Maximum Number Of Events Research Articles

(141) Can a Nocturnal Penile Tumescence and Rigidity Test Detect Organic Aetiology of Erectile Dysfunction? A Peripheral and Penile Vascular Study

Abstract Introduction In the diagnostic workup of erectile dysfunction (ED) the Nocturnal Penile Tumescence and Rigidity test (NPTR) is being used less and less because of its inconvenience but also in part because of the intrinsic limits of this test. In particular, the NPTR has been considered very useful to diagnose psychogenic ED when it is positive (normal) but less informative when it is negative (pathological) because of the high incidence of false negatives. Other tests have been suggested to better diagnose an organic ED, especially the dynamic Penile Colour-Doppler Ultrasound (PCDU) to study the penile vascular response and detect a vasculogenic ED. Objective The purpose of the study was to explore the value of a pathological NPTR by investigating relationship between the NPTR result and the peripheral vascular health at the carotid, brachial and cavernous arteries. Methods We conducted an observational study involving patients with ED who had undergone a NPTR as part of their ED diagnostic workup. We assessed their peripheral vascular health through (1) the measurement of the intima-media thickness at the carotid arteries (cIMT), (2) the measurement of the flow-mediated dilation at the brachial artery (FMD), and (3) performing a PCDU. Results Globally, our patients presented with a normal cIMT, FMD and Peak Systolic Value (PSV) in the PCDU. The group with pathological NPTR were significantly older than patients with normal NPTR (55.6 vs 44.1 years, p=0.002), had a higher prevalence of hypertension (50.0 vs 6.8%, p=0.001), longer hypertension duration (8.0 vs 1.3 years, p=0.035), a higher prevalence of diabetes mellitus (42.9 vs 6.8%, p= 0.004), higher blood glucose (111 vs 92 mg/dl, p=0.004) and higher blood triglycerides levels (188 vs 96 mg/dl, p=0.002). Furthermore, they showed lower PSV (46.2 vs 71.0 cm/s, p=0.002) while we did not find significant differences as regards cIMT and FMD between the two groups. Interestingly, the prevalence of patients with pathological PSV (<35 cm/s) was higher among patients with a pathological NPTR but without reaching the statistical significance. However, when adopted an age-dependant cut-off described in the literature (PSV < age x 0.7 + 6.73) the difference between the two groups became significant (50.0 vs 11.4%, p=0.005). Finally, the correlation analysis showed a significant correlation between PSV and the cIMT (-0.352, ρ=0.009), the maximum number of events in the RPTR record (+0.344, ρ=0.012), and the mean tip tumescence (+0.303, ρ=0.036). When corrected for age, these associations lost their statistical significance. Conclusions This study demonstrates the diagnostic value of a pathological NPTR which suggests an organic aetiology of the ED and associates with pathological findings in the PCDU. Age appears to be one of the most important risk factors for ED, even when other risk factors are present. Finally, when using a PCDU to diagnose vasculogenic ED, a cut-off of 35 cm/s might be less sensitive than an age-dependent cut-off to detect early impairments of penile endothelial function. Disclosure No.

Performance evaluation of Standardized Copula‐based Drought Index with Reconnaissance Drought Index and Standardized Precipitation Temperature Index using severity–duration frequency curves over Balochistan, Pakistan

AbstractDrought and aridity are good measures to study climate change that are measured using several indices. In this study, the performance of Standardized Copula‐based Drought Index (SCDI) is compared with Standardized Precipitation Temperature Index (SPTI) and Reconnaissance Drought Index (RDI) for measuring drought in Balochistan province of Pakistan. These standardized drought indices combine the outcomes of De‐Martone Aridity Index (DAI) and UNEP Aridity Index (UAI). SCDI is calculated using probability distributions and copula models that combine the outcomes of UAI and DAI utilizing data of precipitation, potential evapotranspiration (PE), and temperature. Climate data from nine including arid and humid metrological stations are used to study drought conditions in Balochistan province. SCDI outcomes are graphically and numerically compared with SPTI and RDI. Selected drought indices are compared based on frequency of drought and wet events occurred in moderate, severe, and extreme drought categories, which indicate that SCDI has maximum number of events in these categories. It gives better results due to the utilization of more climate data as compared to RDI and SPTI. Severity–duration frequency curves are used to find future projections which shows that drought severity and drought duration have increasing trend with the passage of time. The indices have more differences in results of arid stations. The results indicate that there are no significant chances of drought at lower time scales, but the chances increase with the increase in time scale. The SCDI may also be more useful for agricultural and hydrological droughts due to temperature and PE variables. This study's results will be helpful for climate planning in Balochistan province.

