Effects of environmental factors on microbial induced calcium carbonate precipitation.

AIMS: To gain an understanding of the environmental factors that affect the growth of the bacterium Sporosarcina pasteurii, the metabolism of the bacterium and the calcium carbonate precipitation induced by this bacterium to optimally implement the biological treatment process, microbial induced calcium carbonate precipitation (MICP), in situ. METHODS AND RESULTS: Soil column and batch tests were used to assess the effect of likely subsurface environmental factors on the MICP treatment process. Microbial growth and mineral precipitation were evaluated in freshwater and seawater. Environmental conditions that may influence the ureolytic activity of the bacteria, such as ammonium concentration and oxygen availability, as well as the ureolytic activities of viable and lysed cells were assessed. Treatment formulation and injection rate, as well as soil particle characteristics are other factors that were evaluated for impact on uniform induction of cementation within the soils. CONCLUSIONS: The results of the study presented herein indicate that the biological treatment process is equally robust over a wide range of soil types, concentrations of ammonium chloride and salinities ranging from distilled water to full seawater; on the time scale of an hour, it is not diminished by the absence of oxygen or lysis of cells containing the urease enzyme. SIGNIFICANCE AND IMPACT OF STUDY: This study advances the biological treatment process MICP towards field implementation by addressing key environmental hurdles faced with during the upscaling process.

Vaginal creation for müllerian agenesis.

OBJECTIVE: The purpose of this study was to determine the effectiveness of passive vaginal dilation and McIndoe vaginoplasty in the creation of a neovagina for patients with müllerian agenesis. STUDY DESIGN: Fifty-one patients with Mayer-Rokitansky-Kuster-Hauser syndrome were treated for vaginal agenesis at either Johns Hopkins Hospital or Emory University. These historic prospective data were obtained by a review of medical records and a current office or telephone consultation. Initial office visits dated from November 18, 1983, through June 6, 1998. Their progress towards both anatomic and functional success was followed through August 1, 2000, which was a range of 2 to 16.8 years. One-way analysis of variance, Student t test, and logistic regression analysis were performed when appropriate. RESULTS: Four patients were lost to follow-up in various stages of the treatment. Ten patients refused vaginal dilation and proceeded to a successful modified McIndoe vaginoplasty. Of the 37 remaining patients, 91.9% anatomic and functional success was achieved from the Ingram method for vaginal dilation. Passive dilation failed in 8.1% of patients, who underwent a modified McIndoe vaginoplasty; all neovaginal creations were successful. All patients who underwent McIndoe vaginoplasty were compliant with postoperative vaginal form use. None of our patients lost vaginal space through contractions or loss of skin graft. Of those patients for whom dilation failed, only 1 patient discontinued the study because of bleeding and discomfort. In addition, only 1 patient from the 3 cases of failure had undergone a previous hymenotomy. Interestingly, 6 patients for whom dilation was successful (6/34 patients; 17.6%) had also undergone a previous hymenotomy. The mean follow-up time for all patients in this study was 111.1 +/- 7.2 months, with a range of 25 to 188 months. The mean follow-up time for those patients for whom dilation failed or who refused dilation was significantly lower at 64.5 +/- 9.5 and 65.3 +/- 18.5 months, respectively (P <.005). The mean time to successful dilation was 11.8 +/- 1.6 months with a range of 3 to 33 months. Although longer, no statistically significant difference was observed for dilation time in those patients for whom there was a failure to achieve anatomic or functional success (20.5 +/- 12.5 months; range, 8-33 months). CONCLUSION: These data reveal that passive dilation with the Ingram method is capable of creating an adequate vaginal canal in patients with vaginal agenesis, with respect to both function and anatomy even in those patients with a previous hymenotomy and resultant scar formation. Our modified McIndoe procedure has proved to be an excellent option for patients for whom conservative dilation techniques failed and who refuse to attempt any dilation. Interestingly, our data indicate that patients may now be trending toward immediate surgical correction rather than diligently using dilation techniques to create a vaginal space.

Co-occurrence of nutrition problems in Honduran children.

