Effects of stimulus number and target-to-distractor ratio on the performance of random array letter cancellation tasks

Cancellation tests are commonly used in the clinical assessment of visuospatial function, but there has been little study of task characteristics influencing performance. This study was designed to assess factors which affect cancellation performance. Sixteen healthy subjects sequentially performed four random-array letter cancellation tasks. The forms contained 50 and 100 stimuli and target:distractor (T/D) ratios of 1:4 and 1:9 with target letter "A" and randomly selected letter distractors. The primary performance measure was calculated as the number of correctly cancelled targets divided by the time to complete the task, corrected for accuracy. This measure revealed a strong effect of T/D ratio (p < .0001), with performance adversely affected by higher proportion of distractors. There was no effect of stimulus number. This suggests that T/D ratio should be considered in cancellation test design and interpretation.     

Multiyear and Seasonal Variation of Infiltration from Storm-Water Best Management Practices

Reduction of storm-water volumes through infiltration is becoming a commonly applied practice in the effort to mitigate the negative hydrologic impacts commonly associated with land development. The hydrologic impacts generally include increases in both the volume and peak flow rate of runoff along with an associated decrease in groundwater recharge. Infiltration best management practices (BMPs) are the foundation of many low impact development and Green infrastructure practices. As the movement to volume reduction is a relatively recent concept, there remains a lack of detailed long-term monitoring data to support the implementation of storm-water infiltration BMPs. Two storm-water infiltration BMPs on the campus of Villanova University located in Southeastern Pennsylvania have been continuously monitored to determine the long-term and seasonal variation related to the engineered infiltration of storm-water runoff. The analysis of continuous monitoring data indicates that both BMPs show considerable seasonal variation but exhibit no evidence of a systematic decrease in performance to date. The seasonal variation of the BMPs is explained primarily by the temperature dependency of the viscosity of water.     

Seasonal distribution of acute myocardial infarction in the second National Registry of Myocardial Infarction

OBJECTIVES: This observational study sought to determine whether cases of acute myocardial infarction (AMI) reported to the second National Registry of Myocardial Infarction (NRMI-2) varied by season. BACKGROUND: The existence of circadian variation in the onset of AMI is well established. Examination of this periodicity has led to new insights into pathophysiologic triggers of atherosclerotic plaque rupture. Although a seasonal pattern for mortality from AMI has been previously noted, it remains unclear whether the occurrence of AMI also displays a seasonal rhythmicity. Documentation of such a pattern may foster investigation of new pathophysiologic determinants of plaque rupture and intracoronary thrombosis. METHODS: We analyzed the number of cases of AMI reported to NRMI-2 by season during the period July 1, 1994 to July 31, 1996. Data were normalized so that seasonal occurrence of AMI was reported according to a standard 90-day length. RESULTS: A total of 259,891 cases of AMI were analyzed during the study period. Approximately 53% more cases were reported in winter than during the summer. The same seasonal pattern (decreasing occurrence of reported cases from winter to fall to spring to summer) was seen in men and women, in different age groups and in 9 of 10 geographic areas. In-hospital case fatality rates for AMI also followed a seasonal pattern, with a peak of 9% in winter. CONCLUSION: The present results suggest that there is a seasonal pattern in the occurrence of AMIs reported to NRMI-2 that is characterized by a marked peak of cases in the winter months and a nadir in the summer months. This pattern was seen in all subgroups analyzed as well as in different geographic areas. These findings suggest that the chronobiology of seasonal variation in AMI may be affected by variables independent of climate.     

Is stroke incidence related to season or temperature? The Oxfordshire Community Stroke Project

BACKGROUND: A winter excess of ischaemic stroke has been found in mortality and hospital-based studies. It is often assumed that this is due to seasonal variation in stroke incidence and several pathophysiological explanations have been proposed. We studied the incidence of stroke in relation to season and outside temperature. METHODS: The data came from a community-based study of first ever in a lifetime stroke in a defined population of about 105 000. 675 such strokes were registered over four years and the month of inset was analysed separately for cerebral infarction, primary intracerebral haemorrhage, and subarachnoid haemorrhage. FINDINGS: There was no significant seasonal variation. The incidence of primary intracerebral haemorrhage was increased at low temperatures, but there was no significant relation between the incidence of ischaemic stroke or subarachnoid haemorrhage and temperature. INTERPRETATION: The widely reported winter excess of ischaemic strokes may be an artifact due to referral bias in hospital-based studies and increased case fatality during the winter in mortality studies.     

