The adsorption of basic dye (Astrazon Blue FGRL) from aqueous solutions onto sepiolite, fly ash and apricot shell activated carbon: kinetic and equilibrium studies.

In this study, sepiolite, fly ash and apricot stone activated carbon (ASAC) were used as adsorbents for the investigation of the adsorption kinetics, isotherms and thermodynamic parameters of the basic dye (Astrazon Blue FGRL) from aqueous solutions at various concentrations (100-300 mg/L), adsorbent doses (3-12 g/L) and temperatures (303-323 K). The result showed that the adsorption capacity of the dye increased with increasing initial dye concentration, adsorbent dose and temperature. Three kinetic models, the pseudo-first-order, second-order, intraparticle diffusion, were used to predict the adsorption rate constants. The kinetics of adsorption of the basic dye followed pseudo-second-order kinetics. Equations were developed using the pseudo-second-order model which predicts the amount of the basic dye adsorbed at any contact time, initial dye concentration and adsorbent dose within the given range accurately. The adsorption equilibrium data obeyed Langmuir isotherm. The adsorption capacities (Q0) calculated from the Langmuir isotherm were 181.5 mg/g for ASAC, 155.5 mg/g for sepiolite and 128.2 mg/g for fly ash at 303 K. Thermodynamical parameters were also evaluated for the dye-adsorbent systems and revealed that the adsorption process was endothermic in nature.

A novel filter bank for biotelemetry.

In a multichannel biotelemetry system, signals taken from a patient are distributed along the available frequency range (bandwidth) of the system through frequency-division-multiplexing, and combined into a single composite signal. Biological signals that are limited to low frequencies (below 10 Hz) modulate the frequencies of respective sub-carriers. Other biological signals are carried in amplitude-modulated forms. It is recognized that recovering original signals from a composite signal at the receiver side is a technical challenge when a telemetry system with narrow bandwidth capacity is used, since such a system leaves little frequency spacing between information channels. A filter bank is therefore utilized for recovering biological signals that are transmitted. The filter bank contains filter units comprising switched-capacitor filter integrated circuits. The filters have two distinct and opposing outputs (band-stop (notch) and band-pass). Since most biological signals are at low frequencies, and modulated signals occupy a narrow band around the carrier, notch filters can be used to efficiently stop signals in the narrow frequency range. Once the interim channels are removed, other channels become well separated from each other, and band-pass filters can select them. In the proposed system, efficient filtering of closely packed channels is achieved, with low interference, from neighboring channels. The filter bank is applied to a system that carries four biological signals and a battery status indicator signal. Experimental results reinforce theoretical predictions that the filter bank successfully de-multiplexes closely packed information channels with low crosstalk between them. It is concluded that the proposed filter bank allows utilization of cost-effective multichannel biotelemetry systems that are designed around commercial audio devices, and that it can be readily adapted to a broad range of physiological recording requirements.

A versatile multichannel biotelemetry system.

A radiotelemetry system is introduced for analyzing several physiological parameters from free ranging patients within a transmission range of 100 metres. The parameters considered are two independent electromyograms, an electrocardiogram, and a body position indicator. A battery status signal is also transmitted. An equalizer network is utilized to improve the overall frequency response of the system. The composite signal from the equalizer can be recorded by using a tape recorder and demulitiplexed simultaneously. A filter bank is used for demultiplexing. Each filter unit in the bank provides outputs that emphasize and at the same time suppress signals in the same frequency range. The suppressed output supplies the signal to proceeding stages. Hence, an efficient filtering of closely packed multiplexed signals is achieved. The incoming original signals are recovered at outputs of demodulators following the filter bank. The proposed system provides an efficient and cost-effective way of physiological signal detection and storage from free-ranging patients. It is designed using commonly available electronic components. It can be implemented easily, and adapted to other physiological and physical parameters of interest.

Long-term ambulatory physiological surveillance equiment (LAPSE).

A system is described for the acquisition of physiological data for up to 24-hour periods in the ambulant subject free to undertake his usual daily activities. ECG and trunk acceleration signals are recorded on a small analogue magnetic tape recorder along with a stable time-reference. The standard C120 tape cassette used in the recorder is replayed at 60 times the recording speed and the recovered data automatically processed to yield outputs which describe the instantaneous heart rate response of the subject to particular activity. The system is evaluated and the potential indicated by examples of clinical application.