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Fabrication of titanium components is very cost intensive, partly due to the complex machining and limited recyclability of waste material. For electrochemical applications, the excellent corrosion resistance of pure titanium is of high importance, whereas medium mechanical strength of fabricated parts is sufficient for such a use case. For smaller parts, metal fused filament fabrication MF3 enables the fabrication of complex metallic structures densified during a final sintering step. Pure titanium can be processed to near net shape geometries for electrochemical applications if the parameters and the atmosphere during sintering are carefully monitored. Herein, the influence of thermal debinding and sintering parameters on the fabrication of high density pure titanium using MF3 is investigated. Particular focus is placed on enhancing sintered density while limiting impurity uptake to conserve the high chemical purity of the initial powder material. Relative densities of 95 are repeatedly reached inside the bulk of the samples. An oxygen content of 0.56 amp; 8201;wt as a result of vacuum processing induces the formation of the retained amp; 945; Ti phase 925 amp; 8201;HV0.2 inside the amp; 945; matrix 295 amp; 8201;HV0.2 . Fabricated parts exhibit high mechanical strength, albeit reduced elongation due to remaining pores, and, in terms of electrochemistry, enhanced stability toward anodic dissolution

Powder extrusion moulding (PEM) is a versatile and cost-effective technology for producing bi-dimensional shapes, (e.g. tubes and profiles) from metals, ceramics and cermets. PEM quality is affected by powder content; therefore, three highly-filled polymeric compounds containing 50, 55, 60 vol% tool steel powder were prepared and extruded to profiles. Extruded parts were debound in cyclohexane and sintered in forming gas (Ar + 5% H2) to obtain dense, sintered parts. The dimensional stability, the shrinkage and the hardness were measured. Minimum shrinkage and higher dimensional stability were obtained when the powder content was the highest (60 vol%). Specimens with 50 vol% powder had the highest hardness due to the initial higher binder content and resulting carbon content.

By using filaments comprising metal or ceramic powders and polymer binders, solid metal and ceramic parts can be created by combining low-cost fused filament fabrication (FFF) with debinding and sintering. In this work, we explored a fabrication route using a FFF filament filled with 316 L steel powder at 55 vol.-%. We investigated the printing, debinding and sintering parameters and optimized them with respect to the mechanical properties of the final part. Special focus was placed on debinding and sintering in order to obtain components of low residual porosity. Solvent debinding of the printed green bodies created an internal network of interconnected pores and was followed by thermal debinding. Thermal debinding allowed for complete removal of the remaining binder and produced mechanically stable brown parts. Sintering at 1360 °C provided densification of the parts and generated nearly isotropic linear shrinkage of about 20%. Using optimized parameters, it was possible to fabricate 316 L steel components with a density greater than 95% via the material extrusion additive manufacturing, debinding and sintering route, with achievable deflections in a 3-point bending test similar to rolled sheet material, albeit at lower strength.

Environmental nanoparticles found in soil systems and biosolids may pose a considerable risk to groundwater quality as contaminant carriers. Little effort has been invested in the characterization of natural nanocolloids compared to corresponding macrocolloids. This study involved physicochemical, mineralogical, and morphological characterizations of nanocolloids and macrocolloids fractionated from three Kentucky soils and one biosolid. Particle size and morphology were investigated using scanning/transmission electron microscopy and dynamic light scattering. Mineralogical composition was determined by X-ray diffraction and thermogravimetric and Fourier-transform infrared spectroscopy analyses. Zeta potentials and cation exchange capacities assessed surface charge and chemical reactivity. The estimated average hydrodynamic diameter of nanoparticles was nearly twice the ideal 100 nm range, apparently due to irregular particle shapes and partial aggregation. Nanoparticles were also found attached to surfaces of macrocolloids, forming macro-nano aggregates and obscuring some of their physical and chemical characteristics. However, nanocolloids exhibited greater surface reactivity, likely due to their smaller size, poor crystallinity, and morphological shape distortions. In spite of some behavior modification due to nanoaggregation phenomena, nanocolloids appeared to be much more potent vectors of contaminant transport in subsurface environments than their macrosize fractions. Nevertheless, their heterogeneous nature brings to light important considerations in addressing pollution prevention and remediation challenges.