Biomedical Machine Maintenance Scheduling

Tissue banks procure approximately 45,000 tissue donations per year, providing nearly 9,000,000 individuals (about half the population of New York) with life-enhancing and life-saving medical procedures. Proper biobank machine maintenance is imperative to this process. Mandatory forms of maintenance are critical to avoid unexpected malfunctions, which can halt operations and render samples unusable. Each machine has a unique reliability rate within the system; although some can quickly be repaired or replaced, many processes rely on limited machinery where even planned downtime can significantly influence the tissue processing. AlloSource, one of the largest tissue manufacturers in the United States, too often schedules these preventive events unnecessarily or inconveniently, resulting in machines breaking down at inopportune times. In response to these inefficiencies we ask, “What is the best consolidated and standardized equipment maintenance schedule that maximizes monthly maintenance events to ensure increased equipment availability while meeting the demand of the biomedical manufacturing network?” We use an optimization model to consider equipment reliability, downtime, availability, and demand to develop a preventive maintenance schedule. Our model focuses on scheduling the maximum number of events the maintenance crew can conduct each month to ensure vital equipment to the allograft process is available, which provides more opportunities for tissue therapies. In doing so, the maintenance crew is also able to complete more events, driving up annual throughput while driving down equipment downtime.

An In‐Depth Analysis of Lightning Trends in Hurricane Harvey Using Satellite and Ground‐Based Measurements

AbstractSatellite lightning measurements from the Geostationary Lightning Mapper (GLM) and ground‐based measurements from Earth Networks Total Lightning Network (ENTLN) for Hurricane Harvey (2017) are combined to obtain a better representation of intra‐cloud and cloud‐to‐ground lightning and their relationship to intensification and weakening of the hurricane. Through this combination, detection efficiencies of ENTLN and GLM are calculated for the rainband and eyewall of Harvey. In addition, the combined data set is used to derive the cloud flash fraction (CFF) and cloud pulse fraction (CPF) throughout the study period. The results show that flash and pulse rates increase in both the eyewall and rainband prior to rapid intensification in Harvey. The rainband lightning has the highest correlation to Harvey's intensification, where increases in lightning correspond to the largest periods of wind‐speed intensification. The eyewall CFF is also highly correlated to intensification, with minima in eyewall CFF and CPF coinciding with slower intensification periods in Harvey, while increasing CFF and CPF corresponds to more rapidly intensifying periods. Further, GLM flash characteristics including the events per flash, groups per flash, maximum group area, maximum number of events per group, flash footprint, flash energy, and flash duration are tracked and compared to Harvey's wind‐speeds. Nearly all seven flash characteristics show an increase prior to rapid intensification, with the strongest correlation to intensification found with the rainband lightning spatial characteristics. This research represents a step forward in the application of lightning data that can be used in future studies of tropical cyclone intensification and weakening.

Distribution of Solar Flares with Respect to Associated Coronal Mass Ejection (CME) Span During 1996 to 2012

In the present study we have selected 131 events of the flare-CME accompanied by type II radio burst chosen during the period from 1996 to 2012. Statistical analyses are performed to examine the distribution of solar flares with respect to CME span and it was found that from 131 events only 49 lie under the CME span, whereas 82 events are outside the CME span. Our analysis indicates that flare-CME accompanied by type II radio burst does not follow the CSHKP flare-CME model. Under the CME span, 57% events occurred in the northern region and 43% events in the southern region, whereas outside the CME span 51% events occurred in the northern region and 49% events in the southern region. The northern and southern hemispheres between 10 to 20o latitudinal belts are found to be more effective in producing events. We also found that under the CME span the maximum number of events resided at the center, and outside the CME span all the 82 events spread out to one particular side.