Seasonal variation in the incidence of Hodgkin's disease

Earlier literature suggested there may be a seasonal rhythm of onset of Hodgkin's disease. This issue has been re-examined using population-based prospectively-collected data with high ascertainment levels. The Data Collection Study (DCS) of the Leukaemia Research Fund (LRF) Centre for Clinical Epidemiology (University of Leeds) generated the information used, which was based on a population of 13.5 million--about one quarter of England and Wales--over 10 years. The RYE histopathological classification was employed. The findings show that in patients with nodular sclerosing histopathology there was a highly significant circannual rhythm with a low amplitude (extent of seasonal variation) and a peak in March. A significant, but different, rhythm with a high amplitude and a peak in August was found in lymphocyte predominant Hodgkin's disease. However, this finding is less certain, due to smaller numbers and a lower significance level. The main conclusion is that there is a highly significant seasonality in nodular sclerosing Hodgkin's disease. The findings provide further evidence that nodular sclerosing and lymphocyte predominant may be two different diseases. The differing seasonality rhythms may provide aetiological clues.     

The role of "one-shot" intravenous pyelogram in evaluation of penetrating abdominal trauma

STUDY OBJECTIVE: Many studies on seasonality in Down syndrome (DS) have been performed and have come to different conclusions. It is suggested that seasonal variation in hormone production by the hypothalamus-pituitary-ovarian axis just before ovulation leads to seasonality in conception rates of DS. This study aimed to determine whether there is seasonal variation in the prevalence of DS at birth as a proxy for seasonality in DS at conception. DESIGN: All the English and Dutch articles on this topic were reviewed. Articles published between 1966 and January 1996 were traced by Medline, and by the reference lists. MAIN RESULTS: Twenty articles met the criteria for inclusion. Although seven of these studies reported seasonality in DS prevalence, no consistent seasonal pattern was found in DS at birth in these studies, or in the remaining studies. A seasonal pattern could not have been masked by the effects of maternal age, induced abortions, shortened gestation, or misclassification of DS. CONCLUSION: Seasonality in the prevalence of DS at birth does not exist. Evidence did not support the suggestion that DS occurrence is related to seasonality in hormone production.     

Elevation of the serum bilirubin diconjugate fraction provides an early marker for cholestasis in the rat

OBJECTIVES: To determine whether the sisters of women with premature ovarian failure (POF) showed a response to gonadotropin stimulation comparable to that of anonymous ovum donors. DESIGN: Historical cohort study. SETTING: Records of 228 consecutive ovum recipients in an academic assisted reproductive technology program. PATIENT(S): Criteria for inclusion were oocyte recipients age < or = 40 years, FSH > 18 mIU/mL (conversion factor to SI unit, 1.00), and/or failure to respond appropriately to controlled ovarian hyperstimulation (COH). Seventy-nine recipients were classified on the basis of whether they received oocytes from anonymous donors (group I, n = 66) or sister donors (group II, n = 13). MAIN OUTCOME MEASURE(S): Controlled ovarian hyperstimulation response, pregnancy rates (PRs), and implantation rates. RESULT(S): The ages of the donors to groups I and II were comparable (31.1 +/- 16.7 versus 29.8 +/- 7.2 years), but those in group II exhibited a higher baseline FSH level (12.8 +/- 2.1 versus 8.6 +/- 5.8 mIU/mL). Group II versus I had a relative risk of 5.1 for cancellation (4 of 13 [30.8%] versus 4 of 66 [6.1%], respectively). In completed cycles of groups I and II, respectively, there was no difference in serum E2 on the day of hCG administration (2,356 +/- 826 versus 1,847 +/- 843 pg/mL; conversion factor to SI unit, 3,671), number of oocytes retrieved (25 +/- 14 versus 22 +/- 13), number of embryos transferred (4.4 +/- 2.1 versus 4.0 +/- 1.0), spontaneous abortion rate (22.7% versus 25.0%), PR (35.5% versus 36.4%), and implantation rate (16.2% versus 16.4%). CONCLUSION(S): There is an increased cancellation rate and, consequently, an overall trend toward decreased ovarian response to gonadotropin stimulation in the sisters of patients with POF. Despite these factors, the implantation rates and PRs of embryos derived from patients reaching retrieval were similar to those from anonymous donors. We recommend counseling women with POF that their sisters may not be ideal ovum donors.     

