Photoreductive Dissolution of Iron Oxides Trapped in Ice and Its Environmental Implications

The availability of iron has been thought to be a main limiting factor for the productivity of phytoplankton and related with the uptake of atmospheric CO_2 and algal blooms in fresh and sea waters. In this work, the formation of bioavailable iron (Fe(II)_(aq)) from the dissolution of iron oxide particles was investigated in the ice phase under both UV and visible light irradiation. The photoreductive dissolution of iron oxides proceeded slowly in aqueous solution (pH 3.5) but was significantly accelerated in polycrystalline ice, subsequently releasing more bioavailable ferrous iron upon thawing. The enhanced photogeneration of Fe(II)_(aq) in ice was confirmed regardless of the type of iron oxides [hematite, maghemite (γ-Fe_2O_3), goethite (α-FeOOH)] and the kind of electron donors. The ice-enhanced dissolution of iron oxides was also observed under visible light irradiation, although the dissolution rate was much slower compared with the case of UV radiation. The iron oxide particles and organic electron donors (if any) in ice are concentrated and aggregated in the liquid-like grain boundary region (freeze concentration effect) where protons are also highly concentrated (lower pH). The enhanced photodissolution of iron oxides should occur in this confined boundary region. We hypothesized that electron hopping through the interconnected grain boundaries of iron oxide particles facilitates the separation of photoinduced charge pairs. The outdoor experiments carried out under ambient solar radiation of Ny-Ålesund (Svalbard, 78°55′N) also showed that the generation of dissolved Fe(II)_(aq) via photoreductive dissolution is enhanced when iron oxides are trapped in ice. Our results imply that the ice(snow)-covered surfaces and ice-cloud particles containing iron-rich mineral dusts in the polar and cold environments provide a source of bioavailable iron when they thaw

Digital Rule of Thumb: A Natural Experiment on Autocomplete in Search Engines

Search engines are an essential part of our lives. However, we do not fully understand what affects users\u27 search inputs. One of the most notable features affecting search inputs is autocomplete, an intelligent agent suggesting queries while typing. Understanding the impact of autocomplete helps eCommerce companies retain customers; examining its impact is difficult since all search engines have adopted it, and experiments are risky for firms. We overcome the challenges by leveraging a novel natural experiment of an eCommerce company. Our preliminary results suggest that the deactivation of autocomplete for the incorrect keyword led to a substantial drop in website visits in the PC channel compared to the mobile channel. In addition, website visits substantially shifted from the incorrect keyword to the correct keyword in the mobile channel but not in the PC environment. This short paper is expected to shed new light on our understanding of autocomplete\u27s impact

A Nonlinear Optimization Model of Advertising Budget Allocation across Multiple Digital Media Channels

The goal of advertisers in the digital marketing industry is to optimize their advertising budgets. Such a budget allocation problem plays a key role in maximizing advertising performance from different marketing channels under planned advertising investment. This study aimed to design a budget-performance-based nonlinear programming model to find an optimized solution for the advertising budget allocation problem. The empirical analysis results of a leading e-business company’s advertising performance data show that the proposed non-LP model generates an optimized solution. The proposed model allows marketers to simulate expected advertising returns, such as conversions or revenues from different channels within their budget constraints

EFFECTS OF CONTACT SURFACE PROPERTIES ON MULTI-FINGER FORCE PRODUCTION TASKS IN HUMANS

The purpose of the current study was to investigate the effect of contact surface properties, which presumably determine the level of stimulation on the cutaneous receptors, on multifinger force production and synergic actions of finger forces. The framework of the uncontrolled manifold (UCM) hypothesis was used to quantify indices of multi-finger synergies stabilizing total force in normal and tangent directions as well as the direction of resultant force (i.e., force angle) during steady-state force production. There was significant effect of contact surface on the magnitude of maximal voluntary contraction force. Also, there was a significant effect of the contact surface on the indices of force-direction (i.e., force angle) stabilizing synergies meaning that the stimulation on the cutaneous receptors could be an effective way to enhance the abili to organize the direction of finger forces