Due to their enhanced stability and contaminant transport potential, environmental nanoparticles derived from soil and biosolid materials may pose a considerable risk to groundwater quality. Very little information exists on the stability and transportability of environmental or natural nanocolloids in the presence of As, Se, Pb and Cu contaminants, all of which are considered to represent substantial threats to human and animal populations through groundwater contamination. This study involved stability settling experiments of nanocolloids (NCs) ( mixed > kaolinitic > biosolid. Among the nano-fractions, the smectitic and kaolinitic colloids demonstrated lower stability than the MCs, but higher than those of the mixed and biosolid fractions. Physicochemical characterizations indicated that extensive organic carbon surface coatings and higher Al/Fe:Si ratios may have induced higher stability in the NC fractions, but their overall stability may also have been hindered in some cases by nano-aggregation phenomena.

Limited information exists on natural nanocolloid sorption behavior of As, Se, Cu and Pb in the environment. They are expected to have variable competitive sorption characteristics depending on size and composition and may transport elevated contaminant loads into surface and ground waters. A comprehensive characterization of their interactions with contaminants could provide a better understanding of the risks they pose to the environment. This study evaluated the sorption behavior of soil and biosolid nano- and macro-colloids with different mineralogical compositions for As, Se, Cu, and Pb contaminants. Single- and multi-contaminant Freundlich isotherms were us- ed to evaluate sorption affinity for the contaminants among the different colloid sizes and compositions. Sorption trends based on size indicated greater affinity for As and Cu by the smectitic and kaolinitic nanocolloids, greater affinity for Pb by the kaolinitic nanocolloids, and greater affinity for As, Se and Pb by bio-nanocolloids over corresponding macrocolloid fractions. Both, single- and multi-contaminant isotherms indicated sorption preferences for cation over anion contaminants, but with somewhat contrasting sequences depending on size and composition. Multi-contaminant isotherms generally predicted greater sorption affinities likely due to bridging effects, particularly for anionic contaminants. Surface properties such as zeta potentials, cation exchange capacity (CEC), surface area (SA), organic carbon (OC), and OC:SA significantly but variably affected sorption characteristics among the differing colloid sizes and compositions. Colloid zeta potential and pH shifts in the presence of different contaminant loads suggested prevalence of inner sphere bonding mechanisms for sorption of cation contaminants by mineral colloids and outer sphere sorption for cation and anion contaminants by bio-colloids.

Appalachian mountain wetlands are uncommon and diverse ecosystems; however, they are often susceptible to extensive alteration or destruction due to coal mining, highway construction, and quarrying. This study aimed to determine vegetation composition at three pristine wetlands and establish relationships with previously reported hydrologic, edaphic, and porewater characteristics to provide baseline data that could enhance wetland mitigation or restoration projects. Herbaceous vegetation was assessed by visually estimating percent cover for bryophyte and vascular species and by determining stem density for vascular taxa using 1 m2 quadrats located along transects. Multiple response permutation procedures (MRPPs) based upon importance values confirmed that species composition differed significantly (P < 0·001) among the sites. Nonmetric multi-dimensional scaling (NMDS) indicated that soil moisture conditions during the fall, soil chemistry, and porewater chemical composition influenced plant community composition. The first wetland (Martins Fork) was primarily dominated by Osmunda cinnamomea, Osmunda regalis, and Sphagnum palustre in response to drier soil during the fall season, higher soil pH, and weakly minerotrophic soil and porewater. The second wetland (Kentenia) was overwhelmingly dominated by S. palustre due to lower soil pH and persistently high water levels. Vegetation at the third wetland (Four Level) was distinguished by strongly dominant Scirpus polyphyllus and Glyceria striata and responded to higher soil and porewater Ca, Mg, and P concentrations as well as a light intensity gradient. The diverse vegetation and physico-chemical characteristics indicate that these sites, although small in size, support regional biodiversity and are potential reference wetlands. Copyright © 2011 John Wiley & Sons, Ltd.