The maximum quantum yield controversy. Otto Warburg and the ‘Midwest-Gang’

The maximum quantum yield controversy. Otto Warburg and the ‘Midwest-Gang’

Optical Characteristics of OTD Flashes and the Implications for Flash-Type Discrimination

Abstract Flashes detected by the Optical Transient Detector (OTD) that occur over the continental United States (CONUS) are intercompared with data from the National Lightning Detection Network (NLDN) in order to partition the OTD flashes into ground and cloud flashes. The entire 5-yr OTD dataset for CONUS is analyzed. The statistical distributions of a variety of optical characteristics are examined, including five flash-level attributes (radiance, area, duration, number of optical groups, and number of optical events), and two group-level attributes [the maximum number of events in a group (MNEG), and a closely related parameter, the maximum group area (MGA)]. On average, there were 5.6 optical groups per return stroke in a ground flash, which is in part due to the likelihood that OTD detects interstroke K changes. It was found that return strokes within ground flashes typically produce large optical groups; hence, the MNEG and MGA parameters serve as useful “return-stroke detectors.” The results of this study provide insight on how to construct an algorithm for retrieving the fraction of ground flashes in a set of flashes observed from a satellite lightning imager. Specifically, even though it is shown that the statistical distributions of the optical characteristics for ground and cloud flashes overlap substantially, the mean values of these distributions differ. Hence, a retrieval method that is based on an analysis of the distribution of the means, and that employs the central limit theorem of statistics, is recommended. As the sample size used to compute the means is increased, the overlap in the distributions of the means for ground and cloud flashes is diminished, making ground flash fraction retrieval feasible. Of the seven optical characteristics examined here, the mean MNEG and mean MGA parameters are suggested as being the most useful for discriminating between ground and cloud flashes in the context of this “central limit theorem” approach.

Estimation of intervention effects using first or multiple episodes in clinical trials: The Andersen‐Gill model re‐examined

Randomized trials of interventions against infectious diseases are often analyzed using data on first or only episodes of disease, even when subsequent episodes have been recorded. It is often said that the Andersen-Gill (AG) model gives a biased estimate of intervention effect if there is event dependency over time. We demonstrate that, in the presence of event dependency, an effective intervention may have an indirect effect on disease risk at time t(j) via its direct effect on disease risk at time t(i), i<j, and that the AG model estimates the total effect instead of the direct effect alone. From a clinical and public health perspective, estimation of the total effect is important. Previous simulation studies showed contradictory results about the performance of the AG model in the presence of unobserved heterogeneity across individuals. We show that some of the previous studies unintentionally created informative censoring in their data generating process by including only a certain maximum number of events per individual. We re-ran some previous simulations with and without altering this maximum. With reference to the situations often seen in pneumococcal vaccine trials, we evaluated the performance of the Cox model for time to first episode and the AG model for multiple episodes. We applied these models to re-analyze data from a pneumococcal conjugate vaccine trial. We maintain that a careful clarification of research purpose is needed before one can choose a statistical model, and that the AG model is useful in the estimation of the total effect of an intervention.

Approximations for a Three Dimensional Scan Statistic

Let Xijk,1 ≤ i ≤ N1,1 ≤ j ≤ N2, 1 ≤ k ≤ N3 be a sequence of independent and identically distributed 0 − 1 Bernoulli trials. Xijk = 1 if an event has occurred at the i,j,kth location in a three dimensional rectangular region and Xijk = 0, otherwise. For 2 ≤ mj ≤ Nj − 1,1 ≤ j ≤ 3, a three dimensional discrete scan statistic is defined as the maximum number of events in any m1×m2×m3 rectangular sub-region in the entire N1×N2×N3 rectangular region. In this article, a product-type approximation and three Poisson approximations are derived for the distribution of this three dimensional scan statistic. Numerical results are presented to evaluate the accuracy of these approximations and their use in testing for randomness.

Gender differences and temporal variation in the incidence of type 1 diabetes: results of 8012 cases in the nationwide Diabetes Incidence Study in Sweden 1983–2002

