Large Void Volume Research Articles

BGzEro – backfilling measures with low CO2 footprint

Abstract. In Germany, the Federal Company for Radioactive Waste Disposal (BGE) is responsible for the construction and operation of deep, geological repositories. BGE operates the Asse II mine and the Konrad and Morsleben repositories. Initially, these mines were excavated to extract raw materials. As a result, they have large void volumes on multiple levels. The stability of the unfilled cavities is limited in time so that backfilling measures are required for stabilisation. However, there are many requirements to consider when selecting backfill materials. BGE aims at making its locations climate neutral. Backfilling measures are particularly affected by this effort because of the large material volumes required and the greenhouse gas emissions that are released during material transport and during the entire material production chain. Bulk materials that are produced from the rock debris from the excavation of the respective mine have the smallest carbon dioxide (CO2) footprint. In order to use this rock debris, this material will be stored in underground excavations and large voids. In order to backfill the underground cavities in accordance with the requirements, the debris will be crushed in an underground crushing plant prior to backfilling. However, numerous cavities in the three mines mentioned above can only be backfilled with flowable, self-levelling and self-hardening materials. Generally, cement-based backfill materials and magnesia binders can be distinguished. The CO2 footprint of mixtures with cement increases primarily with the proportion of Portland cement clinker. For this purpose, recipes containing high proportions of supplementary cementitious materials such as pozzolan and latent hydraulic additives have been developed. Magnesia binders contain the binders magnesium oxide and/or magnesium hydroxide. Depending on the raw materials and the manufacturing process, different amounts of greenhouse gases are generated during their production. The classic approach is to use magnesium oxide, which is obtained by calcining magnesite (MgCO3). However, a lot of energy is required for this process, and the carbon dioxide content of the magnesite is released. Due to the extensive experience in the development of backfill materials and emplacement technologies, BGE has entrusted BGE TECHNOLOGY GmbH with the optimisation of the procedures for backfilling and the development of new backfill materials with the lowest possible CO2 footprint. Thus, raw materials and supply chains have been evaluated and are improved with regard to their environmental performance, taking into account all aspects of transport and logistics. The current focus of work is on the development of magnesia binders with natural brucite (magnesium hydroxide). Another positive aspect is the reduction of heat development of the backfill material during hardening. Furthermore, the reliability of supply for the implementation of the backfilling measures can be increased by a market analysis. The examples show that BGE and BGE TECHNOLOGY GmbH are on the right track to protect humans and the environment through the safe disposal of radionuclides and the realisation of sustainable, future-oriented technologies.

Adsorption effect of porous zirconia for carbon dioxide under the influence of various factors

Global warming and environmental deterioration have caused socially catastrophic events, arousing people’s interest in discovering the root causes of such events. Looking for an economically efficient and highly adsorbing carbon dioxide adsorbent has become one of the research priorities. Porous zirconia is an ideal candidate material for absorbing CO2 due to its distinctive acid-base property and a large number of active sites. The present study analyzed the effects of external factors (e.g., porous zirconia, including temperature, pH value, and humidity) and internal factors (e.g., crystal structure, lattice defects, and percentage of active sites in zirconia) on the adsorption performance of porous zirconia. Porous zirconia was found to have a high adsorption efficiency at pH 3∼6 under humid conditions. When the crystal structure of zirconia was tetragonal, monoclinic, or tetrahedral, the zirconia had a larger void volume and a larger number of active vacancies and oxygen vacancies. Modifying and increasing oxygen vacancies resulted in a larger number of active sites and a greater Gibbs free energy in the ZrO2 materials and their composites.

A highly robust {ZnTb}n-Organic framework for excellent catalytic performance on cycloaddition reaction of epoxides with CO2

Effective chemical fixation of CO2 into high value-added industrial raw materials, recognized as an effective strategy to alleviate energy crisis and environmental pollution, makes the research of innovative catalysts a hot topic. Herein, a robust {ZnTb}n-chain-based framework of {[ZnTb(CPPDP)(H2O)]·5DMF·H2O}n (NUC-62) achieved from the solvothermal condition was reported. In NUC-62, nanoporous channels (aperture ca. 10.5 Å) are shaped by six rows of {ZnTb(CO2)5(H2O)}n chains, which is the first reported 3d-4f heterometallic chain with the staggered arrangement of Zn2+ and Tb3+. As for the activated NUC-62a with the removal of lattice and coordinated DMF and H2O, the host framework characterizes the merits of exposed Lewis-acidic metal sites, high specific surface, large void volume and stable chemical property. Furthermore, NUC-62a was tested as a heterogenous catalyst for the two organic reactions of cycloaddition of CO2 with epoxides and Knoevenagel condensation of aldehydes and malononitrile, in which NUC-62a display the high catalytic performance along with high selectivity and excellent recyclability. Hence, this work provides an effective synthesis strategy for MOFs-based catalysts.

