Relay Unit Research Articles

Integration of Layered Redox Proteins and Conductive Supports for Bioelectronic Applications.

Integration of redox enzymes with an electrode support and formation of an electrical contact between the biocatalysts and the electrode is the fundamental subject of bioelectronics and optobioelectronics. This review addresses the recent advances and the scientific progress in electrically contacted, layered enzyme electrodes, and discusses the future applications of the systems in various bioelectronic devices, for example, amperometric biosensors, sensoric arrays, logic gates, and optical memories. This review presents the methods for the immobilization of redox enzymes on electrodes and discusses the covalent linkage of proteins, the use of supramolecular affinity complexes, and the reconstitution of apo-redox enzymes for the nanoengineering of electrodes with protein monolayers of electrodes with protein monolayers and multilayers. Electrical contact in the layered enzyme electrode is achieved by the application of diffusional electron mediators, such as ferrocene derivatives, ferricyanide, quinones, and bipyridinium salts. Covalent tethering of electron relay units to layered enzyme electrodes, the cross-linking of affinity complexes formed between redox proteins and electrodes functionalized with relay-cofactor units, or surface reconstitution of apo-enzymes on relay-cofactor-functionalized electrodes yield bioelectrocatalytic electrodes. The application of the functionalized electrodes as biosensor devices is addressed and further application of electrically "wired" enzymes as catalytic interfaces in biofuel cells is discussed. The organization of sensor arrays, self-calibrated biosensors, or gated bioelectronic devices requires the microstructuring of biomaterials on solid supports in the form of ordered micro-patterns. For example, light-sensitive layers composed of azides, benzophenone, or diazine derivatives associated with solid supports can be irradiated through masks to enable the patterned covalent linkage of biomaterials to surfaces. Alternatively, patterning of biomaterials can be accomplished by noncovalent interactions (such as in affinity complexes between avidin and a photolabeled biotin, or between an antibody and a photoisomerizable antigen layer) to provide a means of organizing protein microstructures on surfaces. The organization of patterned hydrophilic/hydrophobic domains on surfaces, by using photolithography, stamping, or micromachining methods, allows the selective patterning of surfaces by hydrophobic, noncovalent interactions. Photoactivated layered enzyme electrodes act as light-switchable optobioelectronic systems for the amperometric transduction of recorded photonic information. These systems can act as optical memories, biomolecular amplifiers, or logic gates. The photoswitchable enzyme electrodes are generated by the tethering of photoisomerizable groups to the protein, the reconstitution of apo-enzymes with semisynthetic photoisomerizable cofactor units, or the coupling of photoisomerizable electron relay units.

Glucose oxidase electrodes via reconstitution of the apo-enzyme: tailoring of novel glucose biosensors

Reconstitution of an apo-flavoenzyme with a relay-FAD-cofactor dyad yields an electrically contacted enzyme, “electroenzyme”. This is exemplified by the reconstitution of apo-glucose oxidase, apo-GOx, with a ferrocene–tethered FAD-cofactor. The resulting semisynthetic protein stimulates the bioelectrocatalyzed oxidation of glucose. Kinetic analysis of the ferrocene–FAD reconstituted enzyme reveals that its electrical communication with an electrode support is superior as compared to a protein randomly functionalized by ferrocene relay units. A pyrroloquinolinoquinone (PQQ)–FAD cofactor monolayer is assembled on a Au-electrode. Apo-GOx is reconstituted on the solid support to yield an aligned enzyme electrode of unprecendently efficient electrical contact. The electron-transfer turnover rate with the electrode is estimated to be 900±150 s −1, a value close to the electron transfer rate between native GOx and molecular oxygen. The effective electrical communication of the integrated enzyme electrode stimulates the efficient bioelectrocatalyzed oxidation of glucose, and results in high current densities and high sensitivity for glucose. The effective electrical contact of the enzyme-electrode yields also a specific glucose sensing electrode that is not perturbed by oxygen or interferrants. The possible application of the enzyme-electrode as an invasive biosensor is addressed.

Time-Resolved Fluorescence of Ferrocene/Flavin/Viologen/TCNQ Hetero LB Film

Time-resolved fluorescence was measured with hetero Langmuir-Blodgett (LB) films consisting of ferrocene/flavin/viologen/TCNQ on quartz substrate. Ferrocene, flavin, viologen and TCNQ were used as a electron donor (D), sensitizer (S), relay (R) and acceptor (A) units, respectively. Power dependence on charge separation rate was investigated to examine the local heating problem or the excited state annihilation. Based on the decay of fluorescence, charge separation from excited S to R (or A) was calculated. Result showed that long-range electron transfer from S to A occurred in the D/S/R/A hetero LB film in addition to the electron transfer from S to R.

