Absorption of wireless radiation in the child versus adult brain and eye from cell phone conversation or virtual reality.

Children's brains are more susceptible to hazardous exposures, and are thought to absorb higher doses of radiation from cell phones in some regions of the brain. Globally the numbers and applications of wireless devices are increasing rapidly, but since 1997 safety testing has relied on a large, homogenous, adult male head phantom to simulate exposures; the "Standard Anthropomorphic Mannequin" (SAM) is used to estimate only whether tissue temperature will be increased by more than 1 Celsius degree in the periphery. The present work employs anatomically based modeling currently used to set standards for surgical and medical devices, that incorporates heterogeneous characteristics of age and anatomy. Modeling of a cell phone held to the ear, or of virtual reality devices in front of the eyes, reveals that young eyes and brains absorb substantially higher local radiation doses than adults'. Age-specific simulations indicate the need to apply refined methods for regulatory compliance testing; and for public education regarding manufacturers' advice to keep phones off the body, and prudent use to limit exposures, particularly to protect the young.

Recent diarrhea is associated with elevated salivary IgG responses to Cryptosporidium in residents of an eastern Massachusetts community.

BACKGROUND: Serological data suggest that Cryptosporidium infections are common but underreported. The invasiveness of blood sampling limits the application of serology in epidemiological surveillance. We pilot-tested a non-invasive salivary anti-Cryptosporidium antibody assay in a community survey involving children and adults. MATERIALS AND METHODS: Families with children were recruited in a Massachusetts community in July; symptoms data were collected at 3 monthly follow-up mail surveys. One saliva sample per person (n = 349) was collected via mail, with the last survey in October. Samples were analyzed for IgG and IgA responses to a recombinant C. hominis gp15 sporozoite protein using a time-resolved fluorometric immunoassay. Log-transformed assay results were regressed on age using penalized B-splines to account for the strong age-dependence of antibody reactions. Positive responses were defined as fluorescence values above the upper 99% prediction limit. RESULTS: Forty-seven (13.5%) individuals had diarrhea without concurrent respiratory symptoms during the 3-month-long follow-up; eight of them had these symptoms during the month prior to saliva sampling. Two individuals had positive IgG responses: an adult who had diarrhea during the prior month and a child who had episodes of diarrhea during each survey month (Fisher's exact test for an association between diarrhea and IgG response: p = 0.0005 for symptoms during the prior month and p = 0.02 for symptoms during the entire follow-up period). The child also had a positive IgA response, along with two asymptomatic individuals (an association between diarrhea and IgA was not significant). CONCLUSION: These results suggest that the salivary IgG specific to Cryptosporidium antigens warrants further evaluation as a potential indicator of recent infections.

Effect of head-out water immersion on cardiorespiratory response to dynamic exercise.

Head-out water immersion is known to produce several cardiopulmonary adjustments at rest due to a cephalad shift in blood volume. The purpose of this study was to determine the effect of head-out water immersion on the cardiorespiratory response to graded dynamic exercise. Nineteen healthy middle-aged men performed upright cycling exercise at 40, 60 and 80% of maximal oxygen consumption on land and in water (31.0 +/- 1.0 degrees C) to the shoulders. Cardiac output (measured by the carbon dioxide rebreathing technique) was significantly greater in water at 40 and 80% maximal oxygen consumption. Stroke volume was significantly elevated at all stages of exercise. Heart rate did not differ significantly at 40 and 60% maximal oxygen consumption but was significantly lower in water at 80% maximal oxygen consumption. Total ventilation did not differ significantly in water and on land at any stage of exercise. The results suggest that the central redistribution of blood volume with head-out water immersion leads to an increase in stroke volume. Because there is not a proportional decrease in heart rate with the elevated stroke volume, cardiac output is regulated at a higher level during upright exercise in water compared with that on land. In conclusion, there are serious limitations of available, prerecorded rhythm data bases for designing and testing of automatic external defibrillators. Performance can be adequately assessed only by extensive clinical tests, which seem mandatory for this new and important type of defibrillator.

Long-term weight fluctuation and non-insulin-dependent diabetes mellitus in white women.

