The femur-tibia control system of stick insects--a model system for the study of the neural basis of joint control

In a form of top-down analysis, the femur-tibia control system of stick insects is investigated. Open-loop experiments show that it is mainly velocity-sensitive with an extremely low velocity-threshold, that it possesses a very high gain and that it has only a very small phase reserve and thus works close to instability. The closed-loop system generates catalepsy. The system consists of a single sense organ with approximately 80 sense cells with known characteristics, a small number of interneurones (mainly non-spiking ones) and a small number of motor neurones. The characteristics of the whole system can quantitatively be attributed to the characteristics of its elements. The gain of the loop is state-dependent and the system is 'switched off' during active movements and replaced by a control system with different attributes. It is discussed that most of the characteristics of this system are, at least qualitatively, similar to joint control systems in other animals. Because the described system can be more easily investigated than other systems (especially in vertebrates) it can serve as a model against which more complicated joint control loops may be compared.     

Pyridoxine for severe metabolic acidosis and seizures due to isoniazid overdose

A 15-year-old girl took 3 g of isoniazid (15 tablets) in a suicide attempt and was brought unconscious to the emergency room. She was in respiratory failure, with seizures that could not be stopped with diazepam. Severe metabolic acidosis with normal serum lactate developed (pH 6.85), but did not improve after infusion of bicarbonate. Intravenous administration of pyridoxine led to prompt cessation of the seizures and to gradual improvement of acid-base status. She recovered consciousness after several hours and was discharged a week later.     

THE INFLUENCE OF LOAD MISALIGNMENT DURING UNIAXIAL LOW-CYCLE FATIGUE TESTING—II: APPLICATIONS

Abstract— Models for predicting scatter bands due to bending have been applied to four alloys, namely AISI 316L, Nimonic 101, 9 Cr-1 Mo, and IN 718. The alloys were tested extensively by 26 laboratories in an international round robin exercise sponsored by the Community Bureau of Reference (BCR) of the EC. After initially selecting data for analysis on the basis of their confirmed conformance to the ASTM bending criterion, it has been shown that in all four materials a major fraction of the data scatter could be attributed to bending. Furthermore, at the lowest strain range the predicted bending component represents the highest proportion of the experimental interlaboratory scatter. Many laboratories did not report any measure of bending and so could not be used in the initial analysis. However, a further interesting deduction from the models is that the entire BCR data-set can be encompassed within a scatter band based upon a bending criterion that is twice the allowable ASTM limit. Differences in the extent of scatter between materials at a given total strain range can be attributed to the gradient of the logarithmic plot of total strain range as a function of lifetime.     

Melanocyte culture lines from Tyr-SV40E transgenic mice: models for the molecular genetic evolution of malignant melanoma

Transgenic Tyr-SV40E mice previously produced on the C57BL/6 inbred-strain background, with SV40 oncogenic sequences specifically expressed in pigment cells, are predisposed to melanoma [Bradl, M., Klein-Szanto, A., Porter, S. & Mintz, B. (1991). Proc. Natl. Acad. Sci. USA, 88, 164-168]. Separate lines of these animals differ genetically only in the number of copies and chromosomal site of integration of the transgene. Skin melanocytes from young mice with no apparent skin lesions were established in continuous culture from hemizygous donors with low, medium and high numbers of transgene copies, and from a homozygous offspring of the low-copy mouse line. The standard culture conditions enable C57BL/6 wild-type melanocytes to become stably immortalized without transformation. The transgenic cell lines all changed over time in an orderly progression. However, with greater numbers of transgene copies, the cells more rapidly displayed shorter doubling times, increased anchorage independence, reduced serum and growth factor requirements, decreased tyrosinase expression and melanin content, increased oncogene expression, and capacity to form malignant melanomas when tested by grafting. Melanocytes with the lowest number of transgene copies were of special interest. They grew more rapidly than the wild-type cells from the outset, but did not become tumorigenic until an apparently small number of still-unknown genetic changes had spontaneously occurred, or until the number of transgene copies was increased slightly by homozygosity. In contrast to the hemizygous low-copy cells, the homozygous counterparts underwent striking and rapid transformational changes and early conversion to malignancy. Thus such low-copy transgenic melanocyte lines afford an exceptional opportunity for molecular analysis of somatic genetic evolution toward malignant melanoma.     

IEEE-PES Transmission and Distribution Conference and Exposition Call for Papers

Static network-related system voltage stability margin (VSM) depends on the availability of reactive power to support the transport of real power from sources to sinks. Based on this premise, the total VAr loss is minimized in the unified OPF framework considering real and reactive power controllers, and its effect on VSM is studied. Studies are conducted on a three-bus system, the IEEE 30-bus system, and a 191-bus Indian electric power system, and their results are reported.     

BER performance analysis of a direct conversion receiver

Direct conversion receivers are increasingly popular for use in mobile terminals. This is due to advantages over other architectures such as heterodyne receivers in terms of cost, electrical current, and physical size. However, a direct conversion receiver often generates a DC-offset that has to be taken care of either by suppressing the DC-offset in the radio-frequency part of the receiver, or by taking care of it during baseband processing. A theoretical analysis of the bit error rate (BER) performance in a direct conversion receiver with different levels of DC-offset suppression is presented. Explicit results are presented on how the BER depends on the signal-to-noise ratio (SNR), the signal-to-DC-level, and the choice of pilot symbols both with M-QAM and M-PSK in a slow, flat Rayleigh fading channel. A design rule, which applies to the design of DC-compensation in direct conversion receivers, is also presented     

Photovaractor for remote optical control of microwave circuits

A photovaractor for the remote optical control of microwave circuits was studied. The photovaractor was fabricated as a p-i-n photodiode placed in a pigtailed fiber optical module. The study of the impedance in the frequency range up to 3 GHz in darkness and under illumination has shown that the photovaractor capacitance strongly depends on the incident optical power. The capacitance variation of the photovaractor diode under illumination is discussed     

Radiation-Chemical Behavior of TBP in Hydrocarbon and Chlorohydrocarbon Diluents under Conditions of Reprocessing of Spent Fuel from Nuclear Power Plants

Experiments were performed for comparative assessment of the effect of ionizing radiation on the service characteristics of 30% TBP solutions in various diluents: hexachlorobutadiene (HCBD), mixtures of n-paraffins (RED diluent), and fraction of naphthenic hydrocarbons (RZh diluent). The following main parameters were chosen for comparative assessment of the quality of irradiated extractant solutions: composition and behavior of diluent radiolysis products, effect of diluents on the TBP radiolysis, and aggregative stability of emulsions in the main operations of the extraction cycle. The service life of the extraction mixtures was estimated from variation of the above parameters with the irradiation dose. Principles for choosing solvents with increased service life under irradiation were substantiated.