Multiplexing intensity and frequency sensations for artificial touch by modulating temporal features of electrical pulse trains.

In neural prostheses, intensity modulation of a single channel (i.e., through a single stimulating electrode) has been achieved by increasing the magnitude or width of each stimulation pulse, which risks eliciting pain or paraesthesia; and by changing the stimulation rate, which leads to concurrent changes in perceived frequency. In this study, we sought to render a perception of tactile intensity and frequency independently, by means of temporal pulse train patterns of fixed magnitude, delivered non-invasively. Our psychophysical study exploits a previously discovered frequency coding mechanism, where the perceived frequency of stimulus pulses grouped into periodic bursts depends on the duration of the inter-burst interval, rather than the mean pulse rate or periodicity. When electrical stimulus pulses were organised into bursts, perceived intensity was influenced by the number of pulses within a burst, while perceived frequency was determined by the time between the end of one burst envelope and the start of the next. The perceived amplitude was modulated by 1.6× while perceived frequency was varied independently by 2× within the tested range (20-40 Hz). Thus, the sensation of intensity might be controlled independently from frequency through a single stimulation channel without having to vary the injected electrical current. This can form the basis for improving strategies in delivering more complex and natural sensations for prosthetic hand users.

[Removal of mixed waste gases by the biotrickling filter].

A biotrickling filter (BTF) was designed for treating mixed waste gases, which contained hydrogen sulfide (H2S), tetrahydrofuran (THF) and dichloromethane (DCM) at the start-up and steady states. The removal efficiency of H2S and DCM could maintain about 99% and 60%, respectively, and the removal efficiency of DCM was reduced from 90% to 37% with the shortening empty bed retention time (EBRT) form 50 to 20 seconds when the inlet concentrations were 200, 100, 100 mg x m(-3) of H2S, THF, DCM, respectively. In the theoretical study, the biodegradation efficiency of contaminants was H2S > THF > DCM by analyzing the Michaelis-Menten Dynamic model.

Biodegradation of tetrahydrofuran by Pseudomonas oleovorans DT4 immobilized in calcium alginate beads impregnated with activated carbon fiber: mass transfer effect and continuous treatment.

A novel entrapment matrix, calcium alginate (CA) coupled with activated carbon fiber (ACF), was prepared to immobilize Pseudomonas oleovorans DT4 for degrading tetrahydrofuran (THF). The addition of 1.5% ACF increased the adsorption capacity of the immobilized bead, thus resulting in an enhanced average removal rate of 30.3mg/(Lh). The synergism between adsorption and biodegradation was observed in the hybrid CA-ACF beads instead of in the system comprising CA beads and freely suspended ACF. The effective diffusion coefficient of the CA-ACF bead was not significantly affected by bead size, but the bead's value of 1.14×10(-6)cm(2)/s (for the bead diameter of 0.4 cm) was larger than that of the CA bead by almost one order of magnitude based on the intraparticle diffusion-reaction kinetics analysis. Continuous treatment of the THF-containing wastewater was succeeded by CA-ACF immobilized cells in a packed-bed reactor for 54 d with a >90% removal efficiency.

[Removal of hydrogen sulfide by plate type-biotrickling filter].

A plate type biotrickling filters (plate type-biotrickling filter, PTBTF) in which three layers are separately sprayed by nutrient solution of pH 2.5, 4.5 and 6.5, relatively, was designed for H2S removal at the start-up and steady states. The biofilm formation of PTBTF was completed within 14 d, and the removal efficiency of 100% was achieved at the inlet H2S concentration of 188.6 mg x m(-3). Afterwards, H2S removal efficiency remained above 99% with the inlet concentration between 100 mg x m(-3) and 1 000 mg x m(-3) and empty bed residence time (EBRT) between 28 s and 4 s. When removal efficiency was 90%, the maximum elimination capacity of PTBTF increased with EBRT (3.3-6 s), e. g. 1 019.0 g x (m3 x h)(-1) for EBRT 6 s. The elimination capacity of the upper, middle and lower layer varied with the inlet H2S loading. It was found that the microorganisms onto the packing carriers in upper, middle and lower layers increased significantly at the start-up state, and reached 1.29 x 10(7), 5.47 x 10(8), and 1.07 x 10(9) cells x g(-1), respectively, in 125 d by the means of fluorescence staining. The bacilliform and filamentous microorganisms were the dominants in the upper and lower layer, respectively, observed by scanning electron microscopy. The biological community analysis by denaturing gradient gel electrophoresis was also conducted in this study. The main products of SO4(2-) and sulfur were determined for H2S degradation.