Single-Atomic-Layer Stanene on Ferromagnetic Co Nanoislands with Topological Band Structures.

Introducing magnetism to two-dimensional topological insulators is a central issue in the pursuit of magnetic topological materials in low dimensionality. By means of low-temperature growth at 80 K, we succeeded in fabricating a monolayer stanene on Co/Cu(111) and resolving ferromagnetic spin contrast by field-dependent spin-polarized scanning tunneling microscopy (SP-STM). Increases of both remanence to saturation magnetization ratio (Mr/Ms) and coercive field (Hc) due to an enhanced perpendicular magnetic anisotropy (PMA) are further identified by out-of-plane magneto-optical Kerr effect (MOKE). In addition to ultraflat stanene fully relaxed on bilayer Co/Cu(111) from density functional theory (DFT), characteristic topological properties including an in-plane s-p band inversion and a spin-orbit coupling (SOC) induced gap about 0.25 eV at the Γ̅ point have also been verified in the Sn-projected band structure. Interfacial coupling of single-atomic-layer stanene with ferromagnetic Co biatomic layers allows topological band features to coexist with ferromagnetism, facilitating a conceptual design of atomically thin magnetic topological heterostructures.

Fabrication and Imaging Monatomic Ni Kagome Lattice on Superconducting Pb(111).

Artificial fabrication of a monolayer Kagome material can offer a promising opportunity to explore exceptional quantum states and phenomena in low dimensionality. Here, we have systematically studied a monatomic Ni Kagome lattice grown on Pb(111) by scanning tunneling microscopy/spectroscopy (STM/STS) and density functional theory (DFT). Sawtooth edge structures with distinct heights due to subsurface Ni atoms have been revealed, leading to asymmetric edge scattering of surface electrons on Pb(111). In addition, a local maximum at about -0.2 eV in tunneling spectra represents a manifestation of characteristic phase-destructive flat bands. Although charge transfer from underlying Pb(111) substrate results in a vanishing magnetic moment of Ni atoms, the proximity-induced superconducting gap is slightly enhanced on the Ni Kagome lattice. In light of single-atomic-layer Ni Kagome lattice on superconducting Pb(111) substrate, it could serve as an ideal platform to investigate the interplay between Kagome physics and superconductivity down to the two-dimensional limit.

Proximity-Effect-Induced Anisotropic Superconductivity in a Monolayer Ni-Pb Binary Alloy.

A proximity effect facilitates the penetration of Cooper pairs that permits superconductivity in a normal metal, offering a promising approach to turn heterogeneous materials into superconductors and develop exceptional quantum phenomena. Here, we have systematically investigated proximity-induced anisotropic superconductivity in a monolayer Ni-Pb binary alloy by combining scanning tunneling microscopy/spectroscopy (STM/STS) with theoretical calculations. By means of high-temperature growth, the (33×33)R30o Ni-Pb surface alloy has been fabricated on Pb(111) and the appearance of a domain boundary as well as a structural phase transition can be deduced from a half-unit-cell lattice displacement. Given the high spatial and energy resolution, tunneling conductance (dI/dU) spectra have resolved the reduced but anisotropic superconducting gap ΔNiPb ≈ 1.0 meV, in stark contrast to the isotropic ΔPb ≈ 1.3 meV. In addition, the higher density of states at the Fermi energy (D(EF)) of the Ni-Pb surface alloy results in an enhancement of coherence peak height. According to the same Tc ≈ 7.1 K with Pb(111) from the temperature-dependent ΔNiPb and the short decay length Ld ≈ 3.55 nm from the spatially monotonic decrease of ΔNiPb, both results are supportive of a proximity-induced superconductivity. Despite a lack of a bulk counterpart, the atomically thick Ni-Pb bimetallic compound opens a pathway to engineer superconducting properties down to the two-dimensional limit, giving rise to the emergence of anisotropic superconductivity via a proximity effect.

Effects of ground and load on upper trapezius, biceps brachii muscle and hand forces in one- and two-wheeled wheelbarrow pushing.