To establish the gender difference amongst newly diagnosed type 1 diabetic patients aged 15-34 years, considering age at diagnosis, temporal trend and seasonal variation at time of diagnosis. A population-based prospective study with a mean annual population at risk of 2.3 million. All departments of medicine, endocrinology and paediatrics and primary health care units in Sweden. Incident cases of diabetes aged 15-34 years at diagnosis 1983-2002. MEASURE INSTRUMENT: Basic characteristics of patients at diagnosis were reported by the diagnosing doctor on a standardized form. Level of ascertainment was estimated at 80-90%. Amongst all incident cases (n = 8012), 74% was diagnosed with type 1 diabetes. The mean annual incidence rate of type 1 diabetes was 12.7/100,000, in men 16.4/100,000 and in women 8.9/100,000. The incidence of type 1 diabetes decreased slowly by increasing age but was in all age groups higher in men, yielding an overall male/female ratio of 1.8. In both genders the incidence of type 1 diabetes decreased in average of 1.0% per year. A seasonal pattern with significantly higher incidence during January-March and lower during May-July was seen in both genders. A clear male predominance of type 1 diabetes was seen in all ages. The temporal trend and the seasonal pattern was similar in men and women. Hence, internal factors related to the gender rather than differences in the exposure to environmental factors seem to explain the consistent male-female bias in the postpubertal risk of developing type 1 diabetes.

Analysis of historical meteor and meteor shower records: Korea, China, and Japan

We have compiled and analyzed historical Korean meteor and meteor shower records in three Korean official history books, Samguksagi which covers the three Kingdoms period (57 B.C.–A.D. 935), Goryeosa of Goryeo dynasty (A.D. 918–1392), and Joseonwangjosillok of Joseon dynasty (A.D. 1392–1910). We have found 3861 meteor and 31 meteor shower records. We have confirmed the peaks of Perseids and an excess due to the mixture of Orionids, north-Taurids, or Leonids through the Monte Carlo test. The peaks persist from the period of Goryeo dynasty to that of Joseon dynasty, for almost one thousand years. Korean records show a decrease of Perseids activity and an increase of Orionids/north-Taurids/Leonids activity. We have also analyzed seasonal variation of sporadic meteors from Korean records. We confirm the seasonal variation of sporadic meteors from the records of Joseon dynasty with the maximum number of events being roughly 1.7 times the minimum. The Korean records are compared with Chinese and Japanese records for the same periods. Major features in Chinese meteor shower records are quite consistent with those of Korean records, particularly for the last millennium. Japanese records also show Perseids feature and Orionids/north-Taurids/Leonids feature, although they are less prominent compared to those of Korean or Chinese records.

Real-time AVHRR forest fire detection in Mexico (1998-2000)

Using our NOAA satellite ground receiving station we have implemented a real-time multispectral fire detection procedure. The Mexican territory is divided into five regions. For each region, time-dependent dynamic temperature threshold values are determined. To avoid solar contamination, nocturnal and early morning Advanced Very High Resolution Radiometer (AVHRR) Local Area Coverage (LAC) images are used. The model determines hot points using channel 3 data. Channel 4 data are used for determining the environmental (surface) temperature. Channel 1 data are used to detect smoke and pixels having a high albedo (4-7%) due to clouds and ground features. Channel 2 data are used to identify land irregularities. Detected hot points are then brought into a geographic information system for ecosystem classification on a national vegetation map which identifies natural protected areas, fragmented forest and agricultural areas. Two daily reports were delivered during 1999 and 2000 to the corresponding national and state authorities so they could take immediate actions. The fire season of 1998 was the most severe season. Satellite imagery detected many fires not only in Mexico but also in Guatemala and Honduras during April and May. South-westerly winds transported the smoke haze over the Gulf of Mexico reaching the USA from New Mexico to southern Florida and sometimes as far north as over the Great Plains. Comparison of the results show that affected areas have been reduced by 7.3 ha per event (1998), 4.0 ha per event (1999) and 2.8 ha per event (2000), respectively. The most affected regions of the country were as follows--in the south: States of Chiapas, Oaxaca, Tabasco and Quintana Roo; in the centre: Estado de México, Guerrero, Jalisco, Zacatecas and Tamaulipas; in the north-east: Coahuila, Nuevo León; and in the north-west: Chihuahua and Sonora. The areas classified as Fragmented Forest show the maximum number of events (80%). This may be because these areas tend to have considerable agricultural activities. It is important to take measures to eliminate these activities.

