Evaluating dual-domain models for upscaling multicomponent reactive transport in mine waste rock.

Reactive transport models have proven abilities to simulate the quantity and quality of drainage from mine waste rock. Tracer experiments indicate the presence of fast and slow flow regimes in many heterogeneous waste-rock piles. Although multidomain models have been developed specifically for systems with such distinctive hydrodynamics, there have been limited applications of multidomain reactive transport models to simulate composite drainage chemistries from waste-rock piles to date. This work evaluated the ability of dual-domain multicomponent reactive transport models (DDMRTMs) to reproduce breakthrough curves of conservative (chloride) and reactive (molybdenum) solutes observed at a well-characterized experimental waste-rock pile at the Antamina Mine, Peru. We found that the DDMRTM simulations quantitatively matched eight-year-long records of conservative transport through the waste-rock pile when parameterized mainly with field-measured properties obtained from the site and limited calibration. The DDMRTM model also provided a reasonable match to field observations of the reactive solute. The limited calibrated parameters are physically realistic, corroborating the ability of these multidomain models to reproduce the complex reactive-transport processes governing polluted rock drainage from large-scale waste-rock piles.

Evaluation of single- and dual-porosity models for reproducing the release of external and internal tracers from heterogeneous waste-rock piles.

Accurate predictions of solute release from waste-rock piles (WRPs) are paramount for decision making in mining-related environmental processes. Tracers provide information that can be used to estimate effective transport parameters and understand mechanisms controlling the hydraulic and geochemical behavior of WRPs. It is shown that internal tracers (i.e. initially present) together with external (i.e. applied) tracers provide complementary and quantitative information to identify transport mechanisms. The analysis focuses on two experimental WRPs, Piles 4 and Pile 5 at the Antamina Mine site (Peru), where both an internal chloride tracer and externally applied bromide tracer were monitored in discharge over three years. The results suggest that external tracers provide insight into transport associated with relatively fast flow regions that are activated during higher-rate recharge events. In contrast, internal tracers provide insight into mechanisms controlling solutes release from lower-permeability zones within the piles. Rate-limited diffusive processes, which can be mimicked by nonlocal mass-transfer models, affect both internal and external tracers. The sensitivity of the mass-transfer parameters to heterogeneity is higher for external tracers than for internal tracers, as indicated by the different mean residence times characterizing the flow paths associated with each tracer. The joint use of internal and external tracers provides a more comprehensive understanding of the transport mechanisms in WRPs. In particular, the tracer tests support the notion that a multi-porosity conceptualization of WRPs is more adequate for capturing key mechanisms than a dual-porosity conceptualization.

Implications of the change in confinement status of a heterogeneous aquifer for scale-dependent dispersion and mass-transfer processes.

A series of experimental tracer tests were performed to explore the implications of the change in the pressure status of a heterogeneous bimodal aquifer for scale-dependent dispersion and mass-transfer processes. The sandbox was filled with sands and gravel channels and patches to form an alluvial-like bimodal aquifer. We performed multiple injections of a conservative tracer from 26 different locations of the sandbox and interpreted the resulting depth-integrated breakthrough curves (BTCs) at the central pumping well to obtain a scale-dependent distribution of local and field-integrated apparent longitudinal dispersivity (respectively, αLloc and αLapp). We repeated the experiments under confined (CS) and unconfined (UNS) pressure status, keeping the same heterogeneous configuration. Results showed that αLloc(associated with transport through gravel zones) was poorly influenced by the change in aquifer pressure and the presence of channels. Instead, αLapp(i.e. macrodispersion) strongly increased when changing from CS to UNS. In specific, we found αLapp≈0.03r for the CS and αLapp≈0.15r for the UNS (being r the distance from the well). Second-to-fourth-order temporal moments showed strong spatial dependence in the UNS and no spatial dependence in the CS. These results seem consistent with a "vadose-zone-driven" kinetic mass-transfer process occurring in the UNS but not in the CS. The vadose zone enhances vertical flow due to the presence of free surface and large contrasts in hydraulic conductivity triggered by the desaturation of gravel channels nearby the pumping well. The vadose zone enhances vertical mixing between gravel and sands and generates BTC tailing. In the CS vertical mixing is negligible and anomalous transport is not observed.

