62,914 research outputs found
The behavior at non-ambient conditions of colemanite: a hydrous Ca-borate
No full textColemanite, CaB3O4(OH)3·H2O, is a common hydrous borate of large economic relevance, as it is one of the major commodities of boron with applications in the fields of glass and ceramic industries. Colemanite-rich layers are usually found in stratigraphic successions related to lacustrine basins in semi-arid to arid environments, associated to a local volcanic activity, which provides the source for boron. Despite the large economic relevance, the behavior of this mineral at non-ambient conditions of temperature and pressure was almost unexplored, which can provide a basis for understanding its stability during diagenetic and metamorphic processes. In this contribution, we report the highpressure behavior of colemanite (Lotti et al., 2017), based on in situ single-crystal synchrotron X-ray diffraction data up to 24 GPa, and its low-T behavior by in situ X-ray and neutron single-crystal diffraction. Colemanite was found to be stable up ~ 14.5 GPa, where a reconstructive phase transition towards a high-pressure polymorph (colemanite-II) with same symmetry (space group P21/a), but a six times larger unit cell volume, occurs. The elastic behavior of colemanite was described by fitting the experimental data with a III-order Birchurnaghan equation of state, yielding the following refined elastic parameters: KV0 = 64(4) GPa and KV' 5.5(7). The colemanite-tocolemanite-II phase transition induces an increase in the average coordination number of both the Ca and B cations. In particular, a fraction of the boron sites increases its coordination from triangular to tetrahedral by making a further bond with a H2O-oxygen atom. Although the phase transition occurs (at ambient temperature) at pressures far from those associated with the usual geologic environments of colemanite, the reported results disclosed flexible deformation mechanisms that borate compounds may adopt to accommodate pressure, thus providing new insights on the behavior of borate minerals at non-ambient conditions. The complex hydrogen-bonding network of olemanite has also been characterized, at ambient and low temperature conditions, by means of in situ single-crystal synchrotron X-ray and neutron diffraction experiments. A positional disorder, related to the presence of two mutually exclusive configurations of the H2O-molecule hydrogen atoms, was found both above and below ~ 0°C, where a displacive phase transition from the P21/a to the P21 space group occurs.
Lotti, P., Gatta, G.D., Comboni, D., Guastella, G, Merlini, M., Guastoni, A., Liermann, H.-P. (2017): High-pressure behavior and Pinduced phase transition of CaB3O4(OH)3*H2O (colemanite), J. Am. Ceram. Soc., in press, DOI: 10.1111/jace.14730
High-temperature behavior and dehydration of the natural borate colemanite
No full textColemanite, CaB3O4(OH)3*H2O, is the most common natural hydrous calcium borate and one of the most important mineral commodities for boron. It is mainly extracted from Turkish deposits, which form for the chemical precipitation of colemanite from relatively diluted waters of lacustrine basins, hosted in continental semi-arid to arid environments and fed by B-rich hydrothermal springs related to a local volcanic activity (e.g. Helvaci & Alonso, 2000). Due to its common occurrence in waste rocks at extraction sites, several studies have been focused in the recent past on the exploitation of colemanite as raw material, for example as an additive in the production of lightweight cements (Targan et al., 2003) or radiation shielding materials (Glinicki et al., 2018). However, despite the relevance beared in the applications of colemanite, we still have only a partial knowledge of the high-temperature behavior of this mineral compound.
In this study we investigated the high-temperature behavior of a natural sample of colemanite from the Bigadiç deposit (Turkey), by means of in situ powder synchrotron X-ray diffraction, performed at the MCX beamline of Elettra (Trieste, Italy), using a hot blower device.
The refined unit-cell parameters and structures show a significantly anisotropic thermal expansion, which is only accommodated along the b and c crystallographic axes, whereas the a axis, corresponding to the direction of the chains of B-coordination polyhedra, is almost unaffected. Between 275 and 325 °C, a reduction in the unit-cell volume and a decrease in the refined occupancy of the H2O-oxygen site, reveal the occurrence of a dehydration mechanism, which is followed by a complete and irreversible amorphization between 325 and 375 °C.
