Low-risk Sites Research Articles

Modeling natural attenuation of benzene with analytical and numerical models

Natural attenuation of benzene is a much-accepted technology for remediating low risk sites. To date, numerous protocols have been developed for assessing natural attenuation and measuring indicator parameters. Many models have additionally been developed to describe the advection, dispersion, sorption and biodegradation processes involved. It is evident that while there is extensive guidance in natural attenuation protocols for field sampling methodologies, less emphasis is placed on analyzing natural attenuation data for supporting appropriate model development. This paper presents methodologies for data analysis and interpretation that may be undertaken to achieve data reduction for modeling purposes. A case study is presented to illustrate the use of an analytical and a numerical natural attenuation model at the same site for predicting the time required to achieve the remedial goal at the site.

Interventions for basal cell carcinoma of the skin: systematic review

Objectives To assess the effects of treatments for basal cell carcinoma.Methods Systematic review of randomised controlled trials.Main outcome measure Recurrence of basal cell carcinoma at three years or beyond, assessed...

Dispositional Trust and Distrust Distinctions in Predicting High- and Low-Risk Internet Expert Advice Site Perceptions

This study examines whether some types of dispositional trust/distrust concepts are better than other types at inducing consumers to trust a Web advice provider. We propose and test a model in which dispositional trust and distrust concepts are given separate roles. This unique approach is based on the growing, but untested theoretical consensus that trust and distrust are separate concepts that co-exist yet differ in terms of their emotional makeup. While trust concepts tend to be calm and collected, distrust concepts embody significant levels of fear and insecurity. Based on this difference, we propose that dispositional distrust concepts will be better predictors of high-risk Internet legal advice site perceptions, while the corresponding trust concepts will be better predictors of low-risk Internet legal advice site perceptions. As proposed, the study finds that dispositional trust better predicts low-risk perceptions, while dispositional distrust better predicts high-risk perceptions. For e-commerce advice site research, the findings of

Dispositional Trust And Distrust Distinctions in Predicting High- and Low-Risk Internet Expert Advice Site Perceptions

This study examines whether some types of dispositional trust/distrust concepts are better than other types at inducing consumers to trust a Web advice provider. We propose and test a model in which dispositional trust and distrust concepts are given separate roles. This unique approach is based on the growing, but untested theoretical consensus that trust and distrust are separate concepts that co-exist yet differ in terms of their emotional makeup. While trust concepts tend to be calm and collected, distrust concepts embody significant levels of fear and insecurity. Based on this difference, we propose that dispositional distrust concepts will be better predictors of high-risk Internet legal advice site perceptions, while the corresponding trust concepts will be better predictors of low-risk Internet legal advice site perceptions. As proposed, the study finds that dispositional trust better predicts low-risk perceptions, while dispositional distrust better predicts high-risk perceptions. For e-commerce advice site research, the findings of this article suggest that perhaps scholars should Not only study dispositional trust but also dispositional distrust.

Wolf reintroduction, predation risk, and cottonwood recovery in Yellowstone National Park

We studied young riparian cottonwoods ( Populus spp.) and associated woody plants along Soda Butte Creek and the Lamar River in northeastern Yellowstone National Park (YNP) to examine the potential influence of wolf/elk interactions upon plant growth. After a period of approximately 70 years without wolves in YNP, they were reintroduced in the winter of 1995–1996. When we compared woody plant heights shown in photographs taken prior to 1998 with those shown in 2001–2002 photos, we found an increase in the height of riparian woody plants for six of the eight sites within the study area. Plants were tallest (1–4 m) at point bar, stream confluence, and island sites, while heights remained relatively low (<1 m) along straight river reaches in a wide valley setting. We measured differences in both browsing intensity and cottonwood height for sites with relatively high predation risk (low visibility and/or the presence of escape barriers) and compared them to nearby sites with relatively low predation risk (open areas). In general, the high-risk sites had lower browsing intensities (percent of stems browsed) and taller plants than low-risk sites. Although the young cottonwoods on high-risk sites were growing taller each year over the last 4 years, there was little change in the plant heights for low-risk sites. For a stand of young cottonwoods growing adjacent to a gully (potential escape barrier), we found a linear correlation ( r 2=0.76) between cottonwood height and adjacent gully depth; as gully depth increased, the percent of stems browsed decreased and cottonwood height increased. While the release of cottonwood and willows within the study area is in a very early stage, results provide rare empirical evidence illustrating the indirect effects of a top carnivore in a terrestrial food chain and supports theories on: (1) predation risk effects and (2) trophic cascades (top-down control). Wolf reintroductions into the Yellowstone environment may thus represent a management action that was needed to help insure the restoration of riparian species and preservation of biodiversity.