Impact of double cryogelation process on a macroporous dye-affinity hydrogel.

Cryogels with interconnected channels allow high flow-through properties and mass transfer when dealing with complex mixtures such as non-clarified crude extracts. However, their mechanical strength can be challenged due to a large void volume inside the polymeric network. We have addressed this problem by forming a double-layer cryogel applied as a dye-affinity chromatography gel. In this study, poly(acrylamide-co-allyl glycidyl ether) cryogel was prepared at sub-zero temperature. The second layer was then prepared inside the primary cryogel under the same conditions to form a double-layer network. Cibacron Blue F3GA, a dye molecule, was immobilized on the surface of the cryogels. Bovine serum albumin was used as a model molecule to study the adsorption/elution procedure in batch and continuous modes. The maximum batch binding capacity and the dynamic binding capacity for the single-layer cryogel were 18 and 0.11, and for the double-layer cryogel were 7.5 and 0.9 mg/g of gel, respectively. However, the mechanical stability of the double-layer cryogel increased 7-fold (144 kPa). It was found that the kinetic and adsorption isotherms follow pseudo-second-order and Freundlich models, respectively. The regeneration of the columns after adsorption/elution cycles was evaluated, and no significant loss of capacity was observed after 10 cycles.

Multimodal 3D printing of biodegradable shape memory elastomer resins for patient specific soft tissue repair

Acrylated poly(glycerol-dodecanedioate) (APGD), a biodegradable shape memory polymer, is a photocurable resin developed for 3D printing of biomaterial implants that is especially suited for minimally invasive procedures. 3D printing has numerous advantages over traditional manufacturing modalities including production of complex porous geometries, improved feature resolution, and lower production costs on a per part basis for low volume clinical production. Material extrusion (ME) and vat photopolymerization (VP) printing are two prevalent 3D printing modalities used in tissue engineering. Compared to VP printing, ME printing offers a higher degree of customization by allowing co- or multi-material prints, along with biologic cell printing. VP printing offers higher throughput and capability for printing more complex geometries, versus ME printing, with shorter manufacturing times, making it a more commercially viable choice for clinically translatable materials. Motivated by each printing modalities’ unique advantages, APGD resins for ME and VP printing were developed and assessed for crosslinker and photoinitiator (PI) concentration effect on resin time to gel point, storage modulus and viscosity. Increasing crosslinker concentration decreased the gel time and increased the storage modulus of cured resin. Significant differences in printed sample geometry along with material and mechanical properties resulted from using the two printing modalities. ME samples had larger void volume (6.1 ± 1.2% vs. 0.2 ± 0.4%), lower gel content (55.3 ± 2.6% vs. 68.7 ± 1.9%), and less shape fixity (77.4 ± 4.7 vs. 97.3 ± 3.7%) compared to VP samples. VP printing generated complicated 3D anatomic shapes of higher quality than ME printing. In conclusion, this manuscript provides the first report of APGD 3D printing that can be applied to shape memory, resorbable medical devices.

Nanoporous {Y2}-Organic Frameworks for Excellent Catalytic Performance on the Cycloaddition Reaction of Epoxides with CO2 and Deacetalization-Knoevenagel Condensation.