Merging the V-T data of this experiment with those obtained in a previous low-T experiment on the same natural sample (Lotti et al., 2018), a thermal Berman equation of state was refined in the range from -171 to 250 °C (104-525 K), yielding a thermal expansion coefficient at ambient-T (αV298K) of 4.5(1)*10-5 K-1 and α1 = 5.7(8)*10-8 K-2.
Glinicki M.A., Antolik A. & Gawlicki M. 2018. Evaluation of compatibility of neutron-shielding boron aggregates with Portland cement in mortar. Constr. Build. Mater., 164, 731-738.
Helvaci C. & Alonso R.N. 2000. Borates Deposits of Turkey and Argentina: A Summary and Geological Comparison. Turkish J. Earth Sci., 9, 1-27.
Lotti P., Gatta G.D., Demitri N., Guastella G., Rizzato S., Ortenzi M.A., Magrini F., Comboni D., Guastoni A. & Fernandez-Diaz M.T. 2018. Crystal chemistry and temperature behavior of the natural hydrous borate colemanite, a mineral commodity of boron. Phys. Chem. Minerals, in press DOI: https://doi.org/10.1007/s00269-017-0929-7.
Targan S., Olgun A., Erdogan Y., & Sevinc V. 2003. Influence of natural pozzolan, colemanite ore waste, bottom ash, and fly ash on the properties of Portland cement. Cement Concrete Res., 33, 1175-1182
The effect of psychosocial interventions on depression, anxiety, and quality of life in hemodialysis patients: a systematic review and a meta-analysis
No full textPurpose: Hemodialysis has become a standard therapy for adults with end-stage renal diseases. Adults undergoing hemodialysis have to cope with unique psychological issues that make their care journey particularly fatiguing. In this systematic review and meta-analysis, we aimed to summarize and evaluate the effects of psychosocial interventions on the reduction of anxiety and depression in adults with HDs. Methods: We included randomized controlled trials and quasi-experimental studies that measure change in depression, anxiety, and quality of life. Results: We identify three categories of psychosocial interventions delivered to adults undergoing hemodialysis. Based on our analysis, there was a medium effect of psychosocial intervention on depression (SMD − 0.85, 95%CI − 1.17; − 0.52, I2 = 80%, p < 0.01) and anxiety (SMD − 0.99, 95%CI − 1.65; − 0.33, I2 = 88%, p < 0.01) in adults undergoing hemodialysis. Conclusions: Psychosocial interventions, such as psychological support or relaxation-based therapy, seems all to reduce depression and anxiety in adults undergoing HD. Preliminary evidence suggests that there may be a benefit of psychosocial interventions on the quality of life for adults undergoing HD
Effects of different peritoneal dialysis fluids on the TH1/TH2 balance
No full textBackground. Peritoneal dialysis (PD) is associated with a depression of T cell function, as suggested by the impaired production of cytokines by Th cells collected from PD patients. Although treatment biocompatibility could be implicated in this immune dysfunction, it has been poorly investigated, thus far. Therefore, we undertook a study aiming to analyze the effects of different peritoneal dialysis fluids on the Th1/Th2 balance in PD patients. Methods. Twenty three patients on continuous ambulatory peritoneal dialysis (CAPD) were evaluated. Seven patients were on CAPD with icodextrin solution (ICO-PD), seven with glucose and lactate/bicarbonate-buffered solution (LAC/BIC-PD), and nine with glucose and lactate-buffered solution (LAC-PD). The Th1/Th2 balance was evaluated by measuring IFN-gamma (Th1 subset) and IL-4 (Th2 subset), both in circulating and peritoneum-derived Th lymphocytes unstimulated or stimulated by phytohemoagglutinin (PHA). Moreover inflammatory, nutritional and dialysis-related parameters were recorded. Eight normal subjects comprised the control group (CON). Results. Circulating T cells: IFN-gamma was significantly lower in the LAC-PD group (p<0.05) compared to the ICO-PD and LAC/BIC-PD groups. The IFN-gamma/IL-4-producing cell ratio was significantly lower in PD patients than in