Quantifying social segregation in large-scale networks

We present a measure of social segregation which combines mobile phone data and income register data in Oslo, Norway. In addition to measuring the extent of social segregation, our study shows that social segregation is strong, robust, and that social networks are particularly clustered among the richest. Using location data on the areas where people work, we also examine whether exposure to other social strata weakens measured segregation. Lastly, we extend our analysis to a large South Asian city and show that our main results hold across two widely different societies.

Intra-Annual Changes in Waterborne Nanophyetus salmincola

An analysis of daily water samples collected from an index site on Big Soos Creek, Washington indicated intra-annual differences in the concentrations of waterborne Nanophyetus salmincola. Waterborne concentrations, quantified as gene copies/L, peaked during the fall (October-November 2016), decreased to very low concentrations over the winter (January-March 2017), and then increased in the spring and throughout the summer. High waterborne concentrations of N. salmincola DNA (2 × 10⁶ gene copies/L) corresponded with live N. salmincola cercariae (mean = 3 cercariae/L) that were detected in companion water samples. Spikes in waterborne N. salmincola concentrations in October and November typically coincided with increases in streamflow; this combination resulted in elevated infection pressures during high water events in the fall. The peak in waterborne N. salmincola concentrations corresponded with an accompanying peak in tissue parasite density (metacercariae/posterior kidney) in Coho Salmon Oncorhynchus kisutch that were reared in the untreated water.

Product diffusion through on-demand information-seeking behaviour

Most models of product adoption predict S-shaped adoption curves. Here we report results from two country-scale experiments in which we find linear adoption curves. We show evidence that the observed linear pattern is the result of active information-seeking behaviour: individuals actively pulling information from several central sources facilitated by modern Internet searches. Thus, a constant baseline rate of interest sustains product diffusion, resulting in a linear diffusion process instead of the S-shaped curve of adoption predicted by many diffusion models. The main experiment seeded 70 000 (48 000 in Experiment 2) unique voucher codes for the same product with randomly sampled nodes in a social network of approximately 43 million individuals with about 567 million ties. We find that the experiment reached over 800 000 individuals with 80% of adopters adopting the same product—a winner-take-all dynamic consistent with search engine driven rankings that would not have emerged had the products spread only through a network of social contacts. We provide evidence for (and characterization of) this diffusion process driven by active information-seeking behaviour through analyses investigating (a) patterns of geographical spreading; (b) the branching process; and (c) diffusion heterogeneity. Using data on adopters' geolocation we show that social spreading is highly localized, while on-demand diffusion is geographically independent. We also show that cascades started by individuals who actively pull information from central sources are more effective at spreading the product among their peers.

Mapping poverty using mobile phone and satellite data

Poverty is one of the most important determinants of adverse health outcomes globally, a major cause of societal instability and one of the largest causes of lost human potential. Traditional approaches to measuring and targeting poverty rely heavily on census data, which in most low- and middle-income countries (LMICs) are unavailable or out-of-date. Alternate measures are needed to complement and update estimates between censuses. This study demonstrates how public and private data sources that are commonly available for LMICs can be used to provide novel insight into the spatial distribution of poverty. We evaluate the relative value of modelling three traditional poverty measures using aggregate data from mobile operators and widely available geospatial data. Taken together, models combining these data sources provide the best predictive power (highest r² = 0.78) and lowest error, but generally models employing mobile data only yield comparable results, offering the potential to measure poverty more frequently and at finer granularity. Stratifying models into urban and rural areas highlights the advantage of using mobile data in urban areas and different data in different contexts. The findings indicate the possibility to estimate and continually monitor poverty rates at high spatial resolution in countries with limited capacity to support traditional methods of data collection.

Correlation length exponent in the three-dimensional fuse network

We present numerical measurements of the critical correlation length exponent nu in the three-dimensional fuse model. Using sufficiently broad threshold distributions to ensure that the system is the strong-disorder regime, we determine nu to be nu=0.83+/-0.04 based on analyzing the fluctuations of the survival probability. This value is different from that of ordinary percolation, which is 0.88.