[A case of pulmonary aspergillosis effectively treated with itraconazole. Possible interaction of the antimycotic agent with hydroquinidine]. / Un caso di aspergillosi polmonare trattato efficacemente con itraconazolo. Possibile interferenza dell'antimicotico con la idrochinidina.

This study describes a case of pulmonary aspergilloma in a neutropenic patient affected with myelodysplastic syndrome. It reports the therapeutic efficacy of itraconazole, emphasizing in particular the possible interaction with quinidine, with QT prolongation--at ECG--disappeared after quinidine withdrawal.

[A case of intestinal schistosomiasis with hepatic involvement: interdisciplinary diagnostic approach and peculiarity of the echographic and histologic findings]. / Un caso di schistosomiasi intestinale con interessamento epatico: approccio diagnostico interdisciplinare e peculiarità dei reperti ecografico e istologico.

We report a case of intestinal schistosomiasis; secondary hepatic involvement is particularly described, with a very distinctive ecographic feature of portal hypertension and a bioptic picture stressing a granulomatous periportal inflammation. In the work we emphasize the importance of a multidisciplinary approach (physicians working in the fields of internal medicine, infectious disease, gastrointestinal diseases, radiologist, pathologist) in the course of diagnostic investigation. Finally, we confirm the effectiveness of praziquantel against Schistosoma mansoni.

[EDTA-induced pseudothrombocytopenia]. / Pseudotrombocitopenia da EDTA.

EDTA-induced pseudothrombocytopenia is a laboratory artifact caused in vitro by platelet aggregation, due to IgG or IgM class antibodies reacting with antigenic binding site of the GP IIb glycoprotein. Pseudothrombocytopenia is rarely found (about 1% of platelets counts), but must be considered in the differential diagnosis of thrombocytopenia, since it could lead to useless investigations and therapies. We report three patients with pseudothrombocytopenia, one of whom underwent bone marrow biopsy and danazol treatment, before establishing the correct diagnosis. The absence of hemorrhagic manifestations with persisting low platelets counts led to a re-examination of peripheral blood smear and to the diagnosis of pseudothrombocytopenia. Therefore a morphological platelets evaluation and their count on citrate-anticoagulated blood must be performed in every patient under assessment for thrombocytopenia.

[Difference in the behavior of T-lymphocyte populations in heroin and methadone addicts]. / Differenza nel comportamento delle popolazioni T-linfocitarie nei dipendenti da eroina e da metadone.

An assessment of T-lymphocyte populations was performed in two groups of drug addicts by the technique of monoclonal antibodies. Group I was composed of 11 asymptomatic heroin addicts, group II being in heroin withdrawal program from at least six months. Homosexual subjects, partners of patients with AIDS and patients with liver abnormalities or with recent infectious diseases were excluded from the present study. In all the examined subjects the antibody pattern to Toxoplasma gondii, Epstein-Barr virus, Cytomegalovirus was either negative or slightly positive as after old infections. All subjects were HBsAg negative and HBsAb positive. Group I patients showed a significant inversion of OKT4/OKT8 ratio (p less than 0.01), due to a reduction in T helper lymphocytes (p less than 0.05) and an increase in T suppressors (p less than 0.05). Both groups showed a not significantly different proliferative response to Phytohemagglutinin (PHA) and Concanavalin A (Con A), although 8 out of 11 patients of group I exhibited a reduced proliferative response to PHA. Group I patients also showed a reduced proliferative response to Pokeweed mitogen (PWM). These results might suggest an involvement of B-lymphocytes in immunological changes of heroin addicts. In group II patient all the examined variables, OKT4/OKT8 ratio, absolute number as well as percentage of T-lymphocytes subpopulations and proliferative responses to the employed mitogens, resulted in the normal range. These data seem to exclude that methadone, in contrast with heroin, may induce a cell-mediated immunodepression.(ABSTRACT TRUNCATED AT 250 WORDS)

[Changes in several immunological parameters and the presence of anti-HTLV III antibodies in drug addicts]. / Modificazioni di alcuni parametri immunologici e presenza di anticorpi anti-HTLV III in tossicodipendenti.