The association of long-term weight fluctuation with non-insulin-dependent diabetes mellitus (NIDDM) was investigated for a population of 8232 white female members of the Taking Off Pounds Sensibly (TOPS) weight-awareness program, between the ages of 40 and 50 years. An index of weight fluctuation was developed using current weight, weight at the time maximum height was reached, and recalled maximum and minimum weights for the third and fourth decades for each member of the study population. A logistic regression of diabetes prevalence as a function of weight fluctuation, waist-hip ratio, relative weight, and family history index showed standardized odds ratios of 1.10, 1.22, 1.19, and 1.06, respectively. The results suggest that the magnitude of long-term weight fluctuation is associated with the development of NIDDM.

Meta-analysis in cancer epidemiology.

Meta-analysis has seen increasing use as a tool in epidemiology over the past five years. Although this method is relatively well accepted for use in clinical trials, its use has proved somewhat more controversial in epidemiology. If meta-analysis is viewed as an evolutionary improvement over the review article, it may become more widely acceptable. Meta-analysis should incorporate the concern for study quality and differences in study design seen in classic review articles with the concern for rigor, objectivity, and quantitative precision characteristic of meta-analysis. Available tools for consideration of differences among studies are described with several examples from the literature. The extent to which various methods are used in published meta-analyses is described. Methods for assessing publication bias, and tools for combining dose-response data, are discussed also. Evaluation of risk factors and protective factors for cancer must be based on the weight of the evidence. Tools such as meta-analysis are essential if we are to interpret the vast number of completed studies in cancer epidemiology.

Drinking water and cancer.

Any and all chemicals generated by human activity can and will find their way into water supplies. The types and quantities of carcinogens present in drinking water at the point of consumption will differ depending on whether they result from contamination of the source water, arise as a consequence of treatment processes, or enter as the water is conveyed to the user. Source-water contaminants of concern include arsenic, asbestos, radon, agricultural chemicals, and hazardous waste. Of these, the strongest evidence for a cancer risk involves arsenic, which is linked to cancers of the liver, lung, bladder, and kidney. The use of chlorine for water treatment to reduce the risk of infectious disease may account for a substantial portion of the cancer risk associated with drinking water. The by-products of chlorination are associated with increased risk of bladder and rectal cancer, possibly accounting for 5000 cases of bladder cancer and 8000 cases of rectal cancer per year in the United States. Fluoridation of water has received great scrutiny but appears to pose little or no cancer risk. Further research is needed to identify and quantify risks posed by contaminants from drinking-water distribution pipes, linings, joints, and fixtures and by biologically active micropollutants, such as microbial agents. We need more cost-effective methods for monitoring drinking-water quality and further research on interventions to minimize cancer risks from drinking water.

Airborne particulates and hospital admissions for cardiovascular disease: a quantitative review of the evidence.

This is a quantitative review of studies characterizing the relationship between exposure to airborne particulates and hospital admissions for cardiovascular disease. A MEDLINE search and a review of reference lists were conducted to identify time-series studies that considered particles less than 10 microm or 2.5 microm in diameter (PM(10) and PM(2.5), respectively) and their association with day-to-day variation in cardiovascular admissions. The results of these studies were standardized to give estimates of the percentage increase in hospital admissions associated with an increase in ingestion of ambient particles of 10 microg/m3. The results were grouped and compared on the basis of the specific outcomes and exposure measures. When studies that considered the association between PM(10) exposure and specific cardiovascular outcomes were pooled (after exclusion of outliers), a 10-microg/m(3) increase in PM(10) was associated with increases in admission rates of 0.8% (95% confidence interval [CI]: 0.5, 1.2%) for congestive heart failure, 0.7% (95% CI: 0.4, 1.0%) for ischemic heart disease, and 0.2% (95% CI: -0.2, 0.6%) for cerebrovascular accidents. These effects tended to diminish substantially when gaseous co-pollutants were considered. The extent to which these effects are due to fine particles is unclear. The available studies indicate that exposure to airborne particles is associated with hospital admissions for cardiovascular disease; but the magnitude of this effect depends strongly on the specific disease category being considered, the time lag used in the analysis, and the type and amount of co-pollutants. Future studies should include careful consideration of the role of co-pollutants in this association, the interaction of particles with temperature, the impact of particle size on this effect, and the extent to which the observed effect involves short-term "harvesting."

