to investigate the interactions between the blend constituents. Selected formulations were spray-congealed, and the microparticles produced were characterized for their size, drug content, degree of surface drug coating, and drug release. The viscosity of wax-lipid blends was found to be mostly lower than the weighted viscosity when interactions occurred between the blend constituents. Molten paraffin wax exhibited Newtonian flow, which was transformed to plastic flow by paracetamol and pseudoplastic flow by the lipid additive. The viscosity was decreased with lipid added. Compared to plain wax, wax-lipid blends produced smaller spray-congealed microparticles. Drug content remained high. Degree of surface drug coating and drug release were also higher. The lipid additives altered the rheological properties and hydrophobicity of the melt and are useful for modifying the microparticle properties