CON. Peritoneal T cells: after 24-h PHA stimulation, IFN-gamma increased in all patients, but the rise was less pronounced in the LAC-PD group (p<0.05) than in the other two PD groups. The Th1/Th2 ratio was significantly lower in the LAC-PD group when compared both to LAC/BIC-PD and ICO-PD groups. In addition, the LAC-PD group presented a significantly higher rate of peritoneal infections compared to the other PD groups. Conclusions. CAPD with lactate-buffered peritoneal fluid has deleterious effects on the Th1 cell subset, while the use of more biocompatible fluids, bicarbonate-buffered and icodextrin, is associated with a more physiologically representative Th1/Th2 balance and a reduced peritonitis rate
Erratum to: Effect of moderate red wine intake on cardiac prognosis after recent acute myocardial infarction of subjects with Type 2 diabetes mellitus (Diabetic Medicine, (2006), 23, 9, (974-981), 10.1111/j.1464-5491.2006.01886.x)
No full textIn an article by Marfella et al, the author name C. Saron is incorrect and should be listed as C. Sardu. Therefore the correct author list is: R. Marfella, F. Cacciapuoti, M. Siniscalchi, F. C. Sasso, F. Marchese, F. Cinone, E. Musacchio, M. A. Marfella, L. Ruggiero, G. Chiorazzo, D. Liberti, G. Chiorazzo, G. F. Nicoletti, C. Sardu, F. D'Andrea, C. Ammendola, M. Verza and L. Coppola.In an article by Marfella et al, the author name C. Saron is incorrect and should be listed as C. Sardu. Therefore the correct author list is: R. Marfella, F. Cacciapuoti, M. Siniscalchi, F. C. Sasso, F. Marchese, F. Cinone, E. Musacchio, M. A. Marfella, L. Ruggiero, G. Chiorazzo, D. Liberti, G. Chiorazzo, G. F. Nicoletti, C. Sardu, F. D'Andrea, C. Ammendola, M. Verza and L. Coppola
Aneurysms and pseudoaneurysms in dialysis access
No full textAneurysms are a common and often difficult complication seen with arteriovenous vascular access for haemodialysis. The purpose of this narrative review is to define and describe the scale of the problem and suggested therapeutic strategies. A narrative review of the published literature illustrated by individual cases is presented with the aim of summarising the relevant literature. The definitions of aneurysm are inconsistent throughout the literature and therefore systematic review is impossible. They vary from qualitative descriptions to quantitative definitions using absolute size, relative size and also size plus characteristics. The incidence and aetiology are also ill defined but separation into true aneurysms and false, or pseudoaneurysms may be helpful in planning treatment, which may be conservative, surgical or radiological. The lack of useful definitions and classification along with the multitude of management strategies proposed make firm evidence based conclusions difficult to draw. Further robust well designed studies are required to define best practice for this common problem
Marchettiite, (NH4)C5H3N4O3, a new organic mineral from Mount Cervandone, Devero Valley, Western-Central Alps, Italy
No full textThe new mineral marchettiite (IMA2017-066) is the natural equivalent of ammonium hydrogen urate. It has a simple molecular formula
C5H7 N5 O3 and can be alternatively written as (NH4 )C 5H3 N4 O3 . Marchettiite was found in a cleft at Mount Cervandone, Devero Valley,
Piedmont, Italy, where it occurs as aggregates of opaque pale pink to white, platy prismatic crystals. This mineral has a white streak, dull
and opaque lustre, it is not fluorescent and has a hardness of 2–2.5 (Mohs’ scale). The tenacity is brittle and crystals have a good cleavage
parallel to {001}. The calculated density is 1.69 g/cm 3
. Marchettiite is biaxial (–) with 2V of 47.24°; the optical properties of marchettiite
were determined by periodic-DFT methods providing the following values: α = 1.372, β = 1.681 and γ = 1.768. No twinning was
observed. Electron microprobe analyses gave the following chemical formula: C 4.99 H6.97 N4.91 O3.00 . Although the small crystal size did