Carbon monoxide and hospital admissions for congestive heart failure: evidence of an increased effect at low temperatures.

The combined effects of carbon monoxide and low temperature on daily variation in hospital admissions for congestive heart failure (CHF) were examined for a 4-year period in Chicago, Illinois. Medicare hospital admissions for CHF were analyzed as a function of the maximum hourly temperature, maximum hourly levels of carbon monoxide (CO), and other criteria pollutants in Chicago for each day of the 4-year period (1986-1989). The regression analyses for the time series were conducted using single and multipollutant models with interaction terms and adjustments for weather, weekly cycles, seasonal effects, and secular trend. The data were also grouped into three temperature ranges, <40 degrees, 40 degrees-75 degrees, and >75 degrees F, and the relationship between CO and CHF admissions was evaluated for each range. For the 4-year time series, the CO level was positively associated with hospital admissions for CHF in the single pollutant and multipollutant models after adjustment for seasonal effects and weather pattern. The relative risks of hospital admissions for CHF in Chicago associated with the 75th percentile of exposure to CO in the high, medium, and low temperature ranges were 1.02 [95% confidence interval (CI), 0.95-1.10], 1.09 (CI, 1.04-1.14), and 1.15 (CI, 1.09-1.22), respectively. In these data, the effect of CO on hospital admissions for CHF was temperature dependent, with the magnitude of the effect increasing with decreasing temperature. This synergy may help to explain the association between ambient CO and CHF admissions demonstrated in other studies.

Geographic variability in hospital admission rates for respiratory disease among the elderly in the United States.

BACKGROUND: The elderly represent a susceptible subpopulation that experiences disproportionate levels of morbidity and mortality from respiratory disease. As a consequence, they are frequently hospitalized for these conditions. Evaluating the geographic distributions of these hospital admissions can provide useful insights concerning patterns in incidence and medical care for respiratory diseases. METHODS: All hospital admissions for pneumonia, acute respiratory infections, asthma, and chronic obstructive pulmonary disease from the United States for a 6-year period (1984 through 1989) were identified using Medicare admissions records. Age-, race-, and sex-standardized annual admission rates were calculated for each county and spatial clustering of disease specific rates was evaluated using Moran's I statistic. Ecologic analyses were conducted using multiple regression procedures with county-specific measures of average annual temperature, average income, household crowding, median educational level, population density, physicians per capita, and hospital beds per capita together with surrogate measures of cigarette consumption and occupational exposures as predictor variables. RESULTS: Hospital admission rates in the elderly for all four categories of respiratory disease showed marked regional elevations (p < 0.0001), particularly in the southeast and the northern plains states. Low median education level, low per capita income, and household crowding were all associated with elevated hospital admission rates. Surrogate measures of cigarette consumption were strongly associated with hospital admissions in all four disease groups. Hospital beds per capita demonstrated positive associations with hospital admissions, but the number of physicians per capita exhibited consistent inverse relationships with hospital admissions. CONCLUSIONS: Hospital admission rates for respiratory diseases among the elderly show marked geographic variation and are associated with regional indicators of socioeconomic status, availability of medical resources, occupational lung disease rates, and smoking.

Evidence for asymmetrical hemispheric priming using known and unknown warning stimuli in two language-trained chimpanzees (Pan troglodytes).

In this article results are reported from 3 warning stimulus-priming experiments that assessed hemisphere-specific activation and lateralization in 2 language-trained chimpanzees (Pan troglodytes). Results from Experiment 1 indicated a right visual field advantage in priming for meaningful warning stimuli presented in blocks of 36 trials. In Experiments 2 and 3, randomized presentations of meaningful, familiar, and meaningless stimuli resulted in right visual field advantages for meaningful warning stimuli. No visual half-field differences were found for familiar or meaningless warning stimuli. The findings are similar to those found in human subjects using known-unknown symbol paradigms; they suggest that basic phylogenetic neuropsychological systems related to activation and priming processes may link nonhuman primate and human studies of lateralization.

Laterality for visual-spatial processing in two language-trained chimpanzees (Pan troglodytes).

