Steady Shift Research Articles

Management of keratoconus in Moorfields Eye Hospital

In a retrospective analysis of 88 new patients with a five year follow up who presented with keratoconus, contact lenses, particulary hard corneal lenses, provided the major contribution to the management of early and moderate keratoconus with an immediate improvement of up to 7 lines of Suellen visual acuity at diagnosis. Satisfactory contact lens tolerance has been achievedby improving wetting, stability and gas permeability factors, and with a steady shift towards the use of well tolerated contact lenses, visual acuity can be maintained at a satisfactory standard over several years. 88.6% of these eyes analysed retained a best acuity of 6/12 or better at five years. Moderate and severe complications of contact lens wear were rare although progressive loss of lens tolerance was a signifcant problem. Of those patients with severe keratoconus, 11.5% required penetrating keratoplasty. The results of this surgically managed group were good with 14 out of 20 eyes (70%) achieving a best corrected acuity of 6/6 or better and 19 (95%) achieving 6/12 or better.

Observation of a first-order structural phase transition in a monolayer of Pd on Nb(110) and its relationship to electronic structure

It is shown that a commensurate 1\ifmmode\times\else\texttimes\fi{}1 monolayer of Pd on a Nb(110) surface undergoes a first-order structural phase transition to an incommensurate monolayer Pd(111) structure when \ensuremath{\approx} 18% more Pd atoms are added to the surface. We find, however, that this phase transition has no substantial effect on the surface electronic structure. A steady shift toward the Fermi level of the local density of states at the surface is found as the Pd coverage is increased beyond about one monolayer. This shift correlates quite well with a previously observed increase in the hydrogen uptake rate.

Industrial Transformation and Occupational Change in the U.S., 1960-70

Increasingly, sociologists concerned with occupational mobility and the changes in the occupational distribution are turning their attention to the structural conditions for such changes. One important change has been industry shifts, particularly the decline of agriculture and the growth of services. In this paper we argue that industry shifts have an important effect on changes in the occupational structure. Using a shift-share approach, changes in the occupational structure of the U.S. between 1960 and 1970 are decomposed into an industry shift effect, an occupational composition effect, and an interaction effect. These effects vary for major occupational categories, but for total U.S. employment the industry shift effect accounted for about two-thirds of the change in occupational structure, the composition effect for one-third, and the interaction effect was negligible. It is not likely that there will be as important shifts in the industry structure during the next 30 years as in the last 30 years. But it has been the industry shifts that have mostly contributed to an expansion of the higher status occupations, particularly professionals and managers. Therefore, unless the occupational composition changes in such a way as to compensate for the diminishing effects of the industry structure, structural opportunities will either remain at current levels or even decline in the years to come. The present century has witnessed a sweeping transformation of the American labor force. This transformation entails fundamental changes in the allocation of workers to industries and in the type of work they perform. Many of these changes are familiar, based on the steady shift from an agriculturally oriented economy to one based on manufacturing. Less familiar, but equally impressive, is the rapid expansion of social, business, and financial services during the past decades. These services combined now employ close to one-third of all workers. The corresponding changes in the occupational structure of the U.S. labor force include the continuous shift ? 1980 The University of North Carolina Press. 0037-77321801010246-64$01.90

The effects of substituents upon the ultraviolet spectra of conjugated dienes : The applicability of woodward's rules

Data on the electronic spectra of conjugated dienes di-substituted with saturated hydrocarbon chains of increasing length have been collected from the literature. One aspect of these spectra, the fact that the absorption maximum for a cis-cis compound lies at longer wavelengths than that for the corresponding trans-trans, has received some attention in the literature, but no quantitative explanation of the observation has been offered. A second fact, that increasing substituent chainlength results in a steady shift of the absorption maxima to long-wavelength limits of ~235nm for cis-cis, ~233nm for cis-trans and trans-cis and ~ 231 for trans-trans, appears to have gone unremarked in spite of the fact that, as a result. Woodward's rules are not obeyed by such compounds. Quantitative interpretations of both these phenomena are described.