Stable metal-organic frameworks containing periodically arranged nanosized pores and active Lewis acid-base active sites are considered as ideal candidates for efficient heterogeneous catalysis. Herein, the exquisite combination of [Y2(CO2)7(H2O)2] cluster (abbreviated as {Y2}) and multifunctional linker of 2,4,6-tri(2,4-dicarboxyphenyl)pyridine (H6TDP) led to a nanoporous framework of {[Y2(TDP)(H2O)2]·5H2O·4DMF}n (NUC-53, NUC = North University of China), which is a rarely reported binuclear three-dimensional (3D) framework with hierarchical tetragonal-microporous (0.78 nm) and octagonal-nanoporous (1.75 nm) channels. The inner walls of these channels are aligned by {Y2} clusters and plentifully coexisted Lewis acid-base sites of YIII ions and Npyridine atoms. Furthermore, NUC-53 has a quite large void volume of ∼65.2%, which is significantly higher than most documented 3D rare-earth-based MOFs. The performed catalytic experiments exhibited that activated NUC-53 showed a high catalytic activity on the cycloaddition reactions of CO2 with styrene oxide under mild conditions with excellent turnover number (TON: 1980) and turnover frequency (TOF: 495 h-1). Moreover, the deacetalization-Knoevenagel condensation reactions of benzaldehyde dimethyl acetal and malononitrile could be efficiently prompted by the heterogeneous catalyst of NUC-53. These findings not only pave the way for the construction of nanoporous MOF based on rare-earth clusters with a variety of catalytic activities but also provide some new insights into the catalytic mechanism.

Fungicidal amphotericin B sponges are assemblies of staggered asymmetric homodimers encasing large void volumes.

Amphotericin B (AmB) is a powerful but toxic fungicide that operates via enigmatic small molecule-small molecule interactions. This mechanism has challenged the frontiers of structural biology for half a century. We recently showed AmB primarily forms extramembranous aggregates that kill yeast by extracting ergosterol from membranes. Here, we report key structural features of these antifungal 'sponges' illuminated by high-resolution magic-angle spinning solid-state NMR, in concert with simulated annealing and molecular dynamics computations. The minimal unit of assembly is an asymmetric head-to-tail homodimer: one molecule adopts an all-trans C1-C13 motif, the other a C6-C7-gauche conformation. These homodimers are staggered in a clathrate-like lattice with large void volumes similar to the size of sterols. These results illuminate the atomistic interactions that underlie fungicidal assemblies of AmB and suggest this natural product may form biologically active clathrates that host sterol guests.

New perspectives on structural parameters and hydrophobic model inspired by a superhydrophobic Cu cone-flower coating

Superhydrophobic films have been successfully prepared on various substrates by finely controlling surface micro/nanostructure's roughness and reducing surface energy. However, there is no unified conclusion about the correlation of surface roughness and 3D volume parameters to wettability. Herein, we fabricated a superhydrophobic film composed of hierarchical Cu cone-flowers via facile one-step pulse electrodeposition with a 30% duty cycle for 20 min. Based on this film, the relationship between roughness/volume parameters and hydrophobicity was well studied. The resulting cone-flower film exhibits excellent corrosion resistance and self-cleaning properties due to a high water contact angle (WCA) of ~160° and a low sliding angle (SA) of ~3°. The large roughness skewness (Rsk = 0.7–1.3) and void volume ratio (Vvc/Vmc > 1.5) are shown to be more desirable to achieve superhydrophobic surfaces. Moreover, a new hydrophobic model is proposed to explain the above results, which means that the nanoscale air cushions share most of the gravity of water droplets to help microscale air cushions closer to the Cassie state. Further experiments by adding or destroying the nanostructures to observe the change of hydrophobicity well verified our conjecture.

Synthesis and energy applications of m ulti‐shell micro/n ano‐spheres

Nowadays, multishelled hollow materials having various compositions and structures have drawn huge attention of researchers. In comparison to the single-shelled hollow structures, which become advantageous and preferred due to their large void volume and high surface-to-volume ratio, it is considered that hollow materials with multi-shell structures can gain extra benefits from their specially constituted inner structures. This review article aims on the progress in the synthesis and energy applications of multishelled spherical nano-materials in last decade. The synthetic strategies include the hard templating, soft templating, sacrificial templating, and template-free technologies. The review further approaches toward the fundamentals of each of the synthetic strategies. Moreover, it addresses the challenges and the advantages of each of the synthetic strategies. This also emphasizes on the potential applications of the these specially structured micro- and nano-materials in the field of electrocatalysis, electrodes, lithium ion batteries, and solar cells. The correlation between the number of shells, geometric, and compositional structure with their properties and specific applications has also been addressed.

Effects of ZIF-8 MOFs on structure and function of blood components.

