Biogenic hydroxyapatite (Apatite II™) dissolution kinetics and metal removal from acid mine drainage

Apatite II™ is a biogenic hydroxyapatite (expressed as Ca(5)(PO(4))OH) derived from fish bone. Using grains of Apatite II™ with a fraction size between 250 and 500 μm, batch and flow-through experiments were carried out to (1) determine the solubility constant for the dissolution reaction Ca(5)(PO(4))(3)(OH) ⇔ 5Ca(2+) + 3PO(4)(3-) + OH(-), (2) obtain steady-state dissolution rates over the pH range between 2.22 and 7.14, and (3) study the Apatite II™'s mechanisms to remove Pb(2+), Zn(2+), Mn(2+), and Cu(2+) from metal polluted water as it dissolves. The logK(S) value obtained was -50.8±0.82 at 25 °C. Far-from-equilibrium fish-bone hydroxyapatite dissolution rates decrease by increasing pH. Assuming that the dissolution reaction is controlled by fast adsorption of a proton on a specific surface site that dominates through the pH range studied, probably ≡PO(-), followed by a slow hydrolysis step, the dissolution rate dependence is expressed in mol m(-2) s(-1) as where Rate(25 °C) = -8.9 × 10(-10) × [9.96 × 10(5) × a(H+)]/[1 + 9.96 × 10(5) × a(H+)] where a(H+) is the proton activity in solution. Removal of Pb(2+), Zn(2+), Mn(2+) and Cu(2+) was by formation of phosphate-metal compounds on the Apatite II™ substrate, whereas removal of Cd(2+) was by surface adsorption. Increase in pH enhanced the removal of aqueous heavy metals. Using the kinetic parameters obtained (e.g., dissolution rate and pH-rate dependence law), reactive transport simulations reproduced the experimental variation of pH and concentrations of Ca, P and toxic divalent metal in a column experiment filled with Apatite II™ that was designed to simulate the Apatite II™-metal polluted water interaction.

The Effect of Hydrogen Peroxide Concentration on the Oxidative Dissolution of Unirradiated Uranium Dioxide

The dissolution rate of unirradiated uranium dioxide was studied in batch experiments as a function of hydrogen peroxide concentration (from 10−5 to 10−3 mol dm−3). Unirradiated UO2(s) was used in order to differentiate surface chemical processes from radiolytic effects. Dissolution rates were determined from both uranium release and hydrogen peroxide consumption. Results showed that H2O2consumption rate was higher than UO2 dissolution rate. This observation may indicate that the overall UO2 oxidative dissolution process would be controlled by the dissolution of the oxidized solid surface. The calculated hydrogen peroxide reaction order was 1 in the H2O2 concentration range from 10−5 to 10−4 mol dm−3, while at higher concentrations no clear dependence was observed.

The Solubility of Unirradiated UO2 In Both Perchlorate And Chloride Test Solutions. Influence of the Ionic Medium

The solubility of a crystalline unirradiated UO2 (s) has been studied under reducing conditions at 25°C in three different ionic media: 0.008 mol dm–3 NaCIO4, 1 and 5 mol dm-3 NaCl+. The species responsible for the solubility in perchlorate medium are U(OH)3 and U(OH)4, with the stability constants log β13 = -0.4(±0.2) and log β14 = -5.7(±0.1), respectively. The solubility in both1! and 5 M chloride media is explained at pH values higher than 6 by the species U(OH)4 with log β14 = -5.5(±0.2) while at lower pH values an abnormal behaviour is observed, with higher uranium concentrations in solution and a proton independent solubility for pH values lower than 4. The XPS observations of the reacted solids do not show the presence of solid surface phases other than uranium dioxide, with an upper oxidation state of UO2.1.