We used data from the 1996 Honduras National Micronutrient Survey to investigate the co-occurrence of vitamin A deficiency (VAD), anemia and stunting in a representative sample of Honduran children 1-5 y old. Observed frequencies of co-occurrence were compared with frequencies expected by chance in children 12-35.9 mo old (n = 633) and 36-59.9 mo old (n = 610) for the three possible two-way combinations of the problems and the three-way combination. Observed frequencies were greater than expected frequencies for all eight comparisons, and all comparisons except for that of stunting and anemia in younger children were significant. The observed frequency of the three-way co-occurrence was 8.4% compared with an expected co-occurrence of 8.1% in younger children (P: < 0.05) and 4.8% compared with 4.2%, respectively, in older children (P: < 0.001). Although there was statistical evidence for co-occurrence, differences between expected and observed prevalences were small for most comparisons. Our findings suggest that having one or two problems does not appreciably increase the probability of having another. The efficiency of nutrition interventions aimed at these conditions would not be improved by targeting children with any one of the conditions; rather, the three conditions should be treated as virtually independent when designing programs. Replication of this study in other settings is warranted.

Exposure efficacy and change in contact rates in evaluating prophylactic HIV vaccines in the field.

Field studies of the efficacy of prophylactic vaccines in reducing susceptibility rely on the assumption of equal exposure to infection in the vaccinated and unvaccinated groups. Differential exposure to infection could, however, be the goal of other types of intervention programme, or it could occur secondary to belief in the protective effects of a prophylactic measure, such as vaccination. We call this differential exposure the exposure efficacy, or behaviour efficacy. To study the relative contribution of unequal exposure to infection and differential susceptibility to the estimate of vaccine efficacy, we formulate a simple model that explicitly includes both susceptibility and exposure to infection. We illustrate this on the example of randomized field trials of prophylactic human immunodeficiency virus vaccines. Increased exposure to infection in the vaccinated group may bias the estimated reduction in susceptibility. The bias in the estimate depends on the choice of efficacy parameter, the amount of information used in the analysis, the distribution and level of protection in the population, and the imbalance in exposure to infection. Sufficient increase in contacts in the vaccinated could result in the vaccine being interpreted as having an immunosuppressive effect. Estimates of vaccine efficacy are generally more robust to imbalances in exposure to infection when the detailed history of exposure to infection can be used in the analysis or at high levels of protection. The bias also depends on the relationship between the distribution of vaccine protection and the distribution of behaviour change, which could differ between blinded and unblinded trials.

The relation of socioeconomic status to oral and pharyngeal cancer.

We assessed the relation between socioeconomic status and risk of oropharyngeal cancer in a population-based interview study of 762 male cases and 837 male controls in four areas of the United States. Three primary indicators of socioeconomic status were evaluated: education, occupational status, and percentage of potential working life spent in employment. With adjustment for the effects of established risk factors, such as use of tobacco products, alcohol consumption, and poor dentition, a relatively low percentage of years worked was also a risk factor. Educational attainment and occupational status were not independently related to risk of oropharyngeal cancer. These results are consistent with the hypothesis that behaviors that lead to social instability, and/or social instability itself, are linked to an increased risk of oral and pharyngeal cancers.

[Direct and indirect effects of vaccines: an annotation on the estimation of the vaccine efficacy from outbreaks caused by acute infection agents such as measles]. / Efectos directos e indirectos de las vacunas: una anotación sobre la estimación de la eficacia vacunal a partir de brotes por agentes de infecciones agudas como sarampión.

A good measure of the efficacy of vaccines should be based on an index that standardizes the exposure to infection of those who have been immunized and those who have not. In addition, the measure should not be influenced by indirect effects. In the case of outbreaks directly transmitted agents that cause acute infections diseases, the household secondary rates of attack are the best indicator of vaccine efficacy provided that the data are collected at the household level. If the data are not collected in this manner, the best indicator will be the estimated probability of transmission, even though this estimator and its meaning less obvious than the secondary attack of rate. Other strategies to estimate the efficacy of an immunization are more appropriate for situations that are more complex than outbreaks caused by acute infectious agents.