ChemInform Abstract: Ruthenium‐Catalyzed Polycyclization Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Ruthenium-Catalyzed Polycyclization Reactions

The application of ruthenium alkylidenes such as 1 to the catalysis of polycyclization reactions is reported. Several acyclic precursors have been synthesized and reacted with 1. These precursors vary in topology and contain acetylenic and/or cycloolefinic metathesis relays. The cyclization reactions proceed in moderate to good yields to produce polycyclic polyenes when the precursors are subjected to catalytic amounts of 1. In general, precursors bearing n relay units generate polycycles containing (n + 1) rings.

Improving enzyme-electrode contacts by redox modification of cofactors.

Efficient electron transfer of redox proteins to and from their environment is essential for the use of such proteins in biotechnological applications such as amperometric biosensors and photosynthetic biocatalysts. But most redox enzymes lack pathways that can transport an electron from their embedded redox site to an electrode or a diffusing photoexcited species. Electrical communication between redox proteins and electrode surfaces has been improved by aligning proteins on chemically modified electrodes, by attaching electron-transporting groups and by immobilizing proteins in polymer matrices tethered by redox groups. Generally these methods involve contacting the enzymes at random with electron relay units. Here we report an approach that allows site-specific positioning of electron-mediating units in redox proteins. We strip glucose oxidase of its flavin adenine dinucleotide (FAD) cofactors, modify the latter with redox-active ferrocene-containing groups, and then reconstitute the apoprotein with these modified cofactors. In this way, electrical contact between an electrode and the resulting enzyme in solution is greatly enhanced in a controlled and reproducible way.

Taste responses in neurons in the nucleus of the solitary tract that do and do not project to the parabrachial pons.

1. Mechanisms of neural coding of gustatory stimuli were studied in the nucleus of the solitary tract (NTS), the first relay in the neural pathway for gustation, in anesthetized rats. Taste-responsive NTS units were identified as "relay" or "nonrelay" based on the electrophysiological response to electrical pulses delivered to the parabrachial nucleus of the pons (PbN), the second relay in the neural pathway for gustation. Coding mechanisms in each group were analyzed separately. 2. Taste responses to sapid solutions of NaCl (0.1 M), HCl (0.01 M), quinine HCl (0.01 M), sucrose (0.5 M) and Na-saccharin (0.004 M) were recorded in single units in the NTS. After gustatory stimulation, electrophysiological responses to electrical stimulation of the taste-responsive part of the ipsilateral PbN were recorded. A 0.2-ms pulse was delivered at 75-250 microA at a rates of 1, 25, 50 and 100 pps through a bipolar stainless steel electrode. An antidromic response was defined as a time-locked spike that occurred at a fixed latency after PbN stimulation that followed high stimulation frequencies. A collision test also was performed. 3. Of 42 taste-responsive NTS units, 19 (45%) were relay units, 22 (52%) were nonrelay and 1 unit was activated orthodromically by PbN stimulation. Latencies of evoked spikes ranged from 1.75 to 4.0 ms 2.1 +/- 0.2 ms (mean +/- SE, median, 1.75 ms). 4. Examination of general response characteristics revealed few differences among relay and nonrelay units.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of Glutathione Reductase by Light: A Novel Approach to Design Redox Photo‐Enzymes

Light‐induced electron transfer within a protein, coupled with chemical transformations, was achieved with the glutathione reductase modified by eosin isothiocyanate. The dye functions both as an initiator for the electron transfer and as a relay unit in the protein backbone that facilitates the electrical communication with the redox center at which the oxidized glutathione is reduced.

First results with a new estuarine fish tracking system

A ‘sonar buoy’ tracking system has been developed at the MAFF Fisheries Laboratory based upon acoustic transmitting tags and relay units which retransmit the pulsed acoustic signal as a radio signal. The output from several such ‘sonar buoys’ is monitored by a single automatic recording station on the shore. The system has been used on salmon in the estuary of the River Fowey in Cornwall, providing useful data on the behaviour of returning adults before they enter the river. The tags also transmit a radio frequency signal to allow tracking in the river itself. Of fourteen fish tagged in 1985, six were recorded entering the river between 12 h and 41 days after being released. Another fish was recaptured in a coastal net 160 km to the east. These few preliminary results indicated two distinct patterns of behaviour: one fish remained in deep water in the lower estuary for several days, often lying near moored ships or jetties; at other times fish made extensive excursions up the estuary with the tide, usually returning with the ebb.

