Spatial frequency and the mediation of short-term visual storage.

The perceived duration of a photopically illuminated, fixated grating presented for 50 milliseconds increased (from 300 to 500 milliseconds) with spatial frequency (0.9 to 15 cycles per degree). This suggests a sustained neural channel contribution to short-term visual storage, and argues against a pure photoreceptor, especially a rod, locus for such storage.

A phantom-motion aftereffect.

Motion aftereffects, typically found to result only from localized retinal stimulation, were obtained within regions of the visual field that had not been stimulated by moving contours. "Phantom" stripes are seen moving through a physically homogeneous (empty) region of the visual field when vertical stripes move above and below that region. Immediately afterward, stationary stripes in the previously empty region appear to move in the opposite direction. This phantom-motion aftereffect provides a novel instance of the way global structure affects processes that have been assumed to be influenced only by simpler local spatial and temporal variables.

Infrared observations of the uranian system.

The infrared interferometer spectrometer (IRIS) on Voyager 2 recorded thermal emission spectra of Uranus between 200 and 400 cm(-1) and of Miranda and Ariel between 200 and 500 cm(-1) with a spectral resolution of 4.3 cm(-1). Reflected solar radiation was also measured with a single-channel radiometer sensitive in the visible and near infrared. By combining IRIS spectra with radio science results, a mole fraction for atmospheric helium of 0.15 +/- 0.05 (mass fraction, 0.26 +/- 0.08) is found. Vertical temperature profiles between 60 and 900 millibars were derived from average polar and equatorial spectra. Temperatures averaged over a layer between 400 to 900 millibars show nearly identical values at the poles and near the equator but are 1 or 2 degrees lower at mid-latitudes in both hemispheres. The cooler zone in the southern hemisphere appears darker in reflected sunlight than the adjacent areas. An upper limit for the effective temperature of Uranus is 59.4 kelvins. Temperatures of Miranda and Ariel at the subsolar point are 86 +/- 1 and 84 +/- 1 kelvins, respectively, implying Bond albedos of 0.24 +/- 0.06 and 0.31 +/- 0.06, respectively. Estimates of phase integrals suggest that these satellites have unusual surface microstructure.

Infrared observations of the saturnian system from voyager 2.

During the passage of Voyager 2 through the Saturn system, infrared spectral and radiometric data were obtained for Saturn, Titan, Enceladus, Tethys, Iapetus, and the rings. Combined Voyager 1 and Voyager 2 observations of temperatures in the upper troposphere of Saturn indicate a seasonal asymmetry between the northern and southern hemispheres, with superposed small-scale meridional gradients. Comparison of high spatial resolution data from the two hemispheres poleward of 60 degrees latitude suggests an approximate symmetry in the small-scale structure, consistent with the extension of a symmetric system of zonal jets into the polar regions. Longitudinal variations of 1 to 2 K are observed. Disk- averaged infrared spectra of Titan show little change over the 9-month interval between Voyager encounters. By combining Voyager 2 temperature measurements with ground-based geometric albedo determinations, phase integrals of 0.91 +/- 0.13 and 0.89 +/- 0.09 were derived for Tethys and Enceladus, respectively. The subsolar point temperature of dark material on Iapetus must exceed 110 K. Temperatures (and infrared optical depths) for the A and C rings and for the Cassini division are 69 +/- 1 K (0.40 +/- 0.05), 85 +/- 1 K (0.10 +/- 0.03), and 85 +/- 2 K (0.07 +/- 0.04), respectively.

Infrared observations of the jovian system from voyager 2.