Approximations for a conditional two-dimensional scan statistic

Let X i, j ,1⩽ i⩽ n 1,1⩽ j⩽ n 2, be a sequence of independent and identically distributed nonnegative integer valued random variables. The observation X i, j denotes the number of events that have occurred in the i, jth location in a two dimensional rectangular region R. For 2⩽m i⩽n i−1, i=1,2 , the two dimensional discrete scan statistic is defined as the maximum number of events in any of the m 1 by m 2 consecutive rectangular windows in that region. Conditional on the total number of events that have occurred in R, we refer to this scan statistic as the conditional two-dimensional scan statistic. Two-dimensional scan statistics have been extensively used in many areas of science to analyze the occurrence of observed clusters of events in space. Since this scan statistic is based on highly dependent consecutive subsequences of observed data, accurate approximations for its distributions are of great value. In this article, based on the scanning window representation of the scan statistic, accurate product-type, Poisson and a compound Poisson approximations are investigated. Moreover, accurate approximations for the expected size of the scan statistic are derived. Numerical results are presented to evaluate the performance of the approximations discussed in this article.

Effect of relative risk and cluster configuration on the power of the one‐dimensional scan statistic

The scan test for clustering in time is based on the maximum number of events in an interval (window) of width w as the window moves across the entire time frame. Power estimates of the scan statistic are simulated for a variety of epidemiologically motivated situations. Two cluster configurations are used: a rectangular pulse, and a triangular pulse designed to emulate environmental contamination. For a rectangular pulse, the relative risk R of disease in the cluster region is R-fold as high as it is for the background region. The power is strongly influenced by the sample size, the relative risk, and the width or duration of the cluster region, whereas the effect of the cluster configuration is small. Using a 5 per cent significance level, a relative risk of 4, a standardized cluster duration of 0.10, a relative window width of 1.5, and a (non-random) sample size of 50, the simulated power is approximately 80 per cent, indicating that the minimum sample size in the cluster region for adequate power is in the 12-32 range for values of the parameters used in this study.

Power of the scan statistic for detection of clustering.

The scan statistic is the maximum number of events in an interval of fixed length w as the subinterval moves over the entire time frame. Previous research derived the null distribution of the scan statistic under the conditional model which assumed that the total number of events was fixed, and under the unconditional model which let the total number of events be a random variable. This paper derives approximations for the power of the scan test for a pulse alternative. Under this alternative, the relative risk of disease on a subinterval (tau, tau + w), tau unknown, is theta-fold as high as it is for other subintervals of length w. Two sets of approximations are given for each model. The first approximation gives highly accurate results, but requires use of a personal computer. The second procedure can be performed on a hand-held calculator and appears very accurate for the cases examined.

Use of the scan statistic to detect time-space clustering.

A test for time-space clustering is proposed based on the scan statistic, the maximum number of events in a 365-day period in each of several geographic units. The data under consideration should consist of the exact date and geographic unit for each event, and data should be available for several years for which the risk of disease can be assumed constant. The statistic is the ratio of the excess number of events summed over all the geographic regions, to the square root of the sum of the variances. This statistic is similar in construction to the Ederer-Myers-Mantel statistic (Biometrics 1964;20:626-38), but does not require that attention be limited to calendar years (January 1-December 31). Unlike other tests for time-space clustering, the scan statistic allows one to calculate measures of attributable risk and effect size. Data concerning adolescent suicide are used to illustrate the procedure. The tables and asymptotic formulas given for the mean and variance of the proposed statistic should be useful in the evaluation of both clustering in time and in time-space.

Testing for a Pulse in Seasonal Event Data

Most tests for seasonal clustering are sensitive to the peak in incidence in some season (90-day interval) followed by a trough 6 months later. We present two statistics sensitive to a relatively sharp increase in disease incidence for a season superimposed on a constant incidence over the entire year: the ratchet scan, based on the maximum number of events in k consecutive months, and the continuous circular scan, the maximum number of events in d consecutive days. We tabulate the tail distribution of the ratchet scan for N less than or equal to 35 and k = 2 and 3, and find the asymptotic distribution which is applicable for N greater than or equal to 50 when k = 2 or 3. We evaluate an approximation for the distribution of the continuous scan. The statistics are applied to investigate seasonal clustering of adolescent suicide in the United States. An illustration is given of the application of the circular scan, and a small simulation study and the example are used to compare the statistics with others proposed in the literature.

Explosive Cyclogenesis over the Northeast Pacific Ocean

Abstract Data on explosively developing extratropical cyclones over the northeast portion of the Pacific Ocean have been compiled. A climatology of those events which deepened by 1 Bergeron (24 mb day−1 deepening at 60°N) or more is discussed. The maximum number of events occurred in October and the minimum number in August. The initial positions of such storms was most frequently in the area between 40 to 50°N and 140 to 170°W.