Electrical activation of visual pathways substitutes for tonic light input in triggering EEG correlates of food reward during conditioned behavior in cats

Cats trained to press a lever for 1 cc of milk reward normally show during the consummatory response high voltage 6--8 c/sec EEG synchronization associated with epicortical positive steady potential shift over the primary and secondary visual projections. The emergence of this postreinforcement synchronization (PRS) and Reward Contingent Positive Variation (RCPV) is known to depend upon appropriate gustatory input and presence of ambient light, although visual perception of reward and/or environment is not essential as shown in cats wearing translucent "milky" contact lenses. Training the animals in a paradigm in which a "light-off" cue signaled the availability of reward, and thus assigned positively reinforcing quality to the dark condition, also failed to restore the PRS-RCPV phenomenon in the absence of light. However, brief electrical stimuli applied to either the optic tract or the lateral geniculate nucleus substituted for unpatterned light input and fully restored the PRS-RCPV in the dark. The suprathreshold stimuli were effective only during the consummatory response. Maximum effect could be produced during a brief time period between 0.8 and 1.5 sec after the onset of consummatory response as judged by lapping activity, thus showing the specificity of the effect of visual input. Even during a relaxed wakefulness after satiation or during slow wave sleep or REM sleep the same electric stimuli were ineffective although they produced well-developed evoked potentials with all characteristic wave components. The results indicate that brain pathways utilize unpatterned i.e. noisy visual input in complex integrative processes involving gustatory input.

Dependence of reward contingent positive variation (RCPV) and cortical synchronization on visual input in the cat

Cats trained to press a lever for milk reward display high amplitude low frequency electrocorticographic post-reinforcement synchronization (PRS) associated with epicortical steady potential shift, termed Reward Contingent Positive Variation (RCPV), over the parieto-occipital cortex. Previously, it was found that the PRS-RCPV phenomenon depends on unpatterned light input devoid of any conceivable information or conditional property. Although training in the dark most likely eliminated the “novelty” factor and the resulting orienting reaction to “light off” as a cause of PRS-RCPV suppression, a possibility could not be excluded that the absence of ligh had a negatively reinforcing property preventing the emergence of PRS-RCPV. Hence, in the present study an experimental paradigm was used in which “light off” and/or “tone on” cues signalled the availability of reward, the “light off” periods extending through the consummatory response. Seven out of 9 cats, despite 2–4 months of daily training, and 85% correct timing of bar press performance, never showed a PRS-RCPV response (one animal showed only sporadic and poorly developed patterns). However, when the light was turned on during consumption, in 85% of such tests a fully developed PRS-RCPV emerged in a stimulus-bound manner. One animal was an exception and showed PRS-RCPV both in the absence and presence of light. It was concluded that light input plays a crucial role in the emergence of the PRS-RCPV phenomenon and therefore also participates in the integration of gustatory input.

Dose-dependent dual effect of morphine on electrophysiologic correlates of positive reinforcement (Reward Contingent Positive Variation: RCPV) in the cat

In cats trained to press a lever for milk reward, the postreinforcement EEG synchronization (PRS) and the associated epicortical steady potential shift, known as “Reward Contingent Positive Variation (RCPV) restricted to the occipital cortex, were studied prior to and after administration of morphine sulfate. Contrary to what has ordinarily been described as a typical feline response to morphine, such as restlessness, aggressiveness, rage, and exaggerated startle reaction to environmental stimuli, associated with an increased tonus of the brainstem-hypothalamic arousal system and desynchronized EEG patterns, doses of 0.1–0.4 mg/kg, IM, caused a strong monophasic enhancement of the PRS-RCPV phenomenon. Doses of 0.6–1.0 mg/kg, IM, had clearly a biphasic action: the initial enhancement of the PRS-RCPV responses was followed by their strong suppression. Chlorpromazine (0.1–1.6 mg/kg, i.e.) promptly restored the EEG responses. During the peak effect of the enhancing doses of morphine, the reward-related EEG phenomena also occurred prior to or after the nonrewarded bar press when the animals licked the empty cup. This dissociation of the PRS-RCPV from consumption was much more conspicuous in animals whose control frequency of the PRS oscillations was higher, and after morphine showed more significant slowing. Despite the strong facilitation of the PRS-RCPV in the presence of light, morphine, in contrast to LSD-25, was not able to restore the reward-induced phenomena in the dark.

