Dynamic Uplift Scenarios for Floating Ice

Three uplift scenarios in the forced dynamics of floating ice are studied. Linear, quadratic, and square-root uplift forcing functions are considered and the associated uplift displacement functions are computed numerically. In each case, the uplift forcing is known and the displacement at the point of forcing is unknown. This is the so-called “direct” problem. In essence, this study is aimed at learning more about the “indirect” or inverse problem, where the uplift displacement function is known and the forcing is unknown. A model problem, that is able to be solved in closed form for each of the three forcing functions considered, is used to verify the numerical calculations. By curve fitting the relative error between the model problem and the actual uplift problem, a general modus operandi is arrived at for deriving approximate expressions for the otherwise intractable uplift displacement. These approximate expressions satisfy the required initial conditions and are shown to be accurate.     

Wood Members Strengthened with Mechanically Fastened FRP Strips

The demand for a rapid technique to strengthen existing wood bridge structural elements is evident in military and civilian sectors. An experimental program was undertaken to evaluate the feasibility of increasing the flexural strength of Southern Pine wood members using mechanically fastened fiber-reinforced polymer (FRP) strips. Three control specimens and twelve composite members were fabricated using two FRP material types with varying fastener spacing and tested to failure. The experimental results show that the proposed strengthening technique induced a gradual failure of the composite members and increased ultimate moment, initial stiffness, and ductility over that found for the control specimens. Increased fastener spacing decreased member ultimate moment, initial stiffness, and ductility ratio. The moisture content of the wood material greatly affected the ductility ratio of the wood members.     

Reduction of U(VI) by Fe(II) in the presence of hydrous ferric oxide and hematite: effects of solid transformation, surface coverage, and humic acid

Fe(II) was added to U(VI)-spiked suspensions of hydrous ferric oxide (HFO) or hematite to compare the redox behaviors of uranium in the presence of two different Fe(III) (oxyhydr)oxides. Experiments were conducted with low or high initial sorption density of U(VI) and in the presence or absence of humic acid (HA). About 80% of U(VI) was reduced within 3 days for low sorbed U(VI) conditions, with either hematite or HFO. The {Fe(3+)} in the low U(VI) experiments at 3 days, based on measured Fe(II) and U(VI) and the assumed presence of amorphous UO(2(s)), was consistent with control by HFO for either initial Fe(III) (oxyhydr)oxide. After about 1 day, partial re-oxidation to U(VI) was observed in the low sorbed U(VI) experiments in the absence of HA, without equivalent increase of dissolved U(VI). No reduction of U(VI) was observed in the high sorbed U(VI) experiments; it was hypothesized that the reduction required sorption proximity of U(VI) and Fe(II). Addition of 5mg/L HA slowed the reduction with HFO and had less effect with hematite. M?ssbauer spectroscopy (MBS) of (57)Fe(II)-enriched samples identified the formation of goethite, hematite, and non-stoichiometric magnetite from HFO, and the formation of HFO, hydrated hematite, and non-stoichiometric magnetite from hematite.     

Effects of wastewater effluent organic materials on fouling in ultrafiltration

The objective was to determine the effects of wastewater effluent organic materials (EfOM) on fouling of ultrafilters (100kDa polyethersulfone (PES)). EfOM constituents were sequentially removed, first by removing particles down to the approximate ultrafilter pore size and then by removing dissolved EfOM based on functionality. Particles and colloids >20nm accounted for 19% of total organic carbon (TOC), including 96% of EfOM >100kDa. Removal of particles and colloids resulted in increased fouling, attributed to increased contact of dissolved EfOM with the membrane. Hydrophobic and hydrophilic (HPO/HPI) acids were 22% of total EfOM, and accounted for nearly all of the fouling. HPO/HPI base/neutrals were 59% of EfOM, but did not cause any significant fouling. Although HPO/HPI base/neutrals did not cause any fouling, they were the dominant EfOM constituent at the surface of fouled and then hydraulically cleaned membranes, as measured by attenuated reflectance infrared spectroscopy. Since the filtration runs were short, the effects of HPO/HPI base/neutrals on long-term fouling should be further investigated, but these results cast doubt on the presumption that organic materials that are identified during membrane autopsies are necessarily a primary cause of fouling. These results also indicate that wastewater EfOM should be treated to remove HPO/HPI acids prior to membrane filtration.     

A model-based evaluation of sorptive reactivities of hydrous ferric oxide and hematite for U(VI)

The sorption of uranyl onto hydrous ferric oxide (HFO) or hematite was measured by discontinuously titrating the suspensions with uranyl at pH 5.9, 6.8, and 7.8 under Pco2 = 10(-35)atm (sorption isotherms). Batch reactors were used with equilibration times up to 48 days. Sorption of 1 microM uranyl onto HFO was also measured versus pH (sorption edge). A diffuse double layer surface complexation model was calibrated by invoking three sorption species that were consistent with spectroscopic evidence for predominance of bidentate complexes at neutral pH and uranyl-carbonato complexes: > SOH:UO2OH(+1), (> SO)2: UO2CO3(-2), and (> SO)2:(UO2)3(OH)5(-1). The model was consistent with previously published isotherm and edge data. The model successfully predicted sorption data onto hematite, only adjusting for different measured specific surface area. Success in application of the model to hematite indicates that the hydrated surface of hematite has similar sorptive reactivity as HFO.     