ZIF-8 MOFs, with their large specific surface area and void volume, unique biodegradability and pH sensitivity, and significant loading capacity, have been widely used as carrier materials for bioactive molecules such as drugs, vaccines and genes. In these applications, ZIF-8 MOFs are usually delivered intravenously. Therefore, it is necessary to know the interaction between ZIF-8 MOFs and blood components, which from this sense is a key factor affecting their delivery effectiveness and biosafety. However, until now there has been no report on the evaluation of hemocompatibility of ZIF-8 MOFs. The lack of biosafety information of ZIF-8 MOFs seriously impedes their clinical applications. In this work, we studied the biosafety of two different sizes of ZIF-8 MOFs, mainly focusing on their in vivo and in vitro effects on the key components of blood (red blood cells (RBCs), platelets, etc.) and the coagulation function. It was found that, in vitro, a high concentration of ZIF-8 MOFs could induce RBC aggregation and hemolysis, and prolong the coagulation time. In vivo, intravenous administration of 45 mg kg−1 ZIF-8 MOFs significantly disturbed the RBC and platelet-related blood routine indexes, as well as coagulation function indexes, but it did not cause significant abnormalities in blood coagulation and tissue structures (heart, liver, spleen, lung, and kidney).

Porous and Nonporous Coordination Polymers Induced by Pseudohalide Ions for Luminescence and Gas Sorption.

The three-dimensional (3D) coordination polymers [Cd(tpmd)(NCX)2]n [X = O (1), S (2), and BH3 (3); tpmd = N,N,N',N'-tetrakis(pyridin-4-yl)methanediamine] have been determined to display their network structures through coordinated anionic ligands. Polymers 1 and 2 show nonporous structures, whereas polymer 3 shows a porous coordination framework. On the basis of the Cd(II) network structures, the 3D coordination polymer [Zn(tpmd)(NCBH3)2]n·nMeOH (4) was self-assembled. In the cases of polymers 1 and 2, pseudohalide ions acted to form nonporous network structures; however, in polymers 3 and 4, NCBH3- helps to construct porous network structures. Polymers 1-4 show strong ultraviolet luminescence emissions, depending on the pseudohalide ions present, compared to the tpmd ligands. Interestingly, coordination polymers 3 and 4 that possess NCBH3- ions exhibit high porosities and gas sorption properties. The polymers appeared to absorb N2, H2, CO2, and CH4. In the case of polymer 4, the structure is almost identical with that of polymer 3, except for the Cd(II) ion. However, polymer 4 has a larger void volume and higher gas absorption ability for N2 gas than polymer 3. For the sorption of gases, polymers 3 and 4 showed similar behaviors.

Mesofluidic separation versus dead-end filtration

Here we compare dead-end filtration to mesofluidic separation, which produces filtrate depleted of particles larger than a desired cutoff size. Dead-end filtration is well-established across a broad range of industries but rapidly loses throughput with even modestly concentrated slurries due to significant depth and cake fouling. Periodic back pulsing reduces but does not eliminate fouling. In contrast, mesofluidic separation is an emerging technique that uses periodic arrays of posts (here 500 μm in diameter 800 μm apart) instead of membranes or porous media to achieve separation with continuous inlet and outlet flows. Large internal void volumes reduce or eliminate cake and depth fouling, permitting operation at significant flowrates. Mesofluidic separators are similar to microfluidic separators but operate at higher flowrates (e.g., ~1 L/min and higher versus ~10 mL/h) and have larger dimensions (e.g., millimeters versus microns). Yet, mesofluidic separation has not been compared directly to dead-end filtration. Here we compare and contrast these two approaches on two key performance metrics: pressure drop and flowrate over time. We find that mesofluidic separation maintains high throughput and low pressure drop orders of magnitude longer than dead-end filtration. Head-to-head comparison with “sticky” slurries finds mesofluidic separators lose <6% of flow in contrast to dead-end filters that lose >55% both over 7 h. Logarithmic projection supported by the data projects <20% loss of flow over three years under high bay conditions.