Dissociation of cortical steady potential shifts from mass action potentials in cats awaiting food rewards

Cortical steady potential shift (SPS) and mass unit activity, derived from the same transcortical hybrid electrodes, were recorded in cats undergoing single alternation (SA) training. A 10-sec tone CS, occurring every 2 min, was alternately nonreinforced (N) and reinforced (R) with an intraoral food US. Results revealed: (1) Acquisition of a recurrent SPS pattern consisting of a gradual 200-300 micro V shift during the pre-R (N to R) interval followed by post-R shifting of opposite polarity during the R-to-N interval. (2) The pre-R SPS became dissociated from the integrated multiple unit (IMU) measure, but the post-R SPS remained associated with the IMU. (3) The CS elicited a conditional IMU response (cortical CR) when it signaled the US (R trial) but not when it signaled no US (N trial). The SPS pattern may reflect context-conditioned “expectancy”states (not detectable in IMU recording) postulated to “gate”the IMU CR on and off alternately.

A CNV-like negative shift in deep coma

In order to elucidate the unsolved problem of the genesis and “contingency” of the CNV, which is largely related to attention, expectancy and other attentive activities, two patients in deep coma were stimulated by means of repeated sets of paired stimuli (click, S 1, and flash, S 2, 900 msec later). The recorded responses were analysed according to the method generally applied for the detection of CNV in normal subjects. The standard EEG, eye movements and steady potential shift from the vertex, using the left mastoid as reference, were recorded. Relevant negative shifts between S 1 and S 2 were recorded from the vertex only after a great number of paired stimuli (120 and 150, respectively). Control experiments proved that artifacts and extracerebral potentials were not involved in eliciting this phenomenon. The slow negative potentials recorded did not differ morphologically from CNV in normal subjects but only in the number of paired stimuli required for their appearance.

Bromocresol Purple and Ethyl Red as Indicators of Events Linked to Changes in the Energization of Chloroplast Membranes

Abstract 1. Two dyes, bromocresol purple and ethyl red, were tested for their ability to register solution and membrane changes resulting from the illumination of suspensions of isolated chloroplasts. 2. Bromocresol purple can measure the external (suspension) pH both rapidly and accurately if the following precautions are observed: (a) since bromocresol purple stimulates electron flow to oxygen, either low concentrations (≤ 2 µm) of bromocresol purple or conditions for noncyclic electron transport must be used; (b) the absorbance shifts must be converted by formula to yield changes in proton concentration. 3. The disappearance of protons from the medium when the light is turned on is bi-exponential with half-times of about 0.7 s and 8 s. The release of protons into the medium when the light is turned off is exponential with a decay half-time of about 30 s. 4. A brief initial lag (l0.2 s) in the uptake of protons follows the onset of illumination, and there is a lag of up to 1 s in the release of protons at the end of illumination. These data suggest the presence of an intermediate pool between electron flow and proton movement. 5. One of the major components of the ethyl red response in buffered suspensions is a band shift, which is thought to represent a change in the position of ethyl red within the membrane resulting from illumination. These responses seem related to the state of coupling of the photosynthetic membrane and could serve as a sensitive indicator thereof. 6. The time relationship between ethyl red and bromocresol purple responses shows that changes in the membrane (ethyl red response) continue after the establishment of the steady state pH shift in the light. 7. Bromocresol purple and ethyl red offer promise as investigative tools for events linked to energy transduction in thylakoids.