This study examines the effects of ground surface, load, one- and two-wheeled wheelbarrow on muscular activities, hand force, and subject-perceived exertions while pushing a wheelbarrow in a straight line on a horizontal surface. The experimental results show that wheelbarrow load significantly affected muscular activities, hand force, and subject-perceived exertion. Additionally, different ground surfaces and wheelbarrow types also affected the muscular activities of the dominant hand; grass generated the highest muscle load and asphalt pavement generated the smallest muscle load. The user has to apply 57% and 23% more force in the vertical and horizontal direction while pushing one-vs. two-wheeled wheelbarrow. Muscular activity increased significantly in the dominant hand with the one-wheeled wheelbarrow compared with the two-wheeled wheelbarrow, suggesting that, in terms of muscle loads, the two-wheeled wheelbarrow is better than the one-wheeled wheelbarrow.

The acute effect of exposure to noise on cardiovascular parameters in young adults.

OBJECTIVE: In this study, an experiment was conducted to examine whether noise exposure produced acute changes in cardiovascular responses, and whether these responses differed based on psycho-acoustic parameters to noises of low to high intensity. METHODS: Thirty healthy subjects were enrolled. Three industrial noises were binaurally presented with a supra-aural earphone. The sound levels of noise were <55, 75, and 90 dB. Each noise was continued for 20 min and the electrocardiogram was simultaneously recorded. RESULTS: The results showed a statistically significant increase in systolic blood pressure (SBP) at the 90 dB sound level. The study estimated a blood pressure increase of 0.85 mmHg/10 dB and 0.71 mmHg/10 dB in SBP and diastolic blood pressure (DBP), respectively. These results suggest that exposure to noise, particularly high-frequency noise, negatively impacts blood pressure. The tonality and fluctuation strength of noise especially impacts systolic blood pressure. CONCLUSIONS: The psycho-acoustic parameters of noise should be considered when evaluating the impact of noise exposure.

Kinetics of nitrification in a fixed biofilm reactor using dewatered sludge-fly ash composite ceramic particle as a supporting medium.

A mathematical model system was derived to describe the kinetics of ammonium nitrification in a fixed biofilm reactor using dewatered sludge-fly ash composite ceramic particle as a supporting medium. The model incorporates diffusive mass transport and Monod kinetics. The model was solved using a combination of the orthogonal collocation method and Gear's method. A batch test was conducted to observe the nitrification of ammonium-nitrogen ([Formula: see text]-N) and the growth of nitrifying biomass. The compositions of nitrifying bacterial community in the batch kinetic test were analyzed using PCR-DGGE method. The experimental results show that the most staining intensity abundance of bands occurred on day 2.75 with the highest biomass concentration of 46.5 mg/L. Chemostat kinetic tests were performed independently to evaluate the biokinetic parameters used in the model prediction. In the column test, the removal efficiency of [Formula: see text]-N was approximately 96 % while the concentration of suspended nitrifying biomass was approximately 16 mg VSS/L and model-predicted biofilm thickness reached up to 0.21 cm in the steady state. The profiles of denaturing gradient gel electrophoresis (DGGE) of different microbial communities demonstrated that indigenous nitrifying bacteria (Nitrospira and Nitrobacter) existed and were the dominant species in the fixed biofilm process.

Effect of shoe heel height and total-contact insert on muscle loading and foot stability while walking.

BACKGROUND: Women wearing high-heeled shoes often complain of foot instability and low-back pain. Previous studies have demonstrated that using total-contact inserts (TCIs) in running shoes reduces impact on leg muscles and alters rearfoot motion. This study investigated how shoe heel height and use of TCIs in high-heeled shoes affect the wearer's rearfoot complex, muscle loading, and subjective comfort. METHODS: Fifteen inexperienced high heel wearers walked under 6 test conditions formed by the cross-matching of shoe insert (with and without TCI) and heel height (1.0, 5.1, and 7.6 cm) at a speed of 1.3 m/s. The measures of interest were rearfoot kinematics; muscle activities by electromyography (EMG) of the tibialis anterior (TA), medial gastrocnemius (MG), quadriceps (QUA), hamstrings (HAM), and erector spinae (ES); and subjective comfort rating by visual analogue scale for each test condition. RESULTS: The statistical results showed that elevated heel height significantly increased plantar flexion (P < .001) and inversion (P < .01) at heel strike, prolonged TA-MG co-contraction (P < .001) and QUA activation period (P < .001), and increased root mean square (RMS) EMG in all measured muscles (TA, MG, QUA, ES: P < .001; HAM: P < .01). The use of TCIs reduced the rearfoot inversion angle (P < .01) and RMS EMG in both QUA and ES muscles (P < .01) and increased comfort rating (P < .001). CONCLUSIONS: These findings suggest that wearing high-heeled shoes adversely affects muscle control and reduces loads in QUA and ES muscles. CLINICAL RELEVANCE: The use of a TCI may improve comfort rating and foot stability.

