The supergene thorium and rare-earth element deposit at Morro do Ferro, Poços de Caldas, Minas Gerais, Brazil

The thorium and rare-earth element (Th-REE) deposit at Morro do Ferro formed under supergene lateritic weathering conditions. The ore body consists of shallow NW-SE elongated argillaceous lenses that extend from the top of the hill downwards along its south-eastern slope. The deposit is capped by a network of magnetite layers which protected the underlying highly weathered, argillaceous host rock from excessive erosion. The surrounding country rocks comprise a sequence of subvolcanic phonolite intrusions that have been strongly altered by hydrothermal and supergene processes. From petrological, mineralogical and geochemical studies, and mass balance calculations, it is inferred that the highly weathered host rock was originally carbonatitic in composition, initially enriched in Th and REEs compared to the surrounding silicate rocks. The intrusion of the carbonatite caused fenitic alteration in the surrounding phonolites, consisting of early potassic alteration followed by a vein-type Th-REE mineralization with associated fluorite, carbonate, pyrite and zircon. Subsequent weathering has completely decomposed the carbonatite forming a residual supergene enrichment of Th and REEs. Initial weathering of the carbonatite has created a chemical environment that might have been conductive to carbonate and phosphate complexing of the REEs in groundwaters. This may have appreciably restricted the dissolution of primary REE phases. Strongly oxidic weathering has resulted in a fractionation between Ce and the other light rare earth elements (LREEs). Ce3+ is oxidized to Ce4+ and retained together with Th by secondary mineral formation (cerianite, thorianite), and by adsorption on poorly crystalline iron- and aluminium-hydroxides. In contrast, the trivalent LREEs are retained to a lesser degree and are thus more available for secondary mineral formation (Nd-lanthanite) and adsorption at greater depths down the weathering column. Seasonally controlled fluctuations of recharge waters into the weathering column may help to explain the observed repetition of Th-Ce enriched zones underlain by trivalent LREE enriched zones.

Redox front geochemistry and weathering: theory with application to the Osamu Utsumi uranium mine, Poços de Caldas, Brazil

Numerical calculations describing weathering of the Poços de Caldas alkaline complex (Minas Gerais, Brazil) by infiltrating groundwater are carried out for time spans up to two million years in the absence of pyrite, and up to 500,000 years with pyrite present. Deposition of uranium resulting from infiltration of oxygenated, uranium bearing groundwater through the hydrothermally altered phonolitic host rock at the Osamu Utsumi uranium mine is also included in the latter calculation. The calculations are based on the quasi-stationary state approximation to mass conservation equations for pure advective transport. This approximation enables the prediction of solute concentrations, mineral abundances and porosity as functions of time and distance over geologic time spans. Mineral reactions are described by kinetic rate laws for both precipitation and dissolution. Homogeneous equilibrium is assumed to be maintained within the aqueous phase. No other constraints are imposed on the calculations other than the initial composition of the unaltered host rock and the composition of the inlet fluid, taken as rainwater modified by percolation through a soil zone. The results are in qualitative agreement with field observations at the Osamu Utsumi uranium mine. They predict a lateritic cover followed by a highly porous saprolitic zone, a zone of oxidized rock with pyrite replaced by iron-hydroxide, a sharp redox front at which uranium is deposited, and the reduced unweathered host rock. Uranium is deposited in a narrow zone located on the reduced side of the redox front in association with pyrite, in agreement with field observations. The calculations predict the formation of a broad dissolution front of primary kaolinite that penetrates deep into the host rock accompanied by the precipitation of secondary illite. Secondary kaolinite occurs in a saprolitic zone near the surface and in the vicinity of the redox front. Gibbsite forms a bi-modal distribution consisting of a maximum near the surface followed by a thin tongue extending downward into the weathered profile in agreement with field observations. The results are found to be insensitive to the kinetic rate constants used to describe mineral reactions.

Problem behavior of dementia patients predicts low-grade hypercoagulability in spousal caregivers

Low-grade hypercoagulability might be one pathway to explain how the chronic stress of dementia caregiving increases cardiovascular disease risk, but the specific aspects of caregiver stress that elicit hypercoagulability are elusive. We hypothesized that dementia patients' problem behaviors and negative reactions of caregivers to these behaviors would relate to hypercoagulability in caregivers.

A randomized trial of effects of health risk appraisal combined with group sessions or home visits on preventive behaviors in older adults

Background. To explore effects of a health risk appraisal for older people (HRA-O) program with reinforcement, we conducted a randomized controlled trial in 21 general practices in Hamburg, Germany. Methods. Overall, 2,580 older patients of 14 general practitioners trained in reinforcing recommendations related to HRA-O-identified risk factors were randomized into intervention (n = 878) and control (n = 1,702) groups. Patients (n = 746) of seven additional matched general practitioners who did not receive this training served as a comparison group. Patients allocated to the intervention group, and their general practitioners, received computer-tailored written recommendations, and patients were offered the choice between interdisciplinary group sessions (geriatrician, physiotherapist, social worker, and nutritionist) and home visits (nurse). Results. Among the intervention group, 580 (66%) persons made use of personal reinforcement (group sessions: 503 [87%], home visits: 77 [13%]). At 1-year follow-up, persons in the intervention group had higher use of preventive services (eg, influenza vaccinations, adjusted odds ratio 1.7; 95% confidence interval 1.4–2.1) and more favorable health behavior (eg, high fruit/fiber intake, odds ratio 2.0; 95% confidence interval 1.6–2.6), as compared with controls. Comparisons between intervention and comparison group data revealed similar effects, suggesting that physician training alone had no effect. Subgroup analyses indicated favorable effects for HRA-O with personal reinforcement, but not for HRA-O without reinforcement. Conclusions. HRA-O combined with physician training and personal reinforcement had favorable effects on preventive care use and health behavior.