Lysergic acid diethylamide (LSD-25) mimicks the effect of diffuse light input on EEG correlates of conditioned operant behavior in cats

Cats deprived of food and trained to press a lever for a milk reward, displayed postreinforcement EEG synchronization (PRS) associated with epicortical steady potential shift, i.e., “reward contingent positive variation” (RCPV) over the striate and parastriate cortex. Both phenomena depend on the input of diffuse light, even in subjects trained to perform in darkness. LSD-25 (15–30 μg/kg, im) restored the PRS-RCPV phenomena in total darkness. Pentobarbital (0.8–1 mg/kg, im) was ineffective although it significantly enhanced the PRS-RCPV responses in the presence of light. Some animals were more sensitive than others to LSD-25, and after administration of 20–30 μg/kg intramuscularly, showed dissociation between the EEG patterns and rewarded lever-pressing performance, which was particularly striking in the presence of ambient light.

Induction of sleep and “reward contingent positive variation” by photic stimuli in the cat

Cats trained, in the presence of light, to press a lever for milk reward displayed postreinforcement EEG synchronization (PRS) associated with epicortical steady potential shift (reward contingent positive variation). These phenomena, which occur over visual projections, have been previously interpreted as correlates of an active process of internal inhibition. Hence, an attempt was made to reinforce these processes by driving cortical activity using light flashes at a frequency of spontaneous PRS oscillations. The topographical distribution and amplitude of the epicortical steady potentials induced by flash-driven EEG synchrony were indistinguishable from spontaneous responses both during operant behavior and onset of sleep. The flash-driven responses had a significant hypnogenic effect, thus, corroborating the hypothesis that PRS reflects internal inhibitory processes.

Diffuse light input and quality of reward determine the occurrence of ‘Reward Contingent Positive Variation’ (RCPV) in cat

The effect of unpatterned light input on ECoG patterns and epicortical steady potentials were investigated in cats trained to press a lever for 0.8–1.0 ml of milk reward. High voltage (120–200 μV) bursts of post-reinforcement synchronization (PRS) with an average frequency of 7.8 c/sec were associated with epicortical positive steady potential shift, termed ‘Reward Contingent Positive Variation’ (RCPV). These ECoG phenomena occured over the striate, parastriate, and association cortex, and only in the presence of light in the test chamber, even though the subjects were trained in the absence of light. Visual perception of reward was not essential for the occurrence of PRS-RCPV phenomena, since they were observed in the same subjects whose patterned vision was totally prevented by translucent contact lenses or goggles. The role of diffuse light input (devoid of any conceivable conditional properties) in synaptic mechanisms of ECoG synchronization has been discussed. It is suggested that during instrumentally conditioned behavior, in constrast to a relaxed state and sleep onset, diffuse light input is necessary for triggering the intracortical phasing mechanism of neuronal activity which is presumably based on widespread and synchronized recurrent hyperpolarizing inhibition of large population on neurons. If this interpretation is correct, the epicortical RCPV can be visualized as resulting from electrotonic spread of the hyperpolarization of neuronal soma to apical dendrites. Since the PRS-RCPV responses are not restricted to striate and parastriate cortex in alert subjects 7,25–27, it is postulated that diffuse light input supplies the ‘electromotive energy’ for inhibitory mechanisms in cortical regions involved in processing of both visual and non-visual input.

Cholinergic mechanism determines the occurrence of Reward Contingent Positive Variation (RCPV) in cat

The effects of anticholinergic drugs (atropine and scopolamine) and an cholinesterase inhibitor, physostigmine were studied with regard to their action on post-reinforcement EEG synchronization (PRS) and associated epicortical steady potential shift (Reward Contingent Positive Variation; RCPV) in cats trained to press a lever for milk reward.