Satellite imagery characterizes local animal reservoir populations of Sin Nombre virus in the southwestern United States.

The relationship between the risk of hantaviral pulmonary syndrome (HPS), as estimated from satellite imagery, and local rodent populations was examined. HPS risk, predicted before rodent sampling, was highly associated with the abundance of Peromyscus maniculatus, the reservoir of Sin Nombre virus (SNV). P. maniculatus were common in high-risk sites, and populations in high-risk areas were skewed toward adult males, the subclass most frequently infected with SNV. In the year after an El Niño Southern Oscillation (ENSO), captures of P. maniculatus increased only in high-risk areas. During 1998, few sites had infected mice, but by 1999, 1820 of the high-risk sites contained infected mice and the crude prevalence was 30.8%. Only 118 of the low-risk sites contained infected rodents, and the prevalence of infection was lower (8.3%). Satellite imagery identified environmental features associated with SNV transmission within its reservoir population, but at least 2 years of high-risk conditions were needed for SNV to reach high prevalence. Areas with persistently high-risk environmental conditions may serve as refugia for the survival of SNV in local mouse populations.

Screening of Tanzanian women of childbearing age for urinary schistosomiasis: validity of urine reagent strip readings and self-reported symptoms.

The screening of women of childbearing age for haematuria, leukocyturia and proteinuria to detect urinary schistosomiasis can be confounded by several factors such as menstruation, pregnancy and genitourinary infections. We therefore undertook a study in an area endemic for Schistosoma haematobium in the United Republic of Tanzania to carry out the following: assess the sensitivity, specificity and predictive values--in women of childbearing age--of indirect indicators of urinary schistosomiasis, as measured by urine reagent strip readings; assess the predictive values of self-reported symptoms; and finally to estimate the morbidity attributable to S. haematobium. A total of 303 women (128 and 175, respectively, living in high- and low-risk sites) participated in the study. Haematuria was more frequent among women excreting S. haematobium eggs than among those who did not (65% versus 32%). The predictive potential of all indirect disease markers was poor in the highly endemic site, while in the sites with low endemicity the negative predictive values were high. Among infected women, 54% of haematuria could be attributed to S. haematobium, but for patients with more than 10 eggs/10 ml the attributable fraction rose to 70%. Symptoms of "bloody urine" and "pain while urinating" were recalled significantly more often by women living in the highly endemic site. On a population level, one-third of the self-reported cases with bloody urine could be attributed to urinary schistosomiasis. Screening of women of childbearing age for urinary schistosomiasis using urine reagent strips can be biased in two directions. The prevalence of S. haematobium will be overestimated if other causes of haematuria, such as reproductive tract infections, are highly endemic. On the other hand, women with light or very light infections will be missed and will not be treated. This is of concern because genital schistosomiasis, a possible risk factor for the transmission of HIV, occurs among women even with light infections.

Geographic variation in sperm production by Trinidadian guppies

Population comparisons yield important insights into adaptive differentiation. However, despite the current interest in sperm competition and spermatogenesis, geographic variation in these traits has received little attention. We tested the hypothesis that sperm production covaries with risk by comparing five natural populations of Trinidadian guppies (Poecilia reticulata): two that inhabited dangerous Crenicichla localities, two from low-risk Rivulus sites and a 'transplant' population comprised of the descendants of guppies moved from one of the high-risk sites to a low-predation environment. As predicted, males from the three low-risk sites performed significantly more courtship displays and had larger sperm reserves than their high-risk counterparts. This result implies higher rates of sperm competition in the low-risk sites.

Elective neck irradiation versus observation of the clinically negative neck of patients with oral cancer

Purposes: A retrospective study was conducted to determine the efficacy of elective neck irradiation (ENI) versus observation of patients with oral tumors of varying T stages and clinically negative necks, and to statistically evaluate outcome in the two groups with regard to the subsequent development of neck disease. Patients and Methods: Seventy-three patients were treated with surgery of their primary site; 31 received ENI, and 42 of the necks were observed. Of the ENI patients, 3.2% developed neck disease compared with 31% of those observed. When the two groups were evaluated by the T stage of the primary tumor, the results for ENI versus observation were as follows: T1 (0% vs 31 %), T2 (5.9% vs 26.7%), T3 + 4 (0% vs 31%), respectively ( P < .0000, adjusted odds ratio = 13.73, 95% confidence interval). The difference between the two groups was highly statistically significant. One hundred fourteen patients were treated with only radiation therapy alone at the primary site. In this group, 88 received ENI, and 16 necks were observed. Eight percent of the ENI group developed neck disease, compared with 3.8% of the observational group. Further evaluation by T stage of ENI versus observation showed T1 (3% vs 0%); T2 (9.3% vs 7.7%); T3 + 4 (5.6% vs 0%), respectively. The difference between these groups was not found to be statistically significant. Results: The 5-year disease-free survival rate for the surgical group was 90% for patients who received ENI and 40% for those observed. This difference was statistically significant ( P = .0007). No statistical difference was found in 5-year disease-free survival for the radiation group between ENI and observation. Conclusions: When comparing the above data for ENI versus observation, the survival advantages of elective neck irradiation in patients whose primary tumor was treated surgically is striking for all T stages. These results make the decision to observe the neck in such patients difficult to justify. Lack of statistical difference between ENI and observation in the radiation cohort likely reflects selection bias. If radiation therapy is being used to treat the primary disease, only low-risk sites or histologically favorable tumors would not, on a routine basis, have the neck fields treated as well.