Enhancement of Low-Temperature NH3-SCR Catalytic Activity and H2O Resistance Ability Over MnOx/TiO2 Catalyst by Expanded Graphite

A combination of large void volume and rich microporous structure enables expanded graphite (EG) to possess excellent adsorption properties. Furthermore, it is discovered to be hydrophilic with the capability of adsorbing NOx. The ball milling method was applied in preparation of the MnOx/TiO2 modified by expanded graphite catalysts with the aim to improve SCR activity and resistance to H2O and SO2. An optimal SCR performance was obtained over the catalysts with 5 wt% EG doping. Subsequently, an investigation was conducted by XPS, NH3-TPD, H2-TPR into the understanding of the SCR catalytic performance of MnOx/TiO2 at low-temperature. As revealed by the investigation results, the catalyst modified by EG had more Mn4+ species and could absorb more oxygen, which allowed it to present more surface acid sites that could boost SCR activity. In addition, it was discovered that the introduction of EG could facilitate the improvement on the resistance to H2O and SO2. Expanded graphite (EG) has used to improve the SCR activity and resistance to H2O and SO2 over the MnOx/TiO2. The catalyst with the addition of 5% EG was found to have more surface acid sites, surface adsorbed oxygen and Mn4+ species.

Structured Fe3O4-doped ordered mesoporous carbon catalyst supported on sintered metal fibers for intensifying phenol degradation

Microfibrous-structured catalysts are materials that address the mass/heat transfer limitation and achieve catalytic process intensification, showing great promise for enabling practical environmental catalysis such as continuous wastewater treatment process. In this work, Fe3O4-doped ordered mesoporous carbon (OMC) catalyst supported on porous sintered metal fibers (Fe-OMC/SMFs) was prepared using a new yet simple “one-pot” method and used as a Fenton-like heterogeneous catalyst. The obtained catalysts were carefully characterized by TGA-DTG, BET, XRD, SEM-EDS, XPS and H2-TPR techniques. Structured reactor was designed and developed using developed microfibrous-structured catalysts, demonstrating an excellent catalytic performance for continuous heterogeneous Fenton oxidation of phenol. Specifically, both phenol and H2O2 conversions increased slightly as carbonization temperatures increasing from 400 to 1000°C. Compared to Fe-OMC pellet catalyst, the developed structured catalyst showed an improved catalytic activity (i.e. ∼100 % phenol/H2O2 conversions), and remarkable long-term stability (i.e. ∼100 % phenol conversion over a 7-h longevity test). Additionally, the developed Fe-OMC/SMFs catalyst showed Fe leaching amounts of ∼10mgL−1 during reaction, being significantly lower than that of Fe-OMC pellet catalyst (i.e. ∼500mgL−1). Experimental results revealed that well-dispersed Fe3O4 nanoparticles in OMC and three-dimensional microfibrous networks and large void volume of SMFs support are significantly benefit to enhance mass transfer and contacting efficiency between active sites and reactants, and thus achieve the process intensification of catalytic degradation of phenol.

Preparation and characterization of Cu and Mn modified beta zeolite membrane catalysts for toluene combustion

Cu and Mn as well as their mixed oxides modified beta zeolite membrane (Beta) coating on paper-like stainless steel fibers (PSSF) catalysts were successfully prepared and applied in toluene combustion. Firstly, Beta/PSSF with different crystallization temperature, crystallization time, Si/Al ratios etc. were prepared using secondary growth method, meanwhile, XRD, SEM and N2 adsorption-desorption isotherms were utilized to analyze the structures of the samples, respectively. Then, Cu and Mn as well as their mixed oxides loaded onto the obtained beta zeolite membrane with the optimal parameter were prepared by impregnating method. Finally, toluene combustion experiment was performed over a fixed-bed reactor. The experimental results depicted that continuous and well-intergrown beta zeolite membrane covered on the PSSF with typical truncated bipyramidal shape, and Beta/PSSF had a three-dimensional network with large void volume and majority of microporous. For the catalysts, the copper element existed as Cu2+ and Cu1+, and manganese element existed as Mn4+, Mn3+, and Mn2+. As a result, the catalytic activities for toluene combustion over mixed oxides as catalysts were superior to the single metal oxide catalysts. The T10, T50 and T90 of toluene combustion were dramatically decreased over Cu-Mn (1:3)- Beta/PSSF.