Infrared spectra obtainedfrom Voyager 2 have provided additional data on the Jovian system, complementing those obtained from Voyager 1. The abundance ratio of ethane to acetylene in Jupiter's atmosphere appears to be about three times larger in the polar regions than at lower latitudes. A decidedly hemispherical asymmetry exists, with somewhat higher ratios prevailing in northern latitudes. An overall increase in the abundance ratio by a factor of about 1.7 appears to have occurred between the Voyager 1 and 2 encounters. Global brightness temperature maps of Jupiter at 226 and 602 cm(-1) exhibit a large amount of local- and planetary-scale structure, as well as temporal variability. Although heterogeneous cloud structure and ammonia concentration in the lower troposphere may contribute to the appearance of the 226-cm(-1) map, the detail in the 602-cm(-1) maps probably represents the actual horizontal thermal structure near the tropopause and suggests that dynamical heating and cooling processes are important. Low-latitude surface temperatures on the Galilean satellites rangefrom approximately 80 K on the dark sides to 155 K at the subsolar point on Callisto. Below a thin insulating layer, the thermal inertia of Callisto is somewhat greater than that of Earth's moon. Upper limits on the infrared optical depth of the Jovian ring rangingfrom approximately 3 x 10(-4) at 250 cm(-1) to 3 x 10(-3) at 600 cm(-1) have been found.

Infrared observations of the jovian system from voyager 1.

The infrared spectroscopy and radiometry investigation has obtained spectra of Jupiter and its satellites between approximately 180 and 2500 cm(-1) with a spectral resolution of 4.3 cm(-1). The Jupiter spectra show clear evidence of H(2), CH(4) C(2)H(2), C(2)H(6), CH(3)D, NH(3), PH(3), H(2)O, and GeH(4). A helium concentration of 0.11 +/- 0.03 by volume is obtained. Meridional temperature cross sections show considerable structure. At high latitudes, the stratosphere is warmer in the north than in the south. The upper troposphere and lower stratosphere are locally cold over the Great Red Spot. Amalthea is warmer than expected. Considerable thermal structure is observed on Io, including a relatively hot region in the vicinity of a volcanic feature.

Infrared observations of the saturnian system from voyager 1.

During the passage of Voyager 1 through the Saturn system, the infrared instrument acquired spectral and radiometric data on Saturn, the rings, and Titan and other satellites. Infrared spectra of Saturn indicate the presence of H(2), CH(4), NH(3), PH(3), C(2)H(2), C(2)H(6), and possibly C(3)H(4) and C(3)H(8). A hydrogen mole fraction of 0.94 is inferred with an uncertainty of a few percent, implying a depletion of helium in the atmosphere of Saturn relative to that of Jupiter. The atmospheric thermal structure of Saturn shows hemisphere asymmetries that are consistent with a response to the seasonally varying insolation. Extensive small-scale latitudinal structure is also observed. On Titan, positive identifications of infrared spectral features are made for CH(4), C(2)H(2), C(2)H(4), C(2)H(6), and HCN; tentative identifications are made for C(3)H(4) and C(3)H(8). The infrared continuum opacity on Titan appears to be quite small between 500 and 600 cm(-1), implying that the solid surface is a major contributor to the observed emission over this spectral range; between 500 and 200 cm(-1) theopacity increases with decreasing wave number, attaining an optical thickness in excess of 2 at 200 cm(-1). Temperatures near the 1-millibar level are independent of longitude and local time but show a decrease of approximately 20 K between the equator and north pole, which suggests a seasonally dependent cyclostrophic zonal flow in the stratosphere of approximately 100 meters per second. Measurements of the C ring of Saturn yield a temperature of 85 +/- 1 K and an infrared optical depth of 0.09 +/- 0.01. Radiometer observations of sunlight transmitted through the ring system indicate an optical depth of 10(-1.3 +/-0.3) for the Cassini division. A phase integral of 1.02 +/- 0.06 is inferred for Rhea, which agrees with values for other icy bodies in the solar system. Rhea eclipse observations indicate the presence of surface materials with both high and low thermal inertias, the former most likely a blocky component and the latter a frost.

Infrared observations of the neptunian system.