A validation study of the hospital anxiety and depression scale (HADS) in a Spanish population

The present study aims to validate the Spanish version of the Hospital Anxiety and Depression Scale (HADS) and to determine the use of this tool for screening mood and anxiety disorders. Psychometric properties of the HADS were assessed in different groups of general medical outpatients attending the Hospital Clínic in Barcelona (N=385), and psychiatric diagnoses were made using DSM-IV criteria. A two-factor solution corresponding to the original two subscales of the HADS was found. The Spanish version of the HADS had good internal consistency and external validity, with favorable sensitivity and specificity in identifying cases of psychiatric disorder as defined by the Structured Clinical Interview for DSM-IV (SCID-I). The psychometric properties of the HADS and its brevity make it useful for screening for psychiatric disorders in the medically ill.

Effectiveness of CPAP treatment in daytime function in sleep apnea syndrome: a randomized controlled study with an optimized placebo

Application of continuous positive airway pressure (CPAP) as the standard treatment for sleep apnea/hypopnea syndrome (SAHS) is a moot point. Studies on the effectiveness of this treatment have been challenged because of the lack of a suitable placebo. The recent description of a true placebo (sham CPAP) prompted us to conduct a randomized trial of CPAP or placebo to assess the effectiveness of CPAP in improving SAHS-related symptoms and daytime function in patients with moderate to severe SAHS. Forty-eight patients, stratified in four groups according to severity, were randomly allocated into two treatment groups (optimal and sham CPAP) for a 6-wk period. Of these, 45 completed follow-up (91% males; age: 54 +/- 10 yr; body mass index [BMI]: 32 +/- 6 kg/m(2); apnea-hypopnea index [AHI]: 54 +/- 19 events/h; and Epworth Sleepiness Scale [ESS]: 16 +/- 5). The ESS, a questionnaire on SAHS-related symptoms, Functional Outcomes Sleep Questionnaire (FOSQ), and the Short Form Health Survey (SF-36) were completed at inclusion and after treatment. After 10 d of washout, the placebo group was treated with optimal CPAP and reassessed before and after optimal CPAP. The group receiving optimal CPAP when compared with the group with sham CPAP showed considerably greater improvement in the relief of sleepiness (-9.5 versus -2.3, p < 0.001), other SAHS-related symptoms (-18.5 versus -4.5, p < 0.001), vigilance (+8.5 versus +3.4, p = 0.009), and general productivity (+4.0 versus +0.5, p = 0.04) FOSQ scales. Both groups used a similar number of hours for the optimal and the sham CPAP (4.3 versus 4.5, (p = NS). The patients initially treated with placebo CPAP improved significantly more when optimal CPAP was applied for ESS (-2.3 versus -6.7, p < 0.001) and other sleep apnea syndrome (SAS)-related symptoms (-4.5 versus -11.2, p = 0.02). Our study provides strong evidence of the effectiveness of CPAP treatment in improving symptoms and perceived health status in moderate to severe SAHS.

Preliminary data of a prospective study on neuropsychiatric side effects after initiation of efavirenz

OBJECTIVE

To assess baseline variables able to predict neuropsychiatric side effects (NPSEs) associated with the initiation of an efavirenz (EFV)-containing regimen in HIV-1-infected patients.

DESIGN

Open-label, prospective, observational study.

METHODS

Consecutive HIV-1-infected outpatients in whom EFV was prescribed underwent a psychiatric interview. At baseline and at 2, 4, and 12 weeks, patients completed the Symptoms Check List-90-Revised (SCL-90-R), the Medical Outcome Study for HIV-positive patients (MOS-HIV), and a standardized questionnaire concerning potential NPSEs.

RESULTS

Preliminary data showed that discontinuation of EFV because of NPSEs occurred in 4 of 31 patients (13%). Patients who completed the follow-up showed a decrease in SCL-90-R total score (p =.004) and in several subscales such as Interpersonal Sensitivity (p =.009), Depression (p =.001), and Anxiety (p =.040), whereas no changes in MOS-HIV were observed. Having fewer years of education (p =.006), having fewer baseline central nervous symptoms (p =.000), reporting better baseline physical status (p =.013), and having higher baseline scores in the Heath Transition subscale of the MOS-HIV (p =.000) and in the Somatization subscale of the SCL-90-R (p =.002) were associated with more NPSEs.