Redox potentials (Eh) were monitored bimonthly and porewater chemistry was analyzed seasonally at three slightly-acidic, high-elevation Kentucky wetlands that differed in hydrology, parent materials, and vegetation. At all sites, Eh values were below 300 mV, which indicated that reducing conditions persisted within the upper 90 cm and fluctuated mainly within the range of iron and sulfate reduction. Significant relationships of Eh values with depth were observed only at the Martins Fork wetland, where precipitation was the primary water source. The strongest and most stable reducing conditions, observed at the Kentenia site, reflected consistently high water levels, which were sustained by ground water. The third wetland (Four Level) was distinguished by irregular Eh fluctuations coinciding with strong seasonal ground-water upwelling. Although Fe3+ and SO4 2− were the primary terminal electron acceptors in all wetlands, porewater chemistry also varied significantly by season and soil depth in response to piezometric water level fluctuations. Additional factors that influenced porewater chemistry included: (1) the presence of limestone parent materials that affected porewater pH, Ca2+, and Mg2+; and (2) the prevalence of sphagnum moss or graminoid species that influenced dissolved organic carbon, CO2, and CH4. Results from this study indicated the diverse range and importance of multiple factors in controlling biogeochemical processes and properties in small, high-elevation Appalachian wetlands.

Hydrologic patterns and soil characteristics were investigated at three high-elevation wetlands in southeastern Kentucky, Martins Fork, Kentenia, and Four Level. Despite below-normal precipitation, water tables at all sites remained within 35 cm of the surface and fluctuated seasonally with peak heights during early spring. Seasonal precipitation contributed substantially to Martins Fork hydrology, while ground water was the primary hydrologic source for Kentenia and Four Level. Vertical hydraulic gradients varied among the sites. Martins Fork was distinguished by strong seasonal downwelling, while Kentenia and Four Level exhibited upwelling and downwelling patterns. All sites exhibited prominent soil hydromorphic features immediately below the surface horizon, moderate organic carbon content (< 6.5%), and a pH range between 4.4 and 6.2 according to the buffering capacities of local lithologies. The sites were dominated by sandy loam texture and siliceous mineralogy, reflecting the influence of s...

The major question investigated is whether it is possible to accurately forecast selected crimes 1 month ahead in small areas, such as police precincts. In a case study of Pittsburgh, PA, we contrast the forecast accuracy of univariate time series models with naive methods commonly used by police. A major result, expected for the small-scale data of this problem, is that average crime count by precinct is the major determinant of forecast accuracy. A fixed-effects regression model of absolute percent forecast error shows that such counts need to be on the order of 30 or more to achieve accuracy of 20% absolute forecast error or less. A second major result is that practically any model-based forecasting approach is vastly more accurate than current police practices. Holt exponential smoothing with monthly seasonality estimated using city-wide data is the most accurate forecast model for precinct-level crime series.

Slaking experiments were conducted of fragipan clods immersed in solutions of poultry manure, aerobically digested biosolid waste (ADB), fluidized bed combustion byproduct (FBC), D-H2O, CaCO3, NaF, Na-hexa-metaphosphate, and ryegrass root biomass. The fragipan clods were sampled from the Btx horizon of an Oxyaquic Fragiudalf in Kentucky. Wet sieving aggregate analysis showed significantly better fragmentation in the NaF, Na-hexa-metaphosphate, and ryegrass root solutions with a mean weight diameter range of 15.5–18.8 mm compared to the 44.2–47.9 mm of the poultry manure, ADB, and FBC treatments. Dissolved Si, Al, Fe, and Mn levels released in solution were ambiguous. The poor efficiency of the poultry manure, ADB, and FBC treatments was attributed to their high ionic strength, while the high efficiency of the NaF, Na-hexa-metaphosphate, and rye grass root solutions to their high sodium soluble ratio (SSR). A slaking mechanism is proposed suggesting that aqueous solutions with high SSR penetrate faster into the fragipan capillaries and generate the critical swelling pressure and shearing stress required to rupture the fragipan into several fragments. Additional fragmentation occurs in a followup stage during which potential Si, Al, Fe, and Mn binding agents may be released into solution. Field experiments testing these findings are in progress.

The concentration of caseins and serum proteins in bovine skimmilk decreased when cows were maintained under the prolonged influence of oxytocin. Resolution of the components of these fractions by disc electrophoresis indicated that α -casein and α -lactalbumin decreased during forced milk release whereas β -casein and blood serum albumin increased.