Absence of seasonal variation in malaria parasitaemia in an area of intense seasonal transmission

Parasitological surveys carried out in two villages of the Kilombero district of Tanzania indicated a very high prevalence of Plasmodium falciparum parasitaemia throughout the year (all ages mean prevalence = 69.2%) and a low, unstable prevalence of P. malariae (all ages mean prevalence = 4.5%). Fevers (temperature > or = 37.5 degrees C) in both children and adults showed irregular changes in prevalence over time, but there was no seasonal pattern. Neither was there seasonal variation in either P. falciparum parasite prevalence or parasite densities. This was despite marked seasonality in vectors caught in CDC light-traps and in estimated sporozoite inoculations determined by ELISA. The estimated mean annual inoculation rate was extremely high, over 300 infectious bites per person per year, the main vectors being members of the A. gambiae complex and Anopheles funestus. There was considerable variation between houses but even in houses with relatively low mosquito numbers the inoculation rate was sufficient to maintain a maximal P. falciparum prevalence. Heterogeneities in exposure cannot explain why the parasite prevalence is not always 100%. In areas of such high transmission, parasitaemias are likely to be determined mainly by the interaction of schizogony and anti-blood stage immunity, since parasites arising from new inoculations generally comprise only a small proportion of the total in the circulation. In any one individual, this will lead to periodic fluctuations in levels of parasitaemia. These are unlikely to show a close relationship to either seasonal variation in inoculations or to differences between households in the local inoculation rate.     

Rhegmatogenous retinal detachments. Seasonal variation and incidence

Seasonal variations in the relative incidence of rhegmatogenous retinal detachment were reported as a trend in several studies on the database of relatively limited cohort sizes. PATIENTS AND METHODS: An analysis on this topic was performed with a long-term database. A total of 3073 files of patients with rhegmatogenous retinal detachment, covering 11 years of observation, were reviewed for this study. Patients with signs of long-standing detachment or other predisposing diseases were excluded, so that a basic study population of 2314 patients remained for the analysis. RESULTS: The averaged seasonal incidence of rhegmatogenous detachments revealed a significant (P < 0.005) mid-summer peak (n in July = 228) and a winter trough (mean of December-January = 161; difference = 36%). Phase and curve fitting of the seasonal variations in the number of retina detachment cases was similar to the seasonal variation of the astronomic duration of the day (P < 0.001). The relation was closer compared to the average duration of light exposure per day calculated from behavioural data and the astronomic length of light phase (P < 0.0002). CONCLUSION: This long-time study revealed a close correlation of the relative seasonal incidence of retinal detachment and the seasonal variation of light hours per day. So far, this observations cannot be explained pathogenetically. Two basic hypotheses ought to be investigated further: (1) The influence of light on the generation of toxic oxygen radicals and the subsequent destruction of the vitreous and (2) possible light-induced changes in vitreoretinal adhesion.     

Intraoperative pacemaker dysfunction caused by the use of electrocautery during a total hip arthroplasty

PURPOSE: To evaluate if there is a seasonal pattern to the incidence of endogenous uveitis in south-western Finland with special reference to acute anterior uveitis. METHODS: The incidence rates per month of the 414 new uveitis cases from years 1980-82 and 1988 in the district of Turku University Hospital were calculated. The months of the year were grouped into warm (June to September), transitional (April, May, October, November), and cold (December to March) seasons based on the mean air temperature of the months in Turku. RESULTS: We observed a statistically significant increase in the incidence of all uveitis cases in the warm and transitional seasons compared with the cold season (p=0.030 and p=0.008 respectively). A similar seasonal trend was found among anterior uveitis cases, but not among the intermediate, posterior or panuveitis cases. The incidence of acute anterior uveitis cases was higher in the transitional than in the cold season (p=0.025). No seasonal variation of the incidence was found in the subgroup of acute anterior uveitis where ankylosing spondylitis had been confirmed (p=0.70). CONCLUSION: The present data suggests that there is seasonal variation of the incidence of uveitis in south-western Finland.     

Bone and joint tuberculosis in the field of orthopedics

In Japan the number of patients with bone and joint tuberculosis has been dramatically decreasing since the beginning of 1980's. The number of patients was 1626 in 1978 according to statistics of tuberculosis patient in Japan. This was only 2.02% of new tuberculosis patients of Japan in 1978. Since that time the number of patients with bone and joint tuberculosis, in Japan, has been in steady decline. The number was only 675 patients in 1996. This was only 1.34% of new tuberculosis patients. The rate of new infections also decreased. Recently due to the development of computed tomography, magnetic resonance imaging and so on, patients with bone and joint tuberculosis can be diagnosed early, with great certainty. Curettage of infected focus and bone grafting via anterior approach has resulted in consistently improved results. While there are many reports of about the operative treatment with spinal instruments for spinal tuberculosis, artificial materials must be implanted with great care.     