Optimization of nutritional compositions of growth medium for Chlorella sp. FJ3 growth kinetics in batch and continuous-flow photoreactors.

This study investigates improvement to culture medium for specific growth rate of Chlorella sp. FJ3 using a fractional factorial design for 32 experiments with six variable components. Six tested components were NaNO3 (0.5 or 3.0 g/l), K2HPO4 (0.01 or 0.06 g/l), MgSO4 7H2O (0.05 or 1.0 g/l), CaCl2 x 2H2O (0.01 or 0.06 g/l), ferric ammonium citrate (0.002 or 0.02 g/l) and NaCl (0.5 or 5.0 g/l). Magnesium sulphate and interaction between magnesium sulphate and ferric ammonium citrate were found to be critical for the cultivation of Chlorella sp. FJ3. The optimal concentrations of MgSO4 x 7H2O and ferric ammonium citrate were found to be 2.0 and 0.35 g/l, respectively. The concentration of carbonate (CO3(2-)) in effluent confirmed that the optimized culture medium was associated with a high carbonate utilization rate and specific growth rate during a transient period in batch and continuous-flow tests. The extent of growth of strain FJ3 in the optimized medium was 1.61 times greater than that in a non-optimized medium in the batch test. In the continuous-flow test, the maximum growth of Chlorella strain FJ3 in the optimized medium was 1.77 times higher than that in a non-optimized medium. The rate of CO3(2-) fixation in the non-optimized and the optimized media was 339 mg/l-day and 887 mg/l-day, respectively, in the steady state. These experimental and modelling results indicated that optimization of concentration in nutritional compositions in the culture medium enhanced the capacity of Chlorella sp. FJ3 for inorganic carbon fixation in batch and continuous-flow modes of photoreactors.

Adsorption with biodegradation for decolorization of reactive black 5 by Funalia trogii 200800 on a fly ash-chitosan medium in a fluidized bed bioreactor-kinetic model and reactor performance.

A non-steady-state mathematical model system for the kinetics of adsorption and biodegradation of reactive black 5 (RB5) by Funalia trogii (F. trogii) ATCC 200800 biofilm on fly ash-chitosan bead in the fluidized bed process was derived. The mechanisms in the model system included adsorption by fly ash-chitosan beads, biodegradation by F. trogii cells and mass transport diffusion. Batch kinetic tests were independently performed to determine surface diffusivity of RB5, adsorption parameters for RB5 and biokinetic parameters of F. trogii ATCC 200800. A column test was conducted using a continuous-flow fluidized bed reactor with a recycling pump to approximate a completely-mixed flow reactor for model verification. The experimental results indicated that F. trogii biofilm bioregenerated the fly ash-chitosan beads after attached F. trogii has grown significantly. The removal efficiency of RB5 was about 95 % when RB5 concentration in the effluent was approximately 0.34 mg/L at a steady-state condition. The concentration of suspended F. trogii cells reached up to about 1.74 mg/L while the thickness of attached F. trogii cells was estimated to be 80 µm at a steady-state condition by model prediction. The comparisons of experimental data and model prediction show that the model system for adsorption and biodegradation of RB5 can predict the experimental results well. The approaches of experiments and mathematical modeling in this study can be applied to design a full-scale fluidized bed process to treat reactive dye in textile wastewater.

Molecular weight distribution of organic matter by ozonation and biofiltration.