The infrared interferometer spectrometer on Voyager 2 obtained thermal emission spectra of Neptune with a spectral resolution of 4.3 cm(-1). Measurements of reflected solar radiation were also obtained with a broadband radiometer sensitive in the visible and near infrared. Analysis of the strong C(2)H(2) emission feature at 729 cm(-1) suggests an acetylene mole fraction in the range between 9 x 10(-8) and 9 x 10(-7). Vertical temperature profiles were derived between 30 and 1000 millibars at 70 degrees and 42 degrees S and 30 degrees N. Temperature maps of the planet between 80 degrees S and 30 degrees N were obtained for two atmospheric layers, one in the lower stratosphere between 30 and 120 millibars and the other in the troposphere between 300 and 1000 millibars. Zonal mean temperatures obtained from these maps and from latitude scans indicate a relatively warm pole and equator with cooler mid-latitudes. This is qualitatively similar to the behavior found on Uranus even though the obliquities and internal heat fluxes of the two planets are markedly different. Comparison of winds derived from images with the vertical wind shear calculated from the temperature field indicates a general decay of wind speed with height, a phenomenon also observed on the other three giant planets. Strong, wavelike longitudinal thermal structure is found, some of which appears to be associated with the Great Dark Spot. An intense, localizd cold region is seen in the lower stratosphere, which does not appear to be correlated with any visible feature. A preliminary estimate of the effective temperature of the planet yields a value of 59.3 +/- 1.0 kelvins. Measurements of Triton provide an estimate of the daytime surface temperature of 38(+3)(-4) kelvins.

Preparing a personal development plan for all members of the dental team.

Personal development plans (PDPs) have been a requirement for NHS hospital staff, Foundation Training and Dental Core Training for some years; however, the General Dental Council (GDC) are changing continuing professional development (CPD) requirements in 2018 (enhanced CPD) making a PDP a requirement for all members of the dental team. A PDP consists of objectives for targeting CPD most relevant to your practice or intended practice to undertake over a defined period to maximise the improvement of your professional development. The aim of this article is to explain how to prepare a PDP ahead of the requirement to utilise its benefits in training and performance for the dental team. This article references a template for all members of the dental team to record their PDP.

Studies on the possible mechanisms of lidoflazine arrhythmogenicity.

Lidoflazine is a calcium channel blocking agent that is effective and safe in the treatment of angina pectoris, but has been reported to be associated with sudden death when administered for the treatment of supraventricular arrhythmias. Studies were performed in dogs to determine if lidoflazine caused a rise in serum digoxin concentration that could cause arrhythmias or if it was directly arrhythmogenic. Dogs received chronic injections of digoxin and then digoxin in combination with lidoflazine. No increase in digoxin concentration was found. Dogs also underwent programmed electrical stimulation while not receiving medications and then after incremental doses of lidoflazine administered intravenously. Lidoflazine did not cause spontaneous ventricular tachycardia and did not lower the threshold of ventricular tachycardia induction. Combined administration of lidoflazine and digoxin did not facilitate arrhythmia induction. These studies do not support a digoxin-lidoflazine interaction or a direct arrhythmogenic action of lidoflazine.

Double representation of lower visual quadrant in prelunate gyrus of rhesus monkey.

The authors have mapped visuotopic organization of prelunate gyrus and adjacent buried cortex in the rhesus monkey. They found two orderly representations of the lower, contralateral visual quadrant in this cortex.

The McCollough effect in rhesus monkey.

After viewing red vertical stripes and green horizontal stripes, the eye subsequently views white vertical stripes as greenish and white horizontal stripes as pinkish. It has been theorized that this phenomenon, known as the McCollough effect, is related to long-tern adaptation of cells tuned for both color and orientation. Such cells have been found in the visual cortex of the rhesus monkey. We asked whether rhesus monkeys, like man, experience a McCollough effect. Two humans and two rhesus monkeys were adapted by requiring them to fixate a spot moving slowly across alternating horizontal and vertical gratings of complementary color. Following adaptation, a test grating whose color changed from red to green or green to red was presented. Humans and monkeys were instructed or trained to release a response lever during the interval that the grating was white. After adaptation, there were orientation-specific changes in all four subjects' responses as would be predicted if both man and monkey were experiencing a McCollough effect.

Hyperventilation syndrome and the assessment of treatment for functional cardiac symptoms.

Three methods of breathing retraining (guided breathing retraining, guided breathing retraining with physiologic monitoring of thoracic and abdominal movement plus peripheral temperature, and guided breathing retraining with physiologic monitoring of thoracic and abdominal movement, peripheral temperature and end-tidal carbon dioxide) were compared with a no-treatment control group to determine the effectiveness of breathing retraining on modifying respiratory physiology and reducing functional cardiac symptoms in subjects with signs associated with hyperventilation syndrome. Of 41 subjects studied, 16 were diagnosed with mitral valve prolapse. Results demonstrated that all 3 methods of breathing retraining were equally effective in modifying respiratory physiology and reducing the frequency of functional cardiac symptoms. Results determined that respiratory rate and subject's perception that training had generalized were the best predictors of treatment success. Furthermore, it was found that subjects with mitral valve prolapse responded as well to treatment as did those without prolapse.