Apoptosis signaling by death receptors

How do stimulus size and item number relate to the magnitude and direction of error on center estimation and line cancellation tests? How might this relationship inform theories concerning spatial neglect? These questions were addressed by testing twenty patients with right hemisphere lesions, eleven with left hemisphere lesions and eleven normal control subjects on multiple versions of center estimation and line cancellation tests. Patients who made large errors on these tests also demonstrated an optimal or pivotal stimulus value, i.e., a particular size center estimation test or number of lines on cancellation that either minimized error magnitude relative to other size stimuli (optimal) or marked the boundary between normal and abnormal performance (pivotal). Patients with right hemisphere lesions made increasingly greater errors on the center estimation test as stimuli were both larger and smaller than the optimal value, whereas those with left hemisphere lesions made greater errors as stimuli were smaller than a pivotal value. In normal subjects, the direction of errors on center estimation stimuli shifted from the right of true center to the left as stimuli decreased in size (i.e., the crossover effect). Right hemisphere lesions exaggerated this effect, whereas left hemisphere lesions diminished and possibly reversed the direction of crossover. Error direction did not change as a function of stimulus value on cancellation tests. The demonstration of optimal and pivotal stimulus values indicates that performances on center estimation and cancellation tests in neglect are only relative to the stimuli used. In light of other studies, our findings indicate that patients with spatial neglect grossly overestimate the size of small stimuli and underestimate the size of large stimuli, that crossover represents an "apparent" shift in error direction that actually results from normally occurring errors in size perception, and that the left hemisphere is specialized for one aspect of size estimation, whereas the right performs dual roles.     

The mode of onset of rheumatoid arthritis and seasonal variations

The aim of the study was to establish age and sex distribution, seasonal variations, and mode, of onset in a sample of patients with rheumatoid arthritis. One hundred eighty nine patients (146 women and 43 men), whose age ranged from 18 to 77 yrs. (mean age 49.1, SD 12.93) were included in the survey. In majority of patients the disease started between 31-50 years, whereas in the age group from 21-30 it occurred more frequent in women, and in the age group from 51-60 in men. The onset of rheumatoid arthritis was in almost equal proportions acute or insidious, regardless sex. No difference was found concerning onset of the disease and seasonal variations. However there was a statistically significant correlation between mode of the onset and seasonal variations (P < 0.05). Rheumatoid arthritis started abruptly more often in springtime, and more insidiously in autumn, whereas in summer and winter there was an equal number of patients with acute or insidious onset of the disease.     

The open surgical approach to subglottic hemangioma

The monthly distribution of relapses in ulcerative colitis was analysed retrospectively to assess seasonal variation. In 338 patients who were regularly followed up at the colitis clinic, 1013 relapses occurred during the period 1977 to 1988. A peak of relapses occurred in the spring and autumn, with a decrease in the summer; the ratio of the observed to expected number of relapses was 201:255.3 for the summer, 289:252.6 for the autumn, 243:249.8 for the winter, and 280:255.3 for the spring. In contrast, month of diagnosis was evenly distributed without seasonality. The data support the concept that exacerbations in ulcerative colitis are influenced by seasonal factors.     

Studies on the chlorination of zircon: Part I. Static bed investigations

Carbochlorination is an important unit operation in the processing of zirconium resources. In the article, the use of different reducing agents in zircon chlorination, to produce zirconium tetrachloride, has been examined on thermodynamic and other considerations. While numerous workers have investigated zircon chlorination, a literature survey shows that there is a wide variation in the reported effect of various process parameters on the chlorination rate and a wide scatter in the values for kinetic parameters such as order of reaction, activation energy, rate constant as also the rate law expression. This work is an extensive study on zircon chlorination and the article discusses the effect of process parameters such as charge particle size, gas and solid composition, gas flow rate, temperature, reaction duration, etc. on the chlorination rate, over a much wider range of the parameter values. During investigations in the static bed chlorinator, it was noticed that the initial rate and the total extent of chlorination are proportional to the exposed surface of the solid zircon-coke charge but independent of the depth or amount of the charge. Further, the stalled chlorination could be reactivated by remixing the solid charge. Also, while the reaction rate in general increased as the charge became finer, the effect of zircon particle size was much more predominant. The activation energy value for the chlorination showed a wide variation with other operating conditions. Likewise, the order of reaction with respect to chlorine decreased from two to zero as the chlorine concentration in the gaseous atmosphere increased. Interestingly, the chlorination rate initially increased with gas flow rate, then decreased, before finally becoming independent of the gas flow rate. Results also indicated that there is an optimum charge composition that yields the maximum chlorination rate and the article discusses the effect of the zircon to coke particle number ratio in the initial charge on the chlorination kinetics. With the help of these observations, it is possible to explain the wide variation in the reported effect of the various process parameters on zircon chlorination.     