Development of custom LSIs for protective relays and their evolution to new static relays

A relay LSI and a filter LSI are developed for static distance relays. The relay LSI is based on the phase-comparison scheme and applicable to a reactance relay, a mho relay, an offset mho relay, and an ohm relay. Key technologies used to meet the relay requirements are CMOS switched-capacitor technologies. Circuit compositions and characteristic test results are described. A prototype relay unit demonstrated superiority to a conventional unit in terms of its compactness. High reliability (because of the small number of parts), high accuracy, and very low power dissipation. >

Coordination-Free Ground-Fault Detection for Mine Distribution Systems

A ground-fault relaying scheme is presented that is intended to eliminate the need for time-delay relays for ground-fault detection on mine electrical distribution systems. The concept is based on pilot-relaying logic, and existing ground-check and grounding conductors are used to convey ground-fault information between adjacent relay units. The new scheme should not add any additional work during the installation of mine power systems and should minimize the expertise needed for power-system operation. To illustrate this concept, the design and development of the new relaying system is presented. The performance of a prototype relay during laboratory simulations is also given. Although the work is projected at underground coal mining, the relay appears feasible for any extensive radial distribution system.

The use of the Hersch cell for the measurement of small oxygen concentrations in sealed electrical contact units

A modification to the Hersch cell is described which permits the measurement of oxygen concentrations in the gas phase of encapsulated electrical switches. Using this technique 1 ppm of oxygen can be detected in a reed relay unit of volume 0.1 cm3.

Skylab Multispectral Scanner (5-192)â€

In this paper we describe the design and performance of a Multispectral Scanner. The optical system of Skylab Multispectral Scanner (S-192) consists of an image plane scanner (telescope), a spectrometer for separation of the radiation into 13 spectral bands, and a 13-element (Hg,Cd)Te detector array. The image plane scanner is a new system based on three interrelated main features: (1) a reflective adaptation of the Schmidt principle; (2) a conical line scan in which all field elements are brought to and corrected on axis; and (3) a scanning arrangement in which the aperture stop of the system, located in a relay unit, is imaged at the center of curvature of the spherical primary mirror. Replacing the physical stop used in the classical Schmidt configuration with a virtual one makes the system much more compact. As a consequence of the image plane scanning and the Schmidt symmetry, the system scans at a large radial angle (11-degree diameter) and at an extremely high rate (6000 rpm) with relatively small scanning mirrors and a large entrance pupil diameter (43 cm). The spectrometer divides the radiation into 13 spectral bands, 12 of which are located between 0.4 and 2.35 micrometers and the other, 10.2-12.5 micrometers. A dichroic beamsplitter separates the far IR band from the 12 lower wavelength bands, which are dispersed by prisms. Photographic reproductions of the actual flight recordings show 80-meter resolution at an altitude of 440 km.

Data Processing System by Computer for GC/MS.

The full automatic system including data acquisition and processing for GC/MS was constructed, and its applicability was studied. The mass spectrometer(Hitachi RMU 6-E single-focusing)and a small computer(JEOL JEC-5)with 4 k words of 16-bit length and with a 2-channel 8-bit A-D converter were adopted. So as to scan successively and automatically, GC/MS was partially modified by introducing the meter relay units and a solenoid valve. The electric out-put of mass spectrometer is digitized at a rote of 4500 points per sec. while the spectrometer scans in the range m/e 0-600 in 5 sec., and the data are punched out immediately as a tape in a few sec. in order to save core memory. The computer reads the tape, calculates m/e values, normalizes the intensities, and prints out the mass spectra in digital form. M/e values were correct up to 300, and the pattern coefficient was quite similar to that of the visicorder, and these values were suitable for further processing such as searching the standard files of mass spectra. This system with automatic scanner enables us a full automatic data reduction for GC/MS method.

Stand for the testing and tuning of radioisotopic relay units (E)

Stand for the testing and tuning of radioisotopic relay units (E)

A Three-Year Study on the Effect of Fly Control on Milk Production by Selected and Randomized Dairy Herds 1