Effect of Alzheimer caregiving stress and age on frailty markers interleukin-6, C-reactive protein, and D-dimer

BACKGROUND: Elevated plasma levels of interleukin (IL)-6, C-reactive protein (CRP), and D-dimer belong to the biological alterations of the "frailty syndrome," defining increased vulnerability for diseases and mortality with aging. We hypothesized that, compatible with premature frailty, chronic stress and age are related in predicting inflammation and coagulation activity in Alzheimer caregivers. METHODS: Plasma IL-6, CRP, and D-dimer levels were measured in 170 individuals (mean age 73 +/- 9 years; 116 caregivers, 54 noncaregiving controls). Demographic factors, diseases, drugs, and lifestyle variables potentially affecting inflammation and coagulation were obtained by history and adjusted for as covariates in statistical analyses. RESULTS: Caregivers had higher mean levels of IL-6 (1.38 +/- 1.42 vs 1.00 +/- 0.92 pg/mL, p =.032) and of D-dimer (723 +/- 530 vs 471 +/- 211 ng/mL, p <.001) than controls had. CRP levels were similar between groups (p =.44). The relationship between caregiver status and D-dimer was independent of covariates (p =.037) but affected by role overload. Age accounted for much of the relationship with IL-6. After controlling for covariates, the interaction between caregiver status and age was significant for D-dimer (beta =.20, p =.029) and of borderline significance for IL-6 (beta =.17, p =.090). Post hoc regression analyses indicated that, among caregivers, age was significantly correlated with both D-dimer (beta =.50, p <.001) and IL-6 (beta =.38, p =.001). Among controls, however, no significant relationship was observed between age and either D-dimer or IL-6. CONCLUSIONS: The interaction between caregiving status and age for D-dimer and IL-6 suggests the possibility that older caregivers could be at risk of a more rapid transition to the frailty syndrome and clinical manifestations of cardiovascular diseases.

Multidimensional preventive home visit programs for community-dwelling older adults: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND: Multidimensional preventive home visit programs aim at maintaining health and autonomy of older adults and preventing disability and subsequent nursing home admission, but results of randomized controlled trials (RCTs) have been inconsistent. Our objective was to systematically review RCTs examining the effect of home visit programs on mortality, nursing home admissions, and functional status decline. METHODS: Data sources were MEDLINE, EMBASE, Cochrane CENTRAL database, and references. Studies were reviewed to identify RCTs that compared outcome data of older participants in preventive home visit programs with control group outcome data. Publications reporting 21 trials were included. Data on study population, intervention characteristics, outcomes, and trial quality were double-extracted. We conducted random effects meta-analyses. RESULTS: Pooled effects estimates revealed statistically nonsignificant favorable, and heterogeneous effects on mortality (odds ratio [OR] 0.92, 95% confidence interval [CI], 0.80-1.05), functional status decline (OR 0.89, 95% CI, 0.77-1.03), and nursing home admission (OR 0.86, 95% CI, 0.68-1.10). A beneficial effect on mortality was seen in younger study populations (OR 0.74, 95% CI, 0.58-0.94) but not in older populations (OR 1.14, 95% CI, 0.90-1.43). Functional decline was reduced in programs including a clinical examination in the initial assessment (OR 0.64, 95% CI, 0.48-0.87) but not in other trials (OR 1.00, 95% CI, 0.88-1.14). There was no single factor explaining the heterogenous effects of trials on nursing home admissions. CONCLUSION: Multidimensional preventive home visits have the potential to reduce disability burden among older adults when based on multidimensional assessment with clinical examination. Effects on nursing home admissions are heterogeneous and likely depend on multiple factors including population factors, program characteristics, and health care setting.

Preclinical disability as a risk factor for falls in community-dwelling older adults

BACKGROUND: Falls are common and serious problems in older adults. The goal of this study was to examine whether preclinical disability predicts incident falls in a European population of community-dwelling older adults. METHODS: Secondary data analysis was performed on a population-based longitudinal study of 1644 community-dwelling older adults living in London, U.K.; Hamburg, Germany; Solothurn, Switzerland. Data were collected at baseline and 1-year follow-up using a self-administered multidimensional health risk appraisal questionnaire, including validated questions on falls, mobility disability status (high function, preclinical disability, task difficulty), and demographic and health-related characteristics. Associations were evaluated using bivariate and multivariate logistic regression analyses. RESULTS: Overall incidence of falls was 24%, and increased by worsening mobility disability status: high function (17%), preclinical disability (32%), task difficulty (40%), test-of-trend p <.003. In multivariate analysis adjusting for other fall risk factors, preclinical disability (odds ratio [OR] = 1.7, 95% confidence interval [CI], 1.1-2.5), task difficulty (OR = 1.7, 95% CI, 1.1-2.6) and history of falls (OR = 4.7, 95% CI, 3.5-6.3) were the strongest significant predictors of falls. In stratified multivariate analyses, preclinical disability equally predicted falls in participants with (OR = 1.7, 95% CI, 1.0-3.0) and without history of falls (OR = 1.8, 95% CI, 1.1-3.0). CONCLUSIONS: This study provides longitudinal evidence that self-reported preclinical disability predicts incident falls at 1-year follow-up independent of other self-reported fall risk factors. Multidimensional geriatric assessment that includes preclinical disability may provide a unique early warning system as well as potential targets for intervention.