Studies of exophthalmic goitre—V: The course of mortality in Canada, 1921–1965 and its significance

The course of mortality from exophthalmic goitre in 6 provinces of Canada has been reviewed. There was a marked increase in each province in 1924 or shortly thereafter. This continued for twenty or thirty years and was accompanied by a steady shift to greater and greater age of death. The order of mortality in cohorts of 5 or 10 yr difference in age continued the same from the period of the first marked increase in mortality for 30 or 40 yr or until the age of 70–79. The ages at which the women died are consistent with the view that nearly all had acquired the disease between 1924 and 1929, or earlier. It is believed that these facts support the view expressed by Meulengracht in 1949 that exophthalmic goitre might be caused by a “specific infectious agent of unknown nature” [13]. This agent might have been brought to Canada by military personnel in returning from Europe in 1919 or it might be related to the pandemic of influenza in 1917–1918, or it might not be related to either occurrence. It is proposed to obtain statistics from countries not directly involved in the war of 1914–1918 in order to test the first of these hypotheses.

Instrumental conditioning of the rat cardiac control systems.

The PR, PP, and RR intervals of the rat EKG were instrumentally conditioned using a variety of reinforcement schedules under computer control. The PR and PP intervals could be conditioned independently. Individual rats demonstrated either a steady shift of their response distribution or an abrupt change of an all-or-none variety. Some response distributions shifted continuously; others, through the growth of new response patterns in a manner reminiscent of hypothesis-testing behavior of human subjects. A study of the effects of single reinforcements showed that each reinforcement contributed to the learning behavior of the subject, in a well-defined but nonlinear fashion.

The effects of hypoxia on certain aspects of visual performance.

Accommodation, convergence, and stereoacuity were measured in 19 aviators at sea level and at altitudes to 18,000 feet. Most subjects showed a decrement of all three skills, while none improved. Hypoxia has a detrimental effect on these functions, but there is considerable variation in tolerance to oxygen deprivation. No change was observed in phorias or in plus acceptance at near. A small but steady shift toward myopia was observed with increased altitude.

The Aftereffects of Annexation - A Case Study

Because of the post World War II population growth, the steady shift of our country’s people from rural areas to urban centers, and seemingly irreversible agonies of congestion, urban sprawl and deterioration, responsible City Governments are obliged to exercise whatever means are available to them to protect the quality of their immediate environment as well as to secure material for orderly future growth, additional land area. In very few cases has State Government proven itself able and free to remedy problems of uncontrolled urban growth once they exist. Accordingly, the City must be its own defender. Where state law does not provide the municipality with controls for zoning and development of abutting lands about its periphery, annexation is one positive means for acquiring necessary protective authority. This case history deals with political, financial, legal, inter-jurisdictional, urban planning, and other problems which confronted Oklahoma City in its successful effort to protect its future and the future of its service commitments.

RADIATIVE LIFETIMES IN n-TYPE GALLIUM ARSENIDE

Radiative lifetimes and time-resolved spectra have been obtained for high-purity n-type gallium arsenide at low temperatures. The ∼ 1.51-eV bands, generally associated with the annihilation of free and bound excitons, decay very rapidly, τ < 15 nsec. The 1.49-eV band, variously described as donor-acceptor recombination or as a free-to-bound recombination, has a longer nonexponential decay. For this band, the time-resolved spectra show a steady shift to lower energy as the delay after the pulse is lengthened. The conclusion drawn is, that the 1.49-eV band arises from a D-A recombination process.

Steady potential correlates of positive reinforcement: reward contingent positive variation.

A positive reinforcement with food produced high-voltage bursts of alpha activity over the posterior marginal gyrus in a cat deprived of food and water. This synchronization was always associated with a large (180 to 300 microvolt), positive steady potential shift comparable to that occurring during the onset of sleep. Since this shift was contingent upon the relative appropriateness and desirability of food reward, it was termed reward contingent positive variation.