Most reviews of laterality in nonhuman primates indicate that hemispheric asymmetries, similar to those found in humans, are not evident. With the growing evidence for cognitive processes germane to language in apes, in addition to their phylogenetic similarity to humans, they appear to be useful candidates for studies of laterality. Laterality for visual-spatial processing in two language-trained chimpanzees (Pan troglodytes) was investigated with a visual half-field paradigm. Initially, the chimpanzees were taught to manipulate a joystick that controlled the movement of a cursor on a computer monitor to a central fixation point. Subjects were then taught a visual discrimination based on the location of a short line contained within a geometric form. Testing consisted of systematic presentation rates of 15, 122, and 226 ms to the left and right visual fields. For half of the trials, subjects used their left hand to respond and, alternately, used the right hand for the remaining trials. Accuracy and reaction time were the dependent measures. One subject demonstrated significantly faster reaction times to stimuli presented to the left visual field (LVF) regardless of which hand was used to respond. The other subject demonstrated a significant LVF bias when using the left hand to respond. The results are discussed in the context of current theories on the evolution of laterality and its relation to linguistic functioning.

Hemispheric priming by meaningful and nonmeaningful symbols in language-trained chimpanzees (Pan troglodytes): further evidence of a left hemisphere advantage.

Hemispheric priming was examined in 3 language-trained chimpanzees (Pan troglodytes) using a simple reaction time paradigm. Subjects were required to hold down a response button until the occurrence of a response cue. A warning stimulus was presented to either the left visual field (LVF) or the right visual field (RVF) before the response cue occurred. No warning stimulus was presented on control trials. The warning stimuli were geometric communicative symbols from two semantic categories: foods and tools. A third set of warning stimuli were familiar geometric symbols. Dependent measures included reaction time and the number of false-positive responses. Reaction-time data indicated an RVF advantage in priming when the warning stimuli were food or tool symbols. No significant visual half-field differences were found for familiar symbols, but a trend toward an RVF advantage was observed. These effects were enhanced when subjects responded with their left hand. False-positive data also indicated an RVF advantage for the food and tool warning stimuli. The data indicate that hemispheric asymmetries for processing communicative symbols are present in language-trained chimpanzees.

Cardiovascular regulation during head-out water immersion exercise.

Head-out water immersion is known to increase cardiac filling pressure and volume in humans at rest. The purpose of the present study was to assess whether these alterations persist during dynamic exercise. Ten men performed upright cycling exercise on land and in water to the suprasternal notch at work loads corresponding to 40, 60, 80, and 100% maximal O2 consumption (VO2max). A Swan-Ganz catheter was used to measure right atrial pressure (PAP), pulmonary arterial pressure (PAP), and cardiac index (CI). Left ventricular end-diastolic (LVED) and end-systolic (LVES) volume indexes were assessed with echocardiography. VO2max did not differ between land and water. RAP, PAP, CI, stroke index, and LVED and LVES volume indexes were significantly greater (P less than 0.05) during exercise in water than on land. Stroke index did not change significantly from rest to exercise in water but increased (P less than 0.05) on land. Arterial systolic blood pressure did not differ between land and water at rest or during exercise. Heart rates were significantly lower (P less than 0.05) in water only during the two highest work intensities. The results indicate that indexes of cardiac preload are greater during exercise in water than on land.

Serum dioxin and cognitive functioning among veterans of Operation Ranch Hand.

We used the Halstead-Reitan neuropsychological test battery, the Wechsler adult intelligence scale-revised, the Wechsler memory scale, and the wide range achievement test to assess cognitive functioning among Air Force veterans exposed to Agent Orange and its contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin), during the Vietnam war The index subjects were veterans of Operation Ranch Hand (N = 937), the unit responsible for aerial herbicide spraying in Vietnam from 1962 to 1971. A comparison group of other Air Force veterans (N= 1,052), who served in Southeast Asia during the same period but were not involved with spraying herbicides served as referents. Cognitive functioning was assessed in 1982, and dioxin levels were measured in 1987 and 1992. We assigned each Ranch Hand veteran to the background, low, or high dioxin exposure category on the basis of a measurement of dioxin body burden. Although we found no global effect of dioxin exposure on cognitive functioning, we did find that several measures of memory functioning were decreased among veterans with the highest dioxin exposure. These results became more distinct when we restricted the analysis to enlisted personnel, the subgroup with the highest dioxin levels. An analysis based on dioxin quintiles in the combined cohort produced consistent results, with veterans in the fifth quintile exhibiting reduced verbal memory function. Although statistically significant, these differences were relatively small and of uncertain clinical significance.