Molecular weight (MW) distribution of organic matter by ozonation and biofiltration was evaluated using gel chromatography. The MW distribution of organic matter by Sephadex G-25 was observed from groups 2 (MW = 1,029-7,031 g/mol) and 3 (MW = 303-1,029 g/mol) shifted to groups 2, 3 and 4 (MW < 303 g/mol) under ozone doses of 0.1 and 0.4 mg O3/mg total organic carbon (TOC). The shift in MW increases as ozone dosage increases. Biofiltration effectively degraded the organic molecule of group 2; however, the biofiltration only slightly degraded the organic molecule of group 4. Increased ozone dose destroyed functional groups C═C in phenolic and C-O in alcoholic compounds and increased UV-insensitive biodegradable organic carbon for subsequent biofiltration. Biofiltration effectively degraded organic compounds of alcohols and alkenes at an ozone dose of 0.1 mg O3/mg TOC. Experimental approaches in this study can be applied to evaluate and diagnose the function of a full-scale process combining ozonation and biofiltration in drinking water treatment plants.

Effectiveness of leg movement in reducing leg swelling and discomfort in lower extremities.

Various occupations required that workers stand for long periods, causing discomfort and pain. This study considered the effectiveness of three leg movements in relieving discomfort of the lower extremities during long periods of standing at work. Ten paid male subjects with no history of problems of the lower extremities were enrolled in this study. They performed three leg movements on a hard floor while standing for 4 h in a laboratory setting. Each 1 h experimental test had two phases - 50 min of standing, followed by 10 min of rest. During the period of standing, one the following leg movements was made. No movement (no change in posture), ankle movement (twice, for 2 min each time), and hip movement (twice, for 2 min each time). Observations revealed that the three leg movements yielded different degrees of lower limb swelling. The percentage changes in thigh (1.22%) and shank (1.32%) circumferences were largest during prolonged standing without any movement and lowest during prolonged standing with ankle movement (0.61%) and hip movement (0.80%). The relationship between perceived discomfort and standing time was determined. The subjects perceived the most shank discomfort (5.8) during the 4 h test without any movement. Leg movement greatly influenced perceived discomfort of the shank. The results of this study suggested that workers should move their ankles and hips for a short period following prolonged standing for 30 min to reduce lower extremity discomfort.

Influence of shoe/floor conditions on lower leg circumference and subjective discomfort during prolonged standing.

Many occupations require workers to stand for prolonged periods, which can cause both discomfort and pain. This study examines the effects of different shoe and floor conditions on standing discomfort in the workplace and laboratory. Two experiments were conducted. Experiment 1 enrolled 10 subjects who performed a computer task under two floors and shoe conditions while standing for 4 h in a laboratory. Experiment 2 involved 14 subjects who stood for 4 h throughout their shift on two different floors in a real work situation (i.e., a field experiment). Analytical results demonstrate that floor type and time standing significantly affected subjective ratings for leg discomfort and circumferential shank measurements in both the laboratory and field studies. Shoe condition significantly affected subjective ratings for leg discomfort. We conclude that shoe/floor conditions and prolonged standing influence worker lower extremity discomfort during prolonged standing. These analytical findings suggest that common ergonomic interventions, such as modifying the flooring on which workers stand might some what alleviate leg edema for workers standing for 4 h shifts in laboratory and field settings. Nevertheless, prolonged standing for even 1 h without rest showed negative effects and should be avoided when possible.

Characteristics transformation of humic acid during ozonation and biofiltration treatment processes.

Characteristics transformation of humic acid extracted from natural water during the ozonation and biofiltration treatment processes was investigated based on the analyses of total organic carbon, UV absorbance, infrared spectroscopy, and gel permeation chromatography. With ozone doses of 1, 4, and 7 mg/L, high-molecular-weight humic acid was cleaved into low-molecular-weight particles and accumulated at group 6 (molecular weight < or = 4000 g/mole) on the Sephadex G-75 (Pharmacia Fine Chemicals, Uppsala, Sweden) fraction. Furthermore, the molecular-size distribution of organic compounds by Sephadex G-25 was shifted from groups 2 (molecular weight = 4000 to 400 g/mole) and 3 (molecular weight = 400 to 180 g/mole) to groups 2, 3, and 4 (molecular weight < or = 180 g/mole) under ozone doses of 1 and 4 mg/L. An increased ozone dose destroyed functional groups C=C and C-O of aromatic and phenolic compounds and increased UV-insensitive biodegradable organic carbon for subsequent biofiltration.

Effects of temperature and initial pH on biohydrogen production from food-processing wastewater using anaerobic mixed cultures.