not allow refinement of structural data by single-crystal diffraction, we were able to refine the structure by powder micro X-ray diffrac-
tion. Marchettiite has space group P 1 and the following unit-cell parameters: a = 3.6533(2) Å, b = 10.2046(7) Å, c = 10.5837(7) Å, α =
113.809(5)°, β = 91.313(8)°, γ = 92.44(1)° and V = 360.312 Å3 . The strongest lines in the powder diffraction pattern [d in Å (I )(hkl)]
are: 9.784(50)(001); 8.663(80)(01 1); 5.659(100)(011); 3.443(100)(10 1); 3.241(70)(003) and 3.158(100)(1 1 1). Marchettiite is named
after Gianfranco Marchetti, the mineral collector who found this mineral
Continuous venovenous hemofiltration after coronary procedures for the prevention of contrast-induced acute kidney injury in patients with severe chronic renal failure
No full textContinuous venovenous hemofiltration (CVVH) is a renal replacement therapy that has been successfully used in patients with severe chronic renal failure to prevent contrastinduced acute kidney injury (CI-AKI). In this study, we present a consecutive experience using a new CVVH protocol that has also been applied to patients with acute coronary syndrome (ACS). CVVH was performed in consecutive patients with estimated glomerular filtration rate <30 ml/min/1.73 m(2) (mean +/- SD, 21.1 +/- 7.3 ml/min/1.73 m(2)) undergoing diagnostic or interventional coronary procedures starting after the angiographic procedures. Iopamidol was used as a contrast agent. In the first 6 patients, iopamidol removal by the CVVH hemofilter and kidney was calculated by measuring iopamidol concentrations in the blood, urine, and ultrafiltrate collected during the 6-hour CVVH session. In the second phase, the protocol was applied to 47 additional patients meeting the inclusion criteria. Six-hour CVVH resulted in iopamidol removal comparable with that of 12-hour diuresis (43 +/- 12% vs 42 +/- 15% of administered, p = NS). CI-AKI occurred in 7.5% of patients in the whole population and no patients had acute pulmonary edema, need for dialysis, or any major bleeding. In conclusion, in a population including patients with ACS with severe chronic renal failure undergoing coronary angiographic procedures, 6-hour CVVH performed only after contrast medium exposure was able to remove an amount of contrast medium similar to that removed by the kidneys in 12 hours and resulted in a low rate of CI-AKI
New scenarios in secondary hyperparathyroidism: etelcalcetide. Position paper of working group on CKD-MBD of the Italian Society of Nephrology
No full textBone mineral abnormalities (defined as Chronic Kidney Disease Mineral Bone Disorder; CKD-MBD) are prevalent and associated with a substantial risk burden and poor prognosis in CKD population. Several lines of evidence support the notion that a large proportion of patients receiving maintenance dialysis experience a suboptimal biochemical control of CKD-MBD. Although no study has ever demonstrated conclusively that CKD-MBD control is associated with improved survival, an expanding therapeutic armamentarium is available to correct bone mineral abnormalities. In this position paper of Lombardy Nephrologists, a summary of the state of art of CKD-MBD as well as a summary of the unmet clinical needs will be provided. Furthermore, this position paper will focus on the potential and drawbacks of a new injectable calcimimetic, etelcalcetide, a drug available in Italy since few months ago
PERITONEAL ULTRAFILTRATION IN REFRACTORY HEART FAILURE: A COHORT STUDY
No full textIntroduction: Acutely decompensated heart failure (HF) in patients with diuretic resistance is often treated with extracorporeal ultrafiltration. Peritoneal ultrafiltration (PUF) has been proposed for the long-term management of severe HF after resolution of the acute episode. The aim of the present study was to evaluate the use of PUF in the treatment of chronic refractory HF in patients without end-stage renal disease
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