DIFFERENCES OF POSTURE ON PUSH-OFF PHASE BETWEEN ACTUAL SPEED SKATING AND SLIDE-BOARD TRAINING

The slide-board training is a feasible technology to exercise skating during the off-season. While slide-board is much different from ice surface of the actual skating situation, it may distort actual skating posture. The purpose of this study was to analyze the differences in posture during push-off phase between an actual speed skating condition and on slideboard. The result showed that on the slide-board distance between two feet were shorter, so were the rotation angles of both feet, the hip angle was lower during the whole phase, while knee and ankle angles were higher. In conclusion, the restriction of the space on slide-board affected the position and rotation of both stable and push-off feet as well as the joint extension of the stable leg. Hence, the structural design of slide-board needs to be improved to facilitate the extension of knee and ankle in the medial-lateral direction

Effect of Anticipatory Shooting Strategy on Performance Consistency in Skilled Elite Archer

PURPOSE This study examined the effect of anticipatory control strategies on stable upright posture and consistency in archery performance among skilled elite archers. METHODS Nine skilled archery players participated in this study and performed repeated shooting trials under two different shooting conditions: clicker and non-clicker. In the clicker condition, archers shot in response to clicker signals, whereas in the non-clicker condition, they used an anticipatory strategy to determine shooting time in a self-paced manner without using the clicker. A motion capture system with six infrared cameras was used to measure the coordinates of the bow and archers’ hands, which were then used to calculate the aiming precision index and draw-related variables. Electromyography of the lower leg muscles and the center of pressure (COP) were also analyzed for a short period immediately before release to determine the differences in anticipatory postural adjustments (APAs) between the two shooting conditions. RESULTS The non-clicker condition resulted in a relatively short drawing duration and better precision index. The COP speed rapidly increased immediately before the release (i.e., APAs), and the rate of increase was lower in the non-clicker condition than in the clicker shooting condition. Furthermore, smaller APAs were significantly correlated with better-aiming precision in the non-clicker condition. CONCLUSION These findings suggest that using an anticipatory strategy rather than reacting to a clicker can improve archery performance consistency by reducing APA and ensuring a stable shooting posture. This strategy can be used in archery training to predict clicker signals during the aim-release stage

Immobilization of Lead in Contaminated Firing Range Soil Using Biochar

Soybean stover-derived biochar was used to immobilize lead (Pb) in military firing range soil at a mass application rate of 0 to 20 wt.% and a curing period of 7 days. The toxicity characteristic leaching procedure (TCLP) was performed to evaluate the effectiveness of the treatment. The mechanism responsible for Pb immobilization in military firing range soil was evaluated by scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) and x-ray absorption fine structure (XAFS) spectroscopy analyses. The treatment results showed that TCLP Pb leachability decreased with increasing biochar content. A reduction of over 90 % in Pb leachability was achieved upon treatment with 20 wt.% soybean stover-derived biochar. SEM-EDX, elemental dot mapping and XAFS results in conjunction with TCLP leachability revealed that effective Pb immobilization was probably associated with the pozzolanic reaction products, chloropyromorphite and Pb-phosphate. The results of this study demonstrated that soybean stover-derived biochar was effective in immobilizing Pb in contaminated firing range soil

Open-top axially swept light-sheet microscopy

Open-top light-sheet microscopy (OT-LSM) is a specialized microscopic technique for high throughput cellular imaging of large tissue specimens including optically cleared tissues by having the entire optical setup below the sample stage. Current OT-LSM systems had relatively low axial resolutions by using weakly focused light sheets to cover the imaging field of view (FOV). In this report, open-top axially swept LSM (OTAS-LSM) was developed for high-throughput cellular imaging with improved axial resolution. OTAS-LSM swept a tightly focused excitation light sheet across the imaging FOV using an electro tunable lens (ETL) and collected emission light at the focus of the light sheet with a camera in the rolling shutter mode. OTAS-LSM was developed by using air objective lenses and a liquid prism and it had on-axis optical aberration associated with the mismatch of refractive indices between air and immersion medium. The effects of optical aberration were analyzed by both simulation and experiment, and the image resolutions were under 1.6 & micro;m in all directions. The newly developed OTAS-LSM was applied to the imaging of optically cleared mouse brain and small intestine, and it demonstrated the single-cell resolution imaging of neuronal networks. OTAS-LSM might be useful for the high-throughput cellular examination of optically cleared large tissues

High performance Ge nanowire anode sheathed with carbon for lithium rechargeable batteries

We present a single crystalline Ge nanowire anode material sheathed with carbon prepared by a solid-liquid solution method. The composite electrode composed of Ge nanowires shows impressive electrochemical properties, exhibiting a very high reversible charge capacity (after lithium removal) of 963 mA h g(-1) with a coulombic efficiency of 91%.close11810