Sexual conflict as a consequence of ecology: evidence from guppy, Poecilia reticulata , populations in Trinidad

An investigation of the behaviour of guppies, Poecilia reticulata, in the wild reveals that sexual conflict varies markedly in different habitats. Males from high-predation sites in Trinidad (where the pike cichlid Crenicichla alta occurs) engage in less antipredator behaviour than females, have lower foraging rates than males from low-risk sites and are able to devote a greater proportion of their time to pursuing females and attempting sneaky matings. As a result, females in such locations receive approximately one sneaky mating attempt per minute. Female behaviour in high-predation sites is thus constrained not only by their own predator avoidance but also by sexual harassment which is itself an indirect consequence of risk. Sexual harassment is likely to compromise female choice and may have significant evolutionary consequences.

Inherited Population Differences in Avoidance Conditioning in Three-Spined Sticklebacks, Gasterosteus Aculeatus

Laboratory-reared predator-naive three-spined sticklebacks from two sites, one with abundant predatory fish (the high-risk site) and the other essentially predator-free (the low-risk site), were given a passive avoidance conditioning task in which they received a simulated attack from a model avian predator whenever they entered a previously-favoured feeding patch. 15/16 fish learned to avoid the dangerous patch within 15 days, but those from the high-risk site did so significantly faster and received fewer attacks in the process. The two categories of fish did not differ either in active avoidance of the attack stimulus or in the rate at which they started to re-exploit the dangerous patch once negative reinforcement ceased. It is argued that fish from high- and low-risk sites differ in the negatively reinforcing properties of the same, standardised attack.

Recurrence Rates of Treated Basal Cell Carcinomas: Part 2: Curettage‐Electrodesiccation

This is the second article in a series that reviews the experience in the Skin and Cancer Unit, from 1955 through 1982, with the treatment of basal cell carcinomas (BCCs). This report deals with 2314 previously untreated (primary) BCCs removed by curettage-electrodesiccation. Multivariate analysis showed that increasing lesion diameter (P less than .001), high-risk anatomic sites (nose, paranasal, nasal-labial groove, ear, chin, mandibular, peri-oral, and peri-ocular areas) (P less than .001), middle-risk anatomical sites (scalp, forehead, pre- and post-auricular, and malar areas) (P less than .001), and time-span treated (1955 to 1963) (P = .012) were independent risk factors for high recurrence rates. The patient's age, sex, and lesion duration before treatment did not affect the recurrence rates. In order to best illustrate our current experience with BCCs, the last time-span (1973 to 1982) was examined in detail. For the low-risk sites (neck, trunk, and four extremities), BCCs of all diameters responded well to curettage-electrodesiccation with an overall 5-year recurrence rate of 3.3% (SE = 1.5%) determined by the modified life-table method. In the middle-risk sites BCCs less than 10 mm in diameter had a recurrence rate of 5.3% (SE = 2.7%). Finally, in the high-risk sites, lesions less than 6 mm in diameter had a recurrence rate of 4.5% (SE = 2.6%). Thus, BCCs less than 6 mm in diameter, regardless of anatomic site, as well as selected larger BCCs depending on their anatomic site, are effectively treated by currettage-electrodesiccation.

Flexible responses to predators in a marine fish

The effect of predators on the behavior of signal blennies, Emblemaria hypacanthus (Pisces Chaenopsidae), was examined by comparing populations from two sites in the central Gulf of California that differed significantly in the abundance of predatory fishes. At the low-risk site the sexes differed in habitat use with males and females spending most of their time in shelters and in the open, respectively. At the high-risk site both sexes spent most of their time in shelters and also moved less and retreated into shelters more frequently than they did at the low-risk site. Both sexes fed at similar rates at the two sites, but their feeding efficiency was not measured. Males at the high-risk site courted females less vigorously and exhibited less intense courtship coloration than did males at the low-risk site. Although this difference in coloration was evident in the field over 3 consecutive years, males from both sites exhibited full courtship coloration in aquaria lacking predators. This implies that the ...