Clinical prediction of cervical spine injuries in children. Radiographic abnormalities

During the seven-year period from 1976 through 1982, 2133 cervical spine radiographs were obtained for children less than 18 years of age at two hospitals in Tucson. Twenty-five children (1.2%) had x-ray evidence of a cervical spine injury, with a male to female ratio of 4:1. Vehicular accidents accounted for 36% of cervical spine radiographic abnormalities, and sports or playground accidents accounted for an additional 36%. In an attempt to find clinical predictors that might identify x-ray abnormalities, we reviewed the medical records of these 25 children with abnormalities and 713 randomly selected children without x-ray evidence of cervical spine injuries for the following: method of injury, presenting complaints, physical examination findings, therapy, and complications. No single clinical predictor had a sensitivity of 100% when considered in isolation, but clinical assessment consisting of EITHER a complaint of neck pain OR involvement in a vehicular accident with head trauma would have correctly identified all 25 cases of cervical spine injury. If this information had been used prospectively, the number of cervical spine radiographs ordered would have been reduced by 32%. We conclude that the use of this clinical "marker" would have positively identified all children with cervical spine injuries and would have reduced by one third the cost and radiation exposure associated with cervical spine radiographs. Because of the serious consequences of missing a cervical spine injury, we suggest that other studies confirm these results before this information is accepted as a recommendation.

Total digital radiology department: spatial resolution requirements

The minimum spatial resolution required for a total digital radiology department has yet to be defined. A pilot study designed to provide this information was performed. Abnormal and normal radiographic images of children were digitized and redisplayed on film at spatial resolutions of 5.0, 2.5, 1.25, and 0.625 lp/mm. These resolutions are comparable to a digital display of a 14 X 14 in. chest image having pixel elements of 4096 X 4096, 2048 X 2048, 1024 X 1024, and 512 X 512, respectively. Contrast resolution was maintained at 12 bits or 4096 gray levels. The three phases of data acquisition were (1) the standard analysis of receiver operating characteristics, (2) a checklist evaluation of the "seeability" of important structures, and (3) a comparison of all resolutions and a discernment of usability. Fifteen radiologists participated in the study. On the basis of the pediatric cases used, the results showed that the needed spatial resolution for a total digital radiology department may be around 2.5 lp/mm (2048 X 2048). Checklist data on seeability of structures and comparisons of all resolutions give information on specific changes that are occurring as the resolution is decreased, and, when included with the receiver-operating-characteristic data, they become a major component in developing a resolution standard. The finding that 2.5 lp/mm is the required spatial resolution makes construction of a total digital radiology department possible with present state-of-the-art technology.

Recognition of bladder tumors by excretory urography

Bladder tumors initially may be diagnosed by excretory urography in patients undergoing the examination because of specific symptoms or unrelated complaints. Among seven strategies tested by six experienced readers, the combination of early, full-bladder, and postvoiding anteroposterior radiographs was most successful in identifying bladder tumors in a series including 20 cases of biopsy-proved bladder tumor and 19 cases of cystoscopically normal bladders. The postvoiding radiograph, when viewed alone, was the single most valuable projection, and resulted in the correct diagnosis of 14 cancers that were not appreciated on any other single radiograph for a given case. The addition of oblique projections to the other three views did not significantly increase diagnostic sensitivity.

Obstructive sleep apnea in Treacher-Collins syndrome

Studies of the Treacher-Collins syndrome have emphasized hearing and surgical considerations. Although craniofacial anomalies have been associated with respiratory disorders in infancy, the presence of such problems in older children has not been emphasized. An eight-year-old with Treacher-Collins syndrome presented a history of recent behavioral problems at home, poor attention span and performance in school, daytime somnolence, and sleep apnea with relatively long periods of chest movement but no airflow. He also had abnormal sleep behavior consisting of rocking to and fro on his hands and knees, often to such an extent that his nose became abraded. ICU monitoring with observation and recording of sleep patterns and sounds, and fluoroscopy of his upper airway utilizing cineradiography while asleep confirmed the diagnosis of obstructive sleep apnea. The patient subsequently underwent an orthognathic surgery consisting of insertion of rib bone grafts after anterior advancement of his mandible. This procedure resulted in disappearance of the obstructive sleep apnea and associated symptoms. Because of micrognathia, patients with Treacher-Collins syndrome are at high risk for developing obstructive sleep apnea. Surgical correction of their deformities can result in improvement in cosmetic appearance as well as in resolution of the obstructive episodes with improvement in performance and behavior.

Controlled study of the cytotoxic food test

The cytotoxic food test was not found to be an accurate method for diagnosing atopic reactions to foods. Claims that the test correlated with other untoward reactions to foods (eg, headache, diarrhea, fatigue) could not be corroborated. The test itself is time-consuming, dependent on subjective interpretation, and inconsistent in results when repetitive runs are performed on the same patient.