During the three consecutive summers of 1957, 1958, and 1959, 99 lactating cows were used to test the effect of fly control on milk production under varied farm conditions on three farms in Centre County and Northumberland County, Pa. On the University and Tilford farms, the animals were selected on the basis of milk production, stage of lactation, body weight, age, and general physical condition; these were divided into two similar groups, the treated and untreated, which were managed alike throughout the trials. On the X Farm, two randomized herds served as treated groups and a third one as the untreated control; no attempt was made to equalize the management of the three randomized herds. The flies on the three farms were the horn fly, Haematobia irritans (L.), the stable fly, Stomoxys calcitrans (L.), the horse flies, Tabanus sulcifrons (Maequart) and T. giganteus (DeGeer), the house fly, Musca domestica L., and the face fly, Musca autumnalis DeGeer. Treatments for fly control included the use of spray and aerosol formulations containing various combinations of such principal ingredients as methoxychlor, dimethoate, synergized pyrethrins, R-1207 (3-chloropropyl n-octyl sulfoxide), MGK R-326 (di- n -propyl isocinehomeronate), butoxy polypropylene glycol, diethyltolumide, and Thanite® (isobornyl thioeyanoacetate, 82%, other related terpenes, 18%). The formulations were applied by means of two automatic devices: an electric-eye-controlled sprayer consisting of a pipe system with 10 nozzles, a photoelectric relay unit, and a pump-motor assembly; and a automatic photoelectric aerosol applicator (also known as automatic photoelectric device) equipped with a triggering mechanism for releasing aerosol from containers. Cows were sprayed once daily after milking, as they passed through the doorways or chutes at which the devices were mounted. Milk production records were kept during the treatment period as well as the pretreatment and posttreatment periods, except on the Tilford Farm. These tests showed that under the conditions prevailing in this investigation, fly control did not have significant effect on milk production by the selected herds on the University and Tilford Farms, which were well managed and liberally supplied with supplementary feeds. This was consistently true throughout the three seasons regardless of the differences in the degree of fly infestation, ranging from heavy to light, or in the effectiveness of treatments, varying from excellent to unsatisfactory. It also appeared that neither the absorption of small amounts of methoxychlor by the treated cows nor repeated applications of oil-based sprays had adverse effect on milk productivity of the animals concerned. Of the six selected or randomized herds receiving spray or aerosol treatments, only one randomized herd on the X Farm showed favorable response; the average daily crease in milk production in this herd, which was poorly managed and supplied with very scanty pasture and limited supplements, was significantly less than that in the untreated control. Statistical analyses indicated that the decrease in milk production by the treated herd was approximately one-third that of the untreated. Findings of the 3-year study lead to the suggestion that among the factors involved in determining the effect of fly control on milk production, herd management with particular reference to the supply of pasture and supplements could play a dominant role.

Effectiveness of Aerosol Formulations Containing Methoxychlor and Other Insecticide-Repellents against Biting Flies on Cattle, and Analyses of Milk from Treated Animals1

Aerosol containers charged with 1, 2, and 4% of methoxyehlor in various combinations with N,N-diethyl- m -toluamide, Thanite® (isobornyl thiocyanoacetate-82%), MGK R-326 (di- m -propyl isocinchomeronate), pyrethrins, and other ingredients were released on lactating cows by means of an automatic photoelectric device. The major components of the device consisted of a rectangular-shaped wooden frame on which were mounted a photoelectric relay unit and a triggering mechanism. Three aerosol containers were strategically located on the frame. The aerosol spray was released instantly as cattle entered the frame and stopped as soon as they left. On the average, actual spraying time per animal was 1.5 seconds; 150 animals were treated by a set of three 12-ounce containers, a dosage of approximately 7 ml. being discharged on each animal. The spray was applied once daily. Milk from both treated and untreated cows Was collected and analyzed once or twice a week. Results of the tests made over a period of 14 weeks showed that the aerosol formulations gave consistently excellent control of the horn fly, Siphona irritans (L.), but. limited protection against the stable fly, Stomozys calcitrans (L.). None of the milk samples analyzed showed a detectable amount of methoxychlor. The current price for the parts of the automatic device was between 20 and 25, and the base cost of the containerws and aerosol ingredients averaged between 0.6 cent and 1 cent per animal per application.

Part II — Design and performance

THE INTRODUCTION of a 3-phase compensator concept affords an entirely new approach to distance relaying. This new scheme has been designed so that one relay provides protection against all phase faults for a single zone. Transient overreach of the sensing unit has been eliminated. A single type of basic relay unit is used to interpret the output of the static compensator network and the moving element in the relay unit has been designed for low contact bounce at both low and high energy levels.

Inverse-time underfrequency relay

THIS PAPER describes a magnetic inverse-time underfrequency relay unit. It contains a relay which is operated when the frequency of an aircraft alternator drops below 380 cps (cycles per second). The time required for the relay to pick up is an inverse function of how far the frequency is below 380 cps. The complete unit contains a frequency-sensitive circuit which provides a voltage signal proportional to alternator frequency for driving a magnetic amplifier which has a very long time constant. The output of the magnetic amplifier is the coil of the underfrequency relay.

Relay unit for time signal receiver

Relay unit for time signal receiver