CONCLUSION

Patients maintained on EFV showed a decrease in psychologic distress related to self-image, depression, and anxiety, without any effect on quality of life. Patients with a lower level of education, those who feel physically and psychologically better at baseline than in the past, and those who suffer from more distress as a result of physical complaints may be at greater risk of reporting more NPSEs after EFV initiation.

Theory for phase transitions in diblock copolymers: the lamellar case

A mean-field type theory is proposed to study order-disorder transitions (ODT's) in block copolymers. The theory applies to both the weak segregation and the strong segregation regimes. An energy functional is proposed without appealing to the random phase approximation (RPA). We find additional terms unaccounted for within the RPA. We work out in detail transitions to the lamellar state and compare the method to other existing theories of the ODT and numerical simulations. We find good agreement with recent experimental results and predict that the intermediate segregation regime may have more than one scaling behavior.

[Hyperviscosity syndrome and mental disorders]

The hyperviscosity syndrome has been described clinically as the triad of bleeding, visual signs and neurological manifestations associated with elevated serum viscosity. Several reports have recognised an association between hyperviscosity and altered mental status. Since to our knowledge only a case of hyperviscosity-induced delirium has been described (1), we raise the possibility of this diagnosis in the most of this reported cases, based on the nature of the symptoms, sudden onset and fluctuating course, and its resolution with plasmapheresis. In this paper we review the literature about hyperviscosity syndrome and altered mental status. In conclusion, serum hyperviscosity should be added to the large list of causes altered mental status, especially of delirium. Since plasmapheresis can reverse clinical symptoms, it early recognition and the measurement of serum viscosity is essential in patients suffering from diseases that may lead to this syndrome, and who develop psychiatric symptoms.

Rapidly cycling bipolar II disorder following liver transplantation

During the last decade the psychiatric aspects of liver transplantation have been widely described. Although affective complications are some of the most prevalent, a complete and persistent bipolar II syndrome following transplantation has never been reported before. In this paper we describe a patient who developed a rapidly cycling bipolar II disorder after liver transplantation. He presented a major depressive episode within the first 48 hours following transplantation, and subsequently started cycling from depression to hypomania with only brief periods of euthymia. One year after transplantation, only lithium carbonate has proved to be useful to ameliorate his persistent disorder. There was no premorbid or family history of affective illness. Although the course of the disorder seemed to be independent from any pharmacologic or psychosocial factor, it is suggested that transplantation, corticosteroids, and cyclosporine may have played some role in the pathogenesis of the syndrome.

Identification of organophosphorus insecticides and their hydrolysis products by liquid chromatography in combination with UV and thermospray-mass spectrometric detection

Liquid chromatography with ultraviolet detection (LC-UV) and positive and negative ion mode (PI and NI, respectively) thermospray LC-mass spectrometry (LC-MS) were used for the analysis of the organophosphorus pesticides azinphos-methyl, diazinon and parathion-methyl and their corresponding breakdown products obtained after basic hydrolysis (pH 7-11). LC analysis was performed in the reversed-phase mode using methanol-water (80:20) or methanol-water (70:30) + 0.1 M ammonium acetate for LC-UV or LC-MS, respectively. By employing NI thermospray LC-MS the identification of p-nitrophenol, showing the [2M-H]- ion as the base peak, was feasible and confirmed the LC-UV chromatogram at 220 nm. When the PI mode was used, [M + NH4]+ and [M + H]+ ions were obtained as base peaks for azinphos-methyl and diazinon, respectively. The degradation rates varied from diazinon, which showed no degradation during a period of ten days, to azinphos-methyl and parathion-methyl, for which degradation occurred rapidly when the pH was increased from 7 to 11.