The immunological picture in a group of heroin addicts and in a methadone treated group was evaluated. Ninety-six per cent shows modifications of the lymphocyte pattern, independently of the type of opium derivative administered. The OKT4/OKT8 ratio considered one of the hallmarks of acquired immunodeficiency, turns out to be reduced in 64.6% of the cases. In these latter the most outstanding defect is made up by the T-helper drop (83.8% of cases), limited to 23.5% in the group with normal OKT4/OKT8 ratio. The most significant variant between the two groups is represented by the positivity of anti-HTLV III test, which switches from 47 to 74.1% in the patients with reduced ratio. Immunoglobulins turn out to be increased in 81.2% of the cases, independently of the opium derivative administered and without significant differences in relation to the OKT4/OKT8 ratio. Therefore two immunological patterns seem to coexist in the population studied, which very likely represents two evolutive moments of the same disorder with an earlier phase of hyperimmune condition from a persistent antigenic stimulation which characterizes the situation at risk. In a later phase, the impact of HTLV III infection causes the deletion of the lymphocyte helper subpopulation which elicits the immunodepressive situation.

HIV-related thrombotic thrombocytopenic purpura (TTP) as first clinical manifestation of infection.

A case of thrombotic thrombocytopenic purpura (TTP) in a 40-year-old bisexual man unaware of being HIV positive is reported. The hematologic syndrome represented the first clinical manifestation of this viral infection. The clinical picture, characterized by severe hemolytic microangiopathic anemia, thrombocytopenia, fluctuating neurologic abnormalities and fever, quickly improved after plasma exchange and corticosteroid therapy. Two blood tests showed severe depletion of the CD4+ lymphocyte count and HIV antigenemia was positive. This case represents a clinical epiphenomenon of HIV infection in an advanced phase. According to recent CDC criteria the patient should be considered in AIDS. Antiretroviral treatment was started and after nine months of follow-up there has been no relapse.

Effects of recombinant human stem cell factor (rh-SCF) on colony formation and long-term bone marrow cultures (LTBMC) in patients with myelodysplastic syndromes.

Stem cell factor (SCF), the ligand of the c-kit receptor, is a potent enhancing cytokine for haematopoietic cells in the presence of IL-3, GM-CSF and erythropoietin (Epo). In the clonogenic assays of 63 MDS patients, the addition of rh-SCF + GM-CSF and/or IL-3 induced a significant increase (p < 0.001) in the number and size of CFU-GM. Never reaching the levels of controls, this increase was seen in all FAB subtypes, but particularly in RA. There was no significant increase in cluster formation, even in RAEB or RAEBt. Rh-SCF (10 ng/ml) led to mean increases of up to 26 times in the number of Epo-dependent BFU-E colonies, particularly in RA (p < 0.001) and RAEB (p < 0.05). Individual responses varied widely (especially in RA) from no response to supranormal levels. Added to the weekly refeed of 37 MDS LTBMC, SCF (10 ng/ml) induced only a 7% mean increase in both cell output and the number of clonogenic cells recovered in the supernatant. Immunohistochemical examination of the supernatant showed significant increases in differentiating myeloid cells in all examined cases, and in erythroid cells in 3 cases; blast cells increased in only 3 cases. These data suggest that rh-SCF is capable of at least partially reversing defective MDS myeloid haematopoiesis, and leads no overt risk of leukaemic transformation. Its potent effect on erythroid cells is encouraging for future clinical applications in patients, particularly if they are selected by means of in vitro tests.