This study attempted to determine the optimal temperature and initial cultivation pH by conducting a series of batch tests in stirred-tank bioreactor using fructose-producing wastewater as an organic substrate. The bioreactor temperature was controlled at 35-55°C with an initial pH of 4-8. Hydrogen production efficiency was assessed using specific hydrogen production potential (SHPP) and the maximum specific hydrogen production rate (SHPR(m)). Experimental results indicated that temperature and initial pH markedly affected SHPP and SHPR(m), volatile fatty acids distribution as well as the ratio of butyrate/acetate (BHu/HAc). Two-fold higher SHPP and SHPR(m) were obtained at thermophilic condition (55°C) than those at mesophilic condition (35°C). The optimal initial pH was 6 for hydrogen production with peak values of SHPP of 166.8 ml-H(2)/g-COD and SHPR(m) of 26.7 ml-H(2)/g-VSS-h for fructose-processing wastewater. Molasses-processing wastewater had a higher SHPP (187.0 ml-H(2)/g-COD) and SHPR(m) (42.7 ml-H(2)/gVSS-h) than fructose-processing wastewater at pH 6. The DGGE profiles indicated that molasses-processing wastewater is a better substrate than fructose-processing wastewater for growth of hydrogen-producing bacteria due to the high staining intensity of bands.

Influence of sulfur concentration on bioleaching of heavy metals from industrial waste sludge.

The bioleaching process, including acidification and solubilization of heavy metals, is a promising method for removing heavy metals from industrial waste sludge. Solubilization of heavy metals in industrial waste sludge is governed by adding elemental sulfur. A sulfur concentration exceeding 0.5% (w/v) inhibits sulfate production and the activity of acidophilic bacteria. Sulfate production was described well by a substrate inhibition expression in Haldane's kinetics. After 15 days of bioleaching, 79 to 81% copper, 50 to 69% lead, and 49 to 69% nickel were solubilized from sludge with a sulfur concentration of 0.5 to 1.0% (w/v). Experimental results indicated that the optimal sulfur concentration for the maximum solubilization rate of copper and nickel was 0.5% (w/v) and 1.0% (w/v) for lead. The profiles of denaturing gradient gel electrophoresis confirmed that indigenous acidophilic Acidithiobacilli (A. thiooxidans and A. ferrooxidans) existed and were the dominant species in the bioleaching process.

Modeling the performance of biodegradation of textile wastewater using polyurethane foam sponge cube as a supporting medium.

A pilot-scale fixed-biofilm reactor (FBR) was established to treat textile wastewater to evaluate the feasibility of replacing conventional treatment processes that involve activated sludge and coagulation units. A kinetic model was developed to describe the biodegradation of textile wastewater by FBR. Batch kinetic tests were performed to evaluate the biokinetic parameters that are used in the model. FBR column test was fed with a mean COD of 692 mg/L of textile wastewater from flow equalization unit. The influent flow rate was maintained at 48.4 L/h for FBR column test. Experimental data and model-predicted data for substrate effluent concentration (as COD), concentration of suspended biomass in effluent and the amount of carbon dioxide (CO(2)) produced in the effluent agree closely with each other. Microscopic observations demonstrated that the biofilm exhibited a uniform distribution on the surface of polyurethane foam sponge. Under a steady-state condition, the effluent COD from FBR was about 14.7 mg COD/L (0.0213 S(b0)), meeting the discharge standard (COD < 100 mg/L) that has been set by the government of Taiwan for textile wastewater effluent. The amount of biofilm and suspended biomass reached a maximal value in the steady state when the substrate flux reached a constant value and remained maximal. Approximately 33% of the substrate concentration (as COD) was converted to CO(2) during biodegradation in the FBR test. The experimental and modeling schemes proposed in this study could be employed to design a full-scale FBR to treat textile wastewater.

Nitrification/denitrification in swine wastewater using porous ceramic sticks with plastic rings as supporting media in two-stage fixed-biofilm reactors.