Seasonal variation in spontaneous abortions

Using a national sample of hospital discharges, we found identical seasonal patterns for spontaneous abortions and conceptions but no significant seasonal variation in the rate of spontaneous abortions per 1,000 conceptions. The differences between our findings and those of previous investigators of spontaneous abortion may reflect our more comprehensive definition of spontaneous abortion, our more complete estimate of the monthly number of conceptions, and our more rigorous statistical analysis. The periodic regression analysis (PRA) reported in our study may be useful in other studies that monitor short-term trends.     

Seasonal allergic rhinitis and pollen count (a 5-year survey in Budapest)

The authors compared the seasonal symptoms and the pollen allergen spectrum of pollen allergy with the 5-year aeropalynological data in Budapest. They summarized the average of symptom scores based on the diaries of 105 pollen allergic patients (mainly children) suffering from seasonal allergic rhinoconjunctivitis. The pollen allergen spectrum of the patients was defined. They constructed a local pollen calendar on the basis of the first regular pollen counting in Budapest, which had been done by them for 5 years. The symptom scores grew parallel with the increasing number of grass and ragweed pollen. Tree pollen allergy was found in 7.6 per cent of the patients. In spite of the high number of three pollen in the air in March and April the patients did not have too many complaints according to their symptom scores. Grass pollen allergy was found in 67.6 per cent of the patients and in the grass pollen season (May-July) the characteristic clinical symptoms were expressed. Weeds (in 64.8 per cent of the patients), especially ragweed (in 59.0 per cent of the patients) caused the most significant complaints in the late summer--autumn (August, September and partly October) period. Ragweed and other weeds play an important role in the etiology of seasonal allergic diseases in Hungary. The authors call the attention to the necessity of measures taken against the spread of ragweed.     

Multiple endocrine neoplasia syndrome, type 2B

It was investigated whether there is a seasonal variation in sex ratio at birth in Germany. The analysis was based on records from the German Bureau for Statistics, covering the period from 1946 to 1995. A highly significant (P < or = 0.001), albeit low-amplitude rhythm was found with two peaks in May and December, and two nadirs in March and October. No correlations were found between sex ratios and seasonal birth rates during this period.     

Gender does not affect fetal heart rate variation

There is a widespread but erroneous view among the lay public that there is a difference in the baseline fetal heart rate between male and female fetuses. It has been suggested that this perception might reflect an actual difference in fetal heart rate variability. Therefore, we studied the fetal heart rate variation in 79 white European women using the Sonicaid System 8002 computer. Fourty-four of the fetuses were male and 35 were female. There was no significant gender difference in any measured aspect of fetal heart rate variation.     

Use of coronary angiography and revascularization procedures following acute myocardial infarction. A European perspective

AIMS: There is little evidence to inform routine practice in the use of coronary angiography and revascularization procedures after acute myocardial infarction. Large differences in the uptake of these procedures have been reported but representative data are scarce. Outcome studies have produced opposing conclusions concerning the impact of the high rate of these cardiac procedures. METHODS AND RESULTS: A population-based patient sampling approach was utilized to identify routine practice in representative samples from 11 European countries. Data were collected retrospectively on treatment in the 6 months following acute myocardial infarction (n=2807). There was wide variation in utilization of coronary angiography and revascularization procedures. Even after restricting the analysis to patients <65 years (n=1262), there remained a 6 13 fold variation in the use of these procedures. A decreased likelihood of undergoing these procedures was associated with older age. In addition, there was an independent and negative association between female sex and utilization of coronary angiography and coronary artery bypass grafting (CABG). CONCLUSION: The effect on patient outcome of the observed variation in use of these procedures is not known but has important cost and resource implications for the health services. Outcome research is needed to define patient selection criteria and to measure the cost-utility of different angiography and revascularization rates.