The conservation of redundancy in genetic systems: effects of sexual and asexual reproduction.

The relationship between probability of survival and the number of deleterious mutations in the genome is investigated using three different models of highly redundant systems that interact with a threatening environment. Model one is a system that counters a potentially lethal infection; it has multiple identical components that act in sequence and in parallel. Model two has many different overlapping components that provide threefold coverage of a large number of vital functions. The third model is based on statistical decision theory: an ideal detector, following an optimum decision strategy, makes crucial decisions in an uncertain world. The probability of a fatal error is reduced by a redundant sampling system, but the chance of error rises as the system is impaired by deleterious mutations. In all three cases the survival profile shows a synergistic pattern in that the probability of survival falls slowly and then more rapidly. This is different than the multiplicative or independent survival profile that is often used in mathematical models. It is suggested that a synergistic profile is a property of redundant systems. Model one is then used to study the conservation of redundancy during sexual and asexual reproduction. A unicellular haploid organism reproducing asexually retains redundancy when the mutation rate is very low (0.001 per cell division), but tends to lose high levels of redundancy if the mutation rate is increased (0.01 to 0.1 per cell division). If a similar unicellular haploid organism has a sexual phase then redundancy is retained for mutation rates between 0.001 and 0.1 per cell division. The sexual organism outgrows the asexual organism when the above mutation rates apply. If they compete for finite resources the asexual organism will be extinguished. Variants of the sexual organism with increased redundancy will outgrow those with lower levels of redundancy and the sexual process facilitates the evolution of more complex forms. There is a limit to the extent that complexity can be increased by increasing the size of the genome and in asexual organisms this leads to progressive accumulation of mutations with loss of redundancy and eventual extinction. If complexity is increased by using genes in new combinations, the asexual form can reach a stable equilibrium, although it is associated with some loss of redundancy. The sexual form, by comparison, can survive, with retention of redundancy, even if the mutation rate is above one per generation. The conservation and evolution of redundancy, which is essential for complexity, depends on the sexual process of reproduction.

Sexual selection, redundancy and survival of the most beautiful.

A model is described of a highly redundant complex organism that has overlapping banks of genes such that each vital function is specified by several different genetic systems. This generates a synergistic profile linking probability of survival to the number of deleterious mutations in the genome. Computer models show that there is a dynamic interaction between the mean number of new deleterious mutations per generation (X), the mean number of deleterious mutations in the genome of the population (Y) and percentage zygote survival (Zs). Increased X leads to increased Y and a fall in Zs but it takes several generations before a new equilibrium is reached. If sexual attraction is influenced by the number of deleterious mutations in the genome of individuals then Y is reduced and Zs increased for any given value of X. This fall in Y and rise in Zs is more marked in polygamous than monogamous mating systems. The model is specified such that deleterious mutations can occur without any observable or measurable effect on function. Thus sexual selection, in this organism, for low levels of deleterious mutations cannot be based on assessment of performance. Instead it is based on a simple symmetrical surface pattern that is flawlessly reproduced by organisms with no deleterious mutations, but is less than perfect, and therefore less attractive, if genetic systems have been deleted. A complex vital task requires a system with a high level of redundancy that acts so that the loss of one component has no observable effect and therefore cannot be used for sexual selection. The reproduction of a beautiful surface pattern also requires a low error, high redundancy genetic system; however, in this case there is advantage if a single deleterious mutation produces a recognisable change. This leads to the conclusion that sexual selection and sexual attraction should be based on beauty rather than utility, and explains the common observation in nature that it is the most beautiful that survive.

NES test performance in a large US Army veteran sample: relationships with both demographic factors and traditional neuropsychological measures.