Plume management—An inexpensive long-term strategy for groundwater contamination at low-risk sites

The costs of full-scale groundwater treatment and source removal and the unrealistic goals of many groundwater treatment projects have prompted a reevaluation of long-term remediation strategies. This report has presented a plan that manages the groundwater contamination and is sensitive to the changing regulatory and technical climate. The groundwater treatment system is inexpensive to install, operate, and maintain. Plume migration has been stopped. Treatment time is exceedingly long, but the site operator is now free to evaluate new technology or the development of a risk-based clean-up strategy. We believe that implementing such a strategy at low-risk sites can result in significant cost savings to the hazardous waste clean-up problem.

Applying Human Factors in Anesthesia Monitoring

The ergonomics of the anesthesia workstation have been examined, and a novel apparatus for monitoring depth of anesthesia has been developed. The depth measuring apparatus works by detecting esophageal motility during anesthesia and displaying the resulting data to the clinician. Esophageal activity is mediated by the vagus nerve and brain stem, and co-varies with the degree of brain stem activity, therefore it can be used to estimate depth of anesthesia. Moreover, the location and availability of the esophagus allow minimally-invasive monitoring of many other vital functions and the displaying of these functions on a single integrated monitor. This enables the clinician to derive from a single low-risk monitoring site a more comprehensive picture of the patient's physiological state. Data derived from clinical trials and research now underway in the UK and US tend to support these views. Now in its embryonic form, this research is being directed toward an integrated anesthesia monitor which will ultimately improve the ergonomics and economics of anesthesia delivery.

Predation risk and inter-population variation in antipredator behaviour in the three-spined stickleback, Gasterosteus aculeatus L.

Predation risk from fish and bird predators was assessed at seven Scottish Gasterosteus aculeatus L. sites. Samples of adult male and female sticklebacks and fry from each site were tested with either a model heron or a live pike to measure anti-predator responses. Principal Component Analyses were then used to describe the responses, the first factor to emerge from each multivariate analysis providing an index of overall level of response toward the predator. Significant sexual and inter-population differences in behaviour are described. Sticklebacks from populations at high risk from either predatory fish or birds showed higher fright response scores than fish from low risk sites. In general, adult male sticklebacks are bolder than adult females during interactions with predators.

Effect of Anatomical Location on Prognosis in Patients With Clinical Stage I Melanoma

A study of the influence of the anatomical location of malignant melanoma on the prognosis of 971 patients with stage I disease disclosed specific high-, intermediate-, and low-risk sites. High-risk sites included scalp, mandibular area, midline of trunk (anterior and posterior), upper medial thighs, hands, feet (except the arches), popliteal fossae, and genitalia. The life-table-adjusted five-year disease-free survival was 54% in the high-risk locations, 79% in intermediate-risk locations, and 93% in low-risk sites. A Cox proportional hazards analysis demonstrated that the grouping of lesions by their anatomical risk location had prognostic value that was significant in a model of eight other known predictive variables (thickness, sex, age, type, level, mitotic index, ulceration, and presence of preexistent nevus). The results indicate that anatomical location of the primary melanoma is significantly associated with five-year disease-free survival.

Preliminary analysis of meteorological and seasonal influences on crustal gas emission relevant to earthquake prediction

abstract The emission of gas from the Earth's crust is a complex process influenced by meteorological and seasonal parameters. The use of gas emission as a tool in earthquake prediction will require an understanding of these influences. Radon emanation has been integrated over weekly intervals and free mercury vapor emission over 212 hour intervals at a low seismic risk site in Colorado. Radon measured by the Track Etch® technique ranged from 136 to 1750 tracks/mm2 (81 to 1040 pC/liter) over the 1-yr period of the experiment. There was a strong correlation of radon emanation with: instrument vault temperature, barometric pressure, outside temperature, soil temperature, and whether or not the surface soil was frozen. Seasonal influences on radon emanation are important with 94 per cent of the variance being accounted for by the measured meteorological and seasonal parameters. Mercury concentrations in the instrument vault ranged from &amp;lt;1 to 53 ng/m3 over the 1 yr. Mercury emission correlates with vault temperature, vault relative humidity, outside temperature, barometric pressure, soil temperature and moisture, and the soil freeze-thaw cycle. Diurnal cycles are common but do not occur on all days. Other short-term noise in mercury emission is also important and phase shift or phase lag effects are important. Only 32 per cent of the variance in mercury emission can be accounted for by the measured meteorological and seasonal parameters. The short-term noise coupled with phase lags are important factors in mercury emission rates.