This study evaluated the performance of oxic-anoxic fixed-biofilm reactors (FBRs) using porous ceramic sticks with plastic rings as supporting media for nitrogen and organic carbon (as COD) removal from swine wastewater. Experimental results indicate that the removal efficiency of NH(4)(+)-N increased to 86-92% from 52-98% as the volumetric ammonium-nitrogen loading rate increased to 0.25 kg NH(4)(+)-N/m(3)-d from 0.082 kg NH(4)(+)-N/m(3)-d. Furthermore, during the denitrifying column test, the average removal efficiencies for COD and NO(x)-N were 83 and 76%, respectively. Only small amounts of NO(2)(-)-N and NO(3)(-)-N accumulated in the denitrifying FBR. The average values for NO(2)(-)-N and NO(3)(-)-N in effluent from denitrifying reactor were roughly 2 mg/L and 6 mg/L, respectively. Approximately 82% of NO(3)(-)-N was converted into N(2) by denitrifying bacteria in the denitrifying FBR. Approximately 98-100% high removal efficiencies of NO(x)-N could be reached in denitrifying FBR, when the ratio of COD(r)/NO(x)-N(r) was controlled at 9-12 throughout the test. Microscopic observations show that cell number on the ceramic sticks in denitrifying FBR was greater than that in nitrifying FBR in the final phase of colonization.

Perceived job stress and health complaints at a bank call center: comparison between inbound and outbound services.

This study investigated how perceived job stress and health status differ, as well as the relationships to inbound (incoming calls) versus outbound (outgoing calls) calling activities, for call center workers in a bank in Taiwan. The sample bank employed 289 call center workers at the time of the survey, ranging in age from 19 to 54 yr old. Data were obtained on individual factors, health complaints, perceived level job stress, and major job stressors. Overall, 33.5% of outbound operators and 27.1% of inbound operators reported frequently or always experiencing high stress at work, however, the differences between inbound and outbound operators were insignificant. "Having to deal with difficult customers" was the most frequent job stressor for all workers. Musculoskeletal discomfort, eye strain, and hoarse or sore throat were the most prevalent complaints among call center workers. The relationship between perceived job stress and health complaints indicated that workers who perceived higher job stress had significantly increased risk of multiple health problems, including eye strain, tinnitus, hoarse or sore throat, chronic cough with phlegm, chest tightness, irritable stomach or peptic ulcers, and musculoskeletal discomfort (with odds ratios ranging from 2.13 to 8.24). These analytical results suggest that perceived job stress in the call center profoundly affected worker health. This study identified main types of job stressors requiring further investigation.

Biodegradation of phenol with chromium(VI) reduction in an anaerobic fixed-biofilm process--kinetic model and reactor performance.

A mathematical model system was derived to describe the simultaneous removal of phenol biodegradation with chromium(VI) reduction in an anaerobic fixed-biofilm reactor. The model system incorporates diffusive mass transport and double Monod kinetics. The model was solved using a combination of the orthogonal collocation method and Gear's method. A laboratory-scale column reactor was employed to validate the kinetic model system. Batch kinetic tests were conducted independently to evaluate the biokinetic parameters used in the model simulation. The removal efficiencies of phenol and chromium(VI) in an anaerobic fixed-biofilm process were approximately 980 mg/g and 910 mg/g, respectively, under a steady-state condition. In the steady state, model-predicted biofilm thickness reached up to 350 microm and suspended cells in the effluent were 85 mg cell/l. The experimental results agree closely with the results of the model simulations.

Effects of using a screen filter on call center workers' visual fatigue measurement.

This study evaluated the potential effectiveness of screen filters in relieving visual fatigue. Critical flicker frequency (CFF), accommodation power, visual acuity, and subjective rating of visual fatigue were evaluated at four different stages: without screen filter, screen filter use of 2.5 mo., 5 mo., and 12 mo. For each stage, all measurements were taken before and after an 8-hr. workday. Analysis of variance was performed to test whether the screen filter use or measurement time had a significant effect on any of the visual fatigue measurements. The results indicated visual acuity was significantly improved after the use of a screen filter, while after the screen filter was installed, the CFF reading showed visual fatigue was more pronounced. Significant improvement in subjective ratings of double vision on screen was found after the screen filter use of 2.5 mo., but improvements disappeared after continuous use at 5 mo. A Hawthorne effect could have contributed to the short-term relief in visual fatigue and inconsistent findings in other visual performance measurements. Sorting out frequently used questions into a few definable areas and data sets might reduce the screen viewing time and visual fatigue more effectively.