Fabrication of functional hollow magnetic polymeric nanoparticles with controllable magnetic location

Hollow magnetic polymeric particles (HoMPs) with controllable location of magnetic nanoparticles and functionality of polymeric double shell were fabricated by means of the facile soft templating method in one-pot. During the in situ miniemulsion polymerization, hexadecane, the Ostwald suppressing agent, acted as a soft template, which later formed a controllable void size. Adjusting ratio and polarity of monomers caused the difference in polymerization kinetics and phase separation, which resulted in HoMPs with two internal architectures, i.e., HoMPs-I with magnetic at the inner shell/void interface and HoMPs-II with magnetic-embedded shell. Both HoMPs-I and II contained high magnetic content (30–50%wt) with sufficient saturation magnetization (16–30 emu/g). With large void volume (>50%) and distinct shell polarity, either hydrophilic Rhodamine B or hydrophobic fluorescein isothiocyanate dye was selectively loaded. After functionalization with a cancer cell targeting ligand, folic acid (FA), the cellular uptake of HoMPs-FA in HeLa cell was improved with 100% cell viability and without cell destruction. This fabrication method provides a facile mean to tailor surface chemistry and architectures of hollow hybrid particles, which would be potentially used for efficient treatment of cancer tumors.

Experimental and numerical investigation of noise generation due to acoustic resonance in a cavitating valve

In order to study cavitation induced noise generation in a hydraulic system, cavitation is generated at a planar orifice. The sudden condensation (implosion) of vapor results in shock waves which excite the connected hydraulic pipes with pressure fluctuations. The synchronization between the continuous condensation and evaporation process and shock wave reflection can result in a stationary wave with superelevated pressure amplitudes. The fluid-borne sound is transferred through the mechanical structure into the air, where it can be perceived as a distracting whistling noise. A high-speed camera is used to visualize the void volume. Dynamic pressure signals are recorded in the vicinity of the orifice to analyze the pressure pulsation. The operating point is varied, the orifice geometry is changed and the reflection properties of the pipe on the up- and downstream sides are changed too. In addition, CFD (Computational Fluid Dynamics) simulations of the test bench are used to investigate the root cause of the whistling noise. With regards to representative operating points, the numerical results confirm the measured shedding vapor frequency, particularly the pressure pulsation frequency in the pipe and its amplitude. The conjunction of the experimental and numerical investigations provides the following findings: By reducing the discharge pressure, the void volume increases, which leads to a reduction of the resonance frequency of the pipe downstream of the orifice. For large void volumes, the pressure wave reflection at the void volume can be identified in the amplitude spectrum. The whistling noise depends on the history of the flow field. So, the increase and the reduction of the discharge pressure level leads to different whistling ranges. The whistling range decreases with the increasing length of the pipe resonator. Besides that, the order of the dominant resonance frequency increases. The experimental and numerical results indicate that the whistling noise only occurs, when the jet downstream of the orifice and hence the vapor is perpendicular to the sound propagation in the pipe resonator.

Pairing Asymmetric Gas Diffusion Media for High-Power Fuel Cell Operation

Proton exchange membrane fuel cell (PEMFC) power production is highly influenced by the properties of the gas diffusion media (GDM). The GDM typically comprise a mesoporous carbon layer (MPL) on top of a porous carbon-fiber gas diffusion layer (GDL) which are both wetted with polytetrafluoroethylene (PTFE) to modify their water retention. In a PEMFC, the GDM are compressed to either side of the catalyst coated membrane. The GDM are active in the fuel cell transport processes including electron and heat conduction, water removal, and distributing reactant gases to the catalyst layers, which affects the electrochemistry in the catalyst layers. These transport phenomena rely on both the properties of the GDM solid phase and its voids, making optimization of GDM material properties challenging. The majority of reports in the PEMFC literature addressing GDM focus solely on the cathode, since water is produced at this electrode and its ineffective removal can block active sites and occlude O2 diffusion. Most research reports use symmetrical anode and cathode GDM. To date, there has been less discussion on the role of the anode GDM or how anode and cathode GDM properties can be selected in concert to increase fuel cell power output, despite that a significant amount of water in a fuel cell is rejected to the anode.We consider that anode and cathode GDM properties, such as air permeability, must be chosen in unison to improve cell water management. In our previous work, we used X-ray computed tomography to observe that dry-laid, non-woven, Freudenberg GDM maintain large void volume while permitting high compressive stress, ultimately resulting in lower contact and ohmic resistances and better mass transport compared to another distinct class of GDM (wet-laid, SGL).1 In this work, we make a range of PEMFCs using a suite of Freudenberg GDM to study the influence of anode and cathode GDM air permeability and how these properties may be paired to improve cell hydration and increase fuel cell power production in a broad range of operating conditions. Fuel cells are characterized with cyclic voltammetry, electrochemical impedance spectroscopy (EIS), gravimetric analysis, and limiting current measurements to quantify the sources of mass transport resistance. Gradients of GDM material properties from anode to cathode improve cell hydration and facilitate water removal to reduce mass transport resistances and enable higher power operation. 1. “The Role of Compressive Stress on Gas Diffusion Media Morphology and Fuel Cell Performance,” R. W. Atkinson III, Y. Garsany, B. D. Gould, K. E. Swider-Lyons, I. V Zenyuk, ACS Applied Energy Materials, 2017, 1 (1), 191–201.