Solubility of hematite revisited: effects of hydration

Measured pH and dissolved ferric iron concentration ([Fe(III)diss]) in contact with well-characterized hematite indicated an equilibrium with hematite immediately after synthesis, but [Fe(III)diss] increased with hydration time to be consistent with the predicted solubility of goethite or hydrous ferric oxide (HFO), hydrated analogues of hematite. X-ray diffraction did not detect structural modification of hematite after 190 days of hydration, but M?ssbauer spectroscopy detected hydration that penetrated several crystalline layers. When the hematite suspension was diluted with water, solids were invariably identified as hematite, but [Fe(III)diss] and pH indicated an equilibrium with goethite or HFO. This is the first experimental confirmation that the interfacial hydration of anhydrous hematite results in higher solubility than predicted by bulk thermodynamic properties of hematite. Correspondence of the results with previously published measurements and implications for environmental chemistry of ferric oxides are also discussed.     

Effect of natural organic matter on zinc inhibition of hematite bioreduction by Shewanella putrefaciens CN32

The effect of zinc on the biological reduction of hematite (alpha-Fe2O3) by the dissimilatory metal-reducing bacterium (DMRB) Shewanella putrefaciens CN32 was studied in the presence of four natural organic materials (NOMs). Experiments were performed under non-growth conditions with H2 as the electron donor and zinc inhibition was quantified as the decrease in the 5 d extent of hematite bioreduction as compared to no-zinc controls. Every NOM was shown to significantly increase zinc inhibition during hematite bioreduction. NOMs were shown to alter the distribution of both biogenic Fe(II) and Zn(II) between partitioned (hematite and cell surfaces) and solution phases. To further evaluate the mechanism(s) of NOM-promoted zinc inhibition, similar bioreduction experiments were conducted with nitrate as a soluble electron acceptor, and hematite bioreduction experiments were conducted with manganese which was essentially non-inhibitory in the absence of NOM. The results suggest that Me(II)-NOM complexes may be specifically inhibitory during solid-phase bioreduction via interference of DMRB attachment to hematite through the formation of ternary Me(II)-NOM-hematite complexes.     

Process control and pulsed laser deposition of materials

Abstract

Pulsed-laser deposition (PLD) is a very powerful and rapid deposition technique, which can produce exceptional-quality thin films. Although PLD has tremendous versatility and potential, PLD capabilities are still constrained by a lack of process control. At the Air Force Research Laboratory on-site at Wright-Patterson AFB, we are developing in-situ/real-time control methodologies for PLD and other thin-film deposition processes. We have identified appropriate sensors for closed-loop feedback control and utilized them with YBa₂Cu₃O_7-x (YBCO) to identify critical process control parameters. Control instrumentation has recently been improved by the addition of moveable fixed-position plume-emission sensors. The reproducibility of YBCO film quality increased significantly when process control was applied to PLD processing.

PLD process control techniques were applied during simulated and actual BSTO depositions. A comparison of deposition control with the controlling sensor at different distances from the substrate heater position is discussed. Further process refinement using time-resolved spectral components of the PLD plume on subsequent film quality is also discussed.     

Development of a semi-permanent mascara technology

Many women would like their mascara beauty benefits to be available all day, every day. One way to address this desire is through a semi-permanent mascara technology that provides full mascara benefits of long, dark beautiful lashes for multiple days. To date, products promising multi-day benefits have acted more as either 'lash dyes', providing a lash darkening benefit but failing to provide fullness and length, or waterproof mascaras that do not maintain the initial beauty look over multiple days. Here, a formulation approach is described for a mascara product that is designed to be abrasion resistant, flexible and insoluble in soap and water so that the initial beauty look is maintained for multiple days. The new semi-permanent formula technology uses rosinate polymers that have a superior combination of flexibility, abrasion resistance and water and surfactant resistance. Based on principles used by the paint industry for creating durable films, the levels of the polymers and other non-volatile ingredients are balanced such that the product forms a continuous polymer film on the eyelash. Cryo-SEM is used to demonstrate that the new semi-permanent formula technology forms a film different from those formed by current mascara products. A stretch test and rub test are used to demonstrate that the new semi-permanent formula technology has superior flexibility and abrasion resistance to current mascara products. Finally, a multi-day consumer study with daily imaging of the eyes is used to demonstrate the superior wear performance of the new semi-permanent formula technology in actual usage.     

Back to the bones: do muscle area assessment techniques predict functional evolution across a macroevolutionary radiation?

Measures of attachment or accommodation area on the skeleton are a popular means of rapidly generating estimates of muscle proportions and functional performance for use in large-scale macroevolutionary studies. Herein, we provide the first evaluation of the accuracy of these muscle area assessment (MAA) techniques for estimating muscle proportions, force outputs and bone loading in a comparative macroevolutionary context using the rodent masticatory system as a case study. We find that MAA approaches perform poorly, yielding large absolute errors in muscle properties, bite force and particularly bone stress. Perhaps more fundamentally, these methods regularly fail to correctly capture many qualitative differences between rodent morphotypes, particularly in stress patterns in finite-element models. Our findings cast doubts on the validity of these approaches as means to provide input data for biomechanical models applied to understand functional transitions in the fossil record, and perhaps even in taxon-rich statistical models that examine broad-scale macroevolutionary patterns. We suggest that future work should go back to the bones to test if correlations between attachment area and muscle size within homologous muscles across a large number of species yield strong predictive relationships that could be used to deliver more accurate predictions for macroevolutionary and functional studies.