Comparison of noninvasive arrhythmia induction techniques with electrophysiologic studies and evaluation of lorcainide in patients with symptomatic ventricular tachycardia.

Twenty-six patients (19 men and 7 women) with symptomatic ventricular tachycardia (VT) were studied using invasive and noninvasive techniques to induce VT. Of the study population, 12% had syncope and VT on Holter monitoring, 30% had cardiac arrest and 58% had symptomatic VT. All patients had antiarrhythmic agents stopped 5 half-lives before evaluation and then had autonomic profile (upright tilt, cold pressor test, exercise testing and hand grip) as well as programmed electrical stimulation studies performed. Autonomic profile testing induced VT in 5 of 26 patients (19%) and in only 1 patient was the arrhythmia reproducibly induced. All 26 patients had VT induced on electrophysiologic testing; 9 patients had nonsustained and 17 had sustained VT. Lorcainide administered intravenously prevented VT induction in 20 of 26 patients tested, whereas procainamide was effective in 11 of 24 patients. Ten of the 13 not protected by procainamide were protected by lorcainide. Twenty patients were started on long-term lorcainide therapy and followed up for 29 +/- 3.4 months. Five patients have discontinued therapy, 2 because of breakthrough arrhythmias, 2 because of severe sleep-wake disturbances and 1 because of private physician preference. An additional 3 patients died during therapy because of myocardial infarction in 1, progressive myopathy in 1 and sudden death in 1. Sixty percent of patients started on lorcainide therapy have continued. In this patient population, noninvasive induction of VT is not a sensitive or reproducible technique in assessing antiarrhythmic therapy. Furthermore, when selected on the basis of electrophysiologic testing, lorcainide is a well-tolerated and effective antiarrhythmic agent.

Low-dose spiral computed tomography of the thorax: comparison with the standard-dose technique.

RATIONALE AND OBJECTIVES: This study was conducted to determine whether significant reduction in radiation dose (250 mAs-->50 mAs), in chest computed tomography (CT) using volume acquisition affects image quality or the detectability of pathologic findings in the lung and mediastinum. METHODS: Phantom studies were conducted to evaluate resolution and noise level, then a patient study was then done. Fifty consecutive patients (10 normal and 40 abnormal) cases were examined. After a scan (250 mAs, 120OkVp) of the entire thorax, five additional slices (50 mAs, 120kVp) at the level of the abnormality were obtained. Three independent observers evaluated the visibility of normal lung and mediastinal structures, as well as image noise. The mean score was compared between the standard and low doses. In a second study, an independent evaluation of the presence or absence of pathologic findings was made by four observers. RESULTS: Lucite phantom studies demonstrated diminished low-contrast resolution and increased noise level for the low-dose technique. Observers assessed more noise in the low-dose images (P < 0.001). The normal structures were judged to be more visible with standard dose (P < 0.01), but the magnitude of the judged differences was small especially in the lung. No differences were found in the detection of lung and mediastinal abnormalities (P > 0.10). CONCLUSIONS: The low-dose technique was effective in demonstrating pathologic findings for the lung and mediastinum. Low-dose spiral CT should be considered as a viable alternative to standard-dose spiral CT.

The effect of cycloserine on pyridoxine-dependent metabolism in tuberculosis.

Measurements were made of urinary tryptophan metabolites of 13 tuberculosis patients in order to reveal characteristics of pyridoxine-dependent metabolism before and during cycloserine treatment. The abnormally high level of xanthurenic acid excretion in untreated patients suggests a decreased availability of pyridoxal phosphate related to the disease process. Although plasma cycloserine levels were kept high once therapy began, xanthurenic acid excretion before and after tryptophan load became progressively more normal as symptoms diminished. This observation suggests that the convulsions which may sometimes accompany cycloserine administration are not due to a direct pyridoxine antagonism by the drug. Throughout the study, no significant changes in 5-hydroxyindoleacetic acid excretion were observed. Presumably, the metabolic pathway of serotonin is unaffected by tryptophan loading, cycloserine administration, or the apparent pyridoxine depletion associated with tuberculosis.

