Limited-trial Chase decoding

Chase decoders permit flexible use of reliability information in algebraic decoding algorithms for error-correcting block codes of Hamming distance d. The least complex version of the original Chase algorithms uses roughly d/2 trials of a conventional binary decoder, after which the best decoding result is selected as the final output. On certain channels, this approach achieves asymptotically the same performance as maximum-likelihood (ML) decoding. In this correspondence, the performance of Chase-like decoders with even less trials is studied. Most strikingly, it turns out that asymptotically optimal performance can be achieved by a version which uses only about d/4 trials.     

Electrical stimulation of the medial prefrontal cortex increases dopamine release in the striatum

Exogenous and endogenous glutamate has been shown to evoke dopamine (DA) release in the striatum using both in vitro and in vivo techniques. We hypothesized that stimulation of the prefrontal cortex (PFC) would phasically enhance striatal DA release via the glutamatergic corticostriatal pathway. To test this hypothesis, in vivo brain microdialysis was employed to measure extracellular concentrations of DA in the striatum during electrical stimulation of the PFC. Five rats were implanted with bilateral electrodes located in the medial PFC and dialysis probes in the dorsal striatum. Two days later the PFC of these awake, freely moving rats was stimulated first at 50 microA and then at 100 microA for 20 minutes at 2-hour intervals. Both currents significantly increased DA release. Extracellular DA rose rapidly during stimulation, peaked immediately afterward, and then slowly returned to baseline values. Dopamine reached 118% of baseline values with 50 microA stimulation and 138% with 100 microA stimulation. Histologic analysis using the fluorescent retrograde dye Fluoro Gold confirmed that cells projecting to the vicinity of the striatal dialysis probe originated in the vicinity of the PFC electrodes. These results provide direct evidence for phasic, excitatory modulation of striatal DA release by the PFC.     

The directional effects of passive eye movement on the directional visual responses of single units in the pigeon optic tectum

We have investigated the visual responses of 184 single units located in the superficial layers of the optic tectum (OT) of the decerebrate, paralysed pigeon. Visual responses were similar to those reported in non-decerebrate preparations; most units responded best to moving visual stimuli, 18% were directionally selective (they had a clear preference for a particular direction of visual stimulus movement), 76% were plane-selective (they responded to movement in either direction in a particular plane). However, we also found that a high proportion of units showed some sensitivity to the orientation of visual stimuli. We examined the effects of extraocular muscle (EOM) afferent signals, induced by passive eye movement (PEM), on the directional visual responses of units. Visual responses were most modified by particular directions of eye movement, although there was no unique relationship between the direction of visual stimulus movement to which an individual unit responded best and the direction of eye movement that caused the greatest modification of that visual response. The results show that EOM afferent signals, carrying information concerning the direction of eye movement, reach the superficial layers of the OT in the pigeon and there modify the visual responses of units in a manner that suggests some role for these signals in the processing of visual information.     

Retained fetal lung liquid in congenital lobar emphysema: a possible predictor of polyalveolar lobe

The purpose of this study was to determine whether retention of fetal lung liquid is more prevalent in polyalveolar congenital lobar emphysema than in conventional congenital lobar emphysema. Two patients with congenital lobar emphysema were prospectively identified in a 3-year period. Twenty-five such patients were identified in a retrospective study covering 39 years. Medical records were available for 22 patients who had 23 emphysematous lobes. Both babies from the prospective study and six subjects from the retrospective group had respiratory symptoms and underwent chest X-ray in the first day of life. Six of the eight babies with respiratory symptoms and chest imaging in the first day of life had retention of fetal lung liquid in an emphysematous lobe. All six of these lobes were polyalveolar. The lobe in one child was a polyalveolar lobe but without retained fetal lung liquid, and one child exhibited conventional lobar emphysema also without retained fetal lung liquid. One polyalveolar lobe caused no neonatal symptoms and was not imaged until the child was 3 months old. No baby with conventional lobar emphysema was shown to have retained fetal lung liquid. There seems to be a correlation between polyalveolar lobe and onset of respiratory symptoms in the first day of life. Retention of fetal lung liquid within the affected lobe was documented only in cases of polyalveolar lobe.     

Treatment of hypertension in nondiabetic renal disease

To clarify whether long-term impaired glucose tolerance (IGT) is associated with dysfunction of peripheral and autonomic nerves, age-matched men with IGT and diabetes mellitus were followed prospectively for 12-15 years, when peripheral and autonomic nerve function was assessed. The patients comprised four subgroups: (1) 51 IGT subjects (duration of IGT at least 12-15 years); (2) 35 diabetic patients, with IGT 12-15 years ago, who later developed diabetes; (3) 34 diabetic patients, duration of diabetes at least 12-15 years; and (4) 62 age-matched non-diabetic control subjects. Mean age of the whole study population was 61 +/- 2 years (mean +/- SD), not different in the four groups. Peripheral nerve function tests included nerve conduction velocities, amplitudes, distal latencies, F-reflexes, and sensory perception thresholds for heat, cold, and vibration. Autonomic nerve function tests included the heart rate reaction during deep breathing (expiration to inspiration ratio) and to tilt (acceleration and brake indices). Despite 12-15 years of IGT, peripheral nerve function did not differ between IGT and control subjects, whereas autonomic nerve function deviated; an abnormal expiration to inspiration ratio (a sign of vagal nerve dysfunction) was significantly more common (15/51 versus 5/62; p < 0.01) in IGT than in control subjects. Diabetic patients (groups 2 and 3) showed lower conduction velocities (in general 2-4 m s-1 lower) than IGT and control subjects in all tested nerves. In conclusion, diabetes but not IGT, is associated with peripheral nerve dysfunction.     

Dynamic Complexity Theory Revisited

Dynamic complexity investigates the required effort to maintain knowledge about a property of a structure under changing operations. This article introduces a refined notion of dynamic problems which takes the initial structure into account. It develops the basic structural complexity notions accordingly. It also shows that the dynamic version of the LOGCFL-complete problem D₂LREACH(acyclic) can be maintained with first-order updates.     

Limits of the output power in Er3+:ZBLAN singlemodefibre lasers

The saturation of the 2.71 μm laser output has been measured in erbium-doped ZBLAN singlemode fibres with Er³⁺ concentrations of 1000, 5000 and 10000 ppm mol. Limits of the single-mode-laser output are discussed