Complementary approaches to tooth wear analysis in Tritylodontidae (Synapsida, Mammaliamorpha) reveal a generalist diet.

Stereoscopic microwear and 3D surface texture analyses on the cheek teeth of ten Upper Triassic to Lower Cretaceous tritylodontid (Mammaliamorpha) taxa of small/medium to large body size suggest that all were generalist feeders and none was a dietary specialist adapted to herbivory. There was no correspondence between body size and food choice. Stereomicroscopic microwear analysis revealed predominantly fine wear features with numerous small pits and less abundant fine scratches as principal components. Almost all analyzed facets bear some coarser microwear features, such as coarse scratches, large pits, puncture pits and gouges pointing to episodic feeding on harder food items or exogenous effects (contamination of food with soil grit and/or dust), or both. 3D surface texture analysis indicates predominantly fine features with large void volume, low peak densities, and various stages of roundness of the peaks. We interpret these features to indicate consumption of food items with low to moderate intrinsic abrasiveness and can exclude regular rooting, digging or caching behavior. Possible food items include plant vegetative parts, plant reproductive structures (seeds and seed-bearing organs), and invertebrates (i.e., insects). Although the tritylodontid tooth morphology and auto-occlusion suggest plants as the primary food resource, our results imply a wider dietary range including animal matter.

Estimation of the Quantity of Water in the Abandoned Underground Mine of Gold Fields Ghana Limited Tarkwa: A Potential Source to Augment Water Supply to Tarkwa Municipality

The Tarkwa district is an important gold mining area in the Southwestern part of Ghana. The main source of potable water supply to the Tarkwa Nsuaem Municipality is from the Bonsa River treatment plant managed by the Ghana Water Company Limited (GWCL). The River is under threat from serious contamination by illegal mining ("galamsey") activities within its catchment area. Consequently, the amount of water supplied to the Municipality has not kept pace with its growing population due to increasing treatment cost and supply difficulties. The need to find alternative and sustainable sources of potable water supply to augment that from GWCL to the Municipality has become imperative. A large void volume created as a result of the abandoned underground mine operated by Gold Fields Ghana Limited (GFGL), after its closure in 1999 has flooded. This potential water resource is being pumped out daily, and wasted, sometimes spilling-over to low lying areas around the mine when allowed to reach its decant level. This study estimated the quantity of water in the Abontiakoon Vertical Shaft (AVS) which is part of the large underground void using survey production figures and post-closure void filling parameters resulting in 2.8 x 106 m3 and 2.9 x 106 m3 respectively. The rate of recharge to the underground water was also estimated to ascertain the sustainability of the void water should it be considered for use by employing the model of predicting rebound on “void filling” basis and average dewatering rate before closure at 2 535 m3/day and 2 618 m3/day respectively; indicating that recharge to the AVS reservoir is about 6 x 106 gal/day or 30% of current daily water supply deficit in the TNM. The estimated potential volume of mine water in storage in the entire Tarkwa underground void is 32 x106 m3. Two samples of the mine water were taken in November 2011 and February 2015 for quality analysis, in order to have a fair knowledge of the water quality parameters. The quality of the underground water was found to be potentially good, and not likely to cause any health threats, or water quality problems. Depth sampling is recommended to determine the chemical profile of the reservoir. Keywords: Reservoir, Municipality, Bonsa River, Contamination, Tarkwa