The effect of glucagon on airway resistance.

Nine subjects with obstructive airway disease took part in this double-blind study of the effect of glucagon in relieving bronchoconstriction compared with isoproterenol or isotonic saline. Drugs were administered via an in-line intermittent positive-pressure breathing unit. FEV1, MEF, PEF, and nitrogen washout data were evaluated. Ten minutes after administration of saline, mean FEV1 and MEF values were significantly reduced from baseline levels (P less than 0.05). Compared to saline, isoproterenol was followed by significantly increased FEV1 and MEF values (P less than 0.05) at both 10 and 30 minutes after medication, indicating reduction in bronchoconstriction. Although the 1-mg dose of glucagon was followed by a mean decrease in these parameters, this decrease was less than that seen after saline alone.

Evaluation of the circle of Willis with three-dimensional CT angiography in patients with suspected intracranial aneurysms.

PURPOSE: To determine the usefulness of CT angiography in the setting of suspected acute subarachnoid hemorrhage or intracranial aneurysm. METHODS: We prospectively studied 68 patients suspected of having subarachnoid hemorrhage or an intracranial aneurysm with noncontrast CT of the head followed immediately by contrast-enhanced helical CT of the circle of Willis with three-dimensional reconstruction. Twenty-seven patients with CT findings positive for subarachnoid hemorrhage or intracranial aneurysm were evaluated with digital subtraction angiography or MR angiography within 12 hours of CT angiography. Patients with negative CT/CT angiography findings were followed up with lumbar puncture. RESULTS: CT angiography showed 23 of 24 aneurysms and 2 of 2 arteriovenous malformations (sensitivity, 96%; specificity, 100%). Aneurysm size ranged from 2 to 40 mm (mean, 7.9 mm). Interobserver variability was 10%. In the 23 cases of subarachnoid hemorrhage, cisternal blood did not limit the three-dimensional reconstruction. Two patients with aneurysms on CT angiography had normal noncontrast scans. CONCLUSIONS: CT angiography of the circle of Willis is a useful technique for evaluation of suspected acute subarachnoid hemorrhage and intracranial aneurysm. It provides anatomic display of intracranial aneurysms, allowing for planning of conventional angiography and surgical approach. In selected cases, CT angiography may eliminate the need for preoperative conventional angiography.

Carotid artery stenosis: optimization of CT angiography with a combination of shaded surface display and source images.

PURPOSE: To evaluate the accuracy of CT angiography of occlusive disease of the carotid arteries using three-dimensional surface-rendered images alone and in conjunction with display of axial source images. METHODS: Forty-eight symptomatic patients had conventional angiography followed by CT angiography within 24 hours. Images of 96 carotid arteries were acquired using contrast-enhanced spiral CT. Image postprocessing was performed on a free-standing workstation to produce 3-D shaded surface display (SSD) images. Two readers independently evaluated the CT angiographic (SSD) images and then reevaluated each case while simultaneously reviewing the SSD and axial source images. Digital subtraction angiograms were evaluated in a separate session and eventually compared with CT angiograms. All evaluations were performed under blinded conditions to control for reader bias. RESULTS: SSD images alone underestimated stenosis relative to angiograms whereas combined SSD and axial images did not. CONCLUSION: SSD angiograms in conjunction with the source images are better than SSD images alone in estimating the degree of stenosis in carotid artery disease.

Effects of spatial-frequency specific adaptation and target duration on visual persistence.

Two experiments investigated the properties of visual persistence as functions of spatial frequency, stimulus duration, and pattern-specific adaptation. In Experiment 1, increasing the duration of high spatial-frequency gratings from 50 to 500 msec decreased the duration of visual persistence produced by that grating to an asymptotic level. However, low-frequency gratings produced a constant estimate of visual persistence independent of presentation time. Also, spatial-frequency specific adaptation reduced the persistence of the high-frequency gratings to this asymptotic level, but the lower frequency persistence estimates already at this level were unaffected (Experiment 2). These findings are related to possible temporal properties of the sustained and transient visual systems.