A large sample of Vietnam-era US Army veterans completed a set of 16 neuropsychological tests, including six computer-based tests from the Neurobehavioral Evaluation System (NES), during medical examinations supervised by the US Centers for Disease Control (CDC). Data for 881 participants of the Agent Orange Validation Study (AOV) and Vietnam Experience Study (VES) were available for analysis from public access data tapes provided by CDC. Information was available for several potential covariates from demographic questionnaires, a medical examination, and a medical history. Explorator, principal components factor analysis of 16 test variables yielded four factors, including one on which most of the NES tests loaded. The single best predictor of most neuropsychological performance variables was an index of general intellectual level as measured at entry into the Army almost 20 years before the neuropsychological examinations. Alcohol drinking variables were not related to neuropsychological performance. Several measures of general intelligence were compared for use as covariates of neuropsychological test performance. All were superior to years of education in statistically controlling for general intellectual level.

Travel behavior of nursing home residents perceived as wanderers and nonwanderers.

A video-based observational methodology was used to assess the travel behaviors of 40 nursing home residents, 24 of whom were identified by nursing staff as wanderers. Travel was monitored continuously for 30 days, resulting in the recording of over 5,000 unassisted travel events. Four basic travel patterns were observed: direct travel (86.8%), lapping (11.6%), random travel (.9%), and pacing (.7%). Travel efficiency (percentage of direct travel) was significantly related to cognitive status (r = .56), with inefficient travel most prevalent in severely demented participants.

Quantum adiabatic optimization and combinatorial landscapes.

In this paper we analyze the performance of the Quantum Adiabatic Evolution algorithm on a variant of the satisfiability problem for an ensemble of random graphs parametrized by the ratio of clauses to variables, gamma=M/N . We introduce a set of macroscopic parameters (landscapes) and put forward an ansatz of universality for random bit flips. We then formulate the problem of finding the smallest eigenvalue and the excitation gap as a statistical mechanics problem. We use the so-called annealing approximation with a refinement that a finite set of macroscopic variables (instead of only energy) is used, and are able to show the existence of a dynamic threshold gamma= gamma(d) starting with some value of K -the number of variables in each clause. Beyond the dynamic threshold, the algorithm should take an exponentially long time to find a solution. We compare the results for extended and simplified sets of landscapes and provide numerical evidence in support of our universality ansatz. We have been able to map the ensemble of random graphs onto another ensemble with fluctuations significantly reduced. This enabled us to obtain tight upper bounds on the satisfiability transition and to recompute the dynamical transition using the extended set of landscapes.

Childhood asthma surveillance using computerized billing records: a pilot study.

OBJECTIVE: This paper describes a pilot project to develop and implement a low-cost system for ongoing surveillance of childhood asthma in Milwaukee County, Wisconsin. METHODS: The authors organized a planning workshop to solicit information and ideas for an asthma surveillance system, bringing together national experts with Milwaukee professionals and community representatives involved in the prevention and treatment of asthma. Based on recommendations from the workshop, a pilot surveillance project was implemented in Milwaukee County using records of emergency room visits and hospital admissions for asthma abstracted from the computerized billing records of the Children's Hospital of Wisconsin (CHW), retrospectively for 1993 and prospectively for 1994. Retrospective data were also sought from the other hospital emergency departments in Milwaukee County to evaluate the representativeness of the CHW data. Surveillance data were used to evaluate utilization of care by patient subgroups and to describe temporal patterns in emergency room visits. RESULTS: Of the emergency department visits for asthma in Milwaukee County in 1993, CHW accounted for 94% among infants less than 1 year of age, 89% among children ages 1 through 5 years, and only 59% among children between the ages of 6 and 18 years. In 1994, the 7% of asthmatic children with repeat hospital admissions accounted for 38% of all hospital admissions for asthma and the 20% with repeat emergency department visits accounted for 50% of all emergency visits. Emergency visits for asthma showed clear seasonality, with a peak in the fall and a smaller peak in the spring. CONCLUSIONS: Computerized medical billing data provide an opportunity for asthma surveillance at a relatively low cost. The data obtained are useful for tracking trends in exacerbations of asthma and the use of medical services for asthma care and should prove valuable in targeting interventions.