Calcium sulfate minerals such as gypsum play important roles in natural and industrial processes, but their precipitation mechanisms remain largely unexplored. We used time-resolved sample quenching ...and high-resolution microscopy to demonstrate that gypsum forms via a three-stage process: (i) homogeneous precipitation of nanocrystalline hemihydrate bassanite below its predicted solubility, (ii) self-assembly of bassanite into elongated aggregates co-oriented along their c axis, and (iii) transformation into dihydrate gypsum. These findings indicate that a stable nanocrystalline precursor phase can form below its bulk solubility and that in the CaSO₄ system, the self-assembly of nanoparticles plays a crucial role. Understanding why bassanite forms prior to gypsum can lead to more efficient anti-scaling strategies for water desalination and may help to explain the persistence of CaS0 4 phases in regions of low water activity on Mars.
We have synthesized inorganic micron-sized filaments, whose microstucture consists of silica-coated nanometer-sized carbonate crystals, arranged with strong orientational order. They exhibit ...noncrystallographic, curved, helical morphologies, reminiscent of biological forms. The filaments are similar to supposed cyanobacterial microfossils from the Precambrian Warrawoona chert formation in Western Australia, reputed to be the oldest terrestrial microfossils. Simple organic hydrocarbons, whose sources may also be abiotic and indeed inorganic, readily condense onto these filaments and subsequently polymerize under gentle heating to yield kerogenous products. Our results demonstrate that abiotic and morphologically complex microstructures that are identical to currently accepted biogenic materials can be synthesized inorganically.
The influence of climate variation on the availability of water resources was analyzed in the headwaters of the Tagus River basin using two drought indices, the standardized precipitation index (SPI) ...and the standardized precipitation evapotranspiration index (SPEI). This basin is highly regulated and strategic, and contains two hyperannual reservoirs that are the origin of the water supply system for Mediterranean areas of southeast Spain. The indices confirmed that drought conditions have prevailed in the headwaters of the Tagus River since the 1970s. The responses in river discharge and reservoir storage were slightly higher when based on the SPEI rather than the SPI, which indicates that although precipitation had a major role in explaining temporal variability in the analyzed parameters, the influence of temperature was not negligible. Moreover, the greatest response in hydrological variables was evident over longer timescales of the climatic drought indices. Although the effect of climate variability on water resources was substantial during the analyzed period, we also showed a major change in hydrological–climatic relationships in regulated systems including reservoir storage and outflow. These were closely related to changes in external demand following commencement of the water transfer system to the Júcar and Segura basins after the 1980s. The marked reduction in water availability in the basin, which is related to more frequent droughts, contrasts with the amount of water transferred, which shows a clear upward trend associated with increasing water demand in the Mediterranean basin.
Archean hydrothermal environments formed a likely site for the origin and early evolution of life. These are also the settings, however, were complex abiologic structures can form. Low‐temperature ...serpentinization of ultramafic crust can generate alkaline, silica‐saturated fluids in which carbonate–silica crystalline aggregates with life‐like morphologies can self‐assemble. These “biomorphs” could have adsorbed hydrocarbons from Fischer–Tropsch type synthesis processes, leading to metamorphosed structures that resemble carbonaceous microfossils. Although this abiogenic process has been extensively cited in the literature and has generated important controversy, so far only one specific biomorph type with a filamentous shape has been discussed for the interpretation of Archean microfossils. It is therefore critical to precisely determine the full distribution in morphology and size of these biomorphs, and to study the range of plausible geochemical conditions under which these microstructures can form. Here, a set of witherite‐silica biomorph synthesis experiments in silica‐saturated solutions is presented, for a range of pH values (from 9 to 11.5) and barium ion concentrations (from 0.6 to 40 mmol/L BaCl2). Under these varying conditions, a wide range of life‐like structures is found, from fractal dendrites to complex shapes with continuous curvature. The size, spatial concentration, and morphology of the biomorphs are strongly controlled by environmental parameters, among which pH is the most important. This potentially limits the diversity of environments in which the growth of biomorphs could have occurred on Early Earth. Given the variety of the observed biomorph morphologies, our results show that the morphology of an individual microstructure is a poor criterion for biogenicity. However, biomorphs may be distinguished from actual populations of cellular microfossils by their wide, unimodal size distribution. Biomorphs grown by diffusion in silica gel can be differentiated by their continuous gradient in size, spatial density, and morphology along the direction of diffusion.
The Little Ice Age in Iberian mountains Oliva, M.; Ruiz-Fernández, J.; Barriendos, M. ...
Earth-science reviews,
February 2018, 2018-02-00, Letnik:
177
Journal Article
Recenzirano
The Little Ice Age (LIA) is known as one of the coldest stages of the Holocene. Most records from the Northern Hemisphere show evidence of significantly colder conditions during the LIA, which in ...some cases had substantial socio-economic consequences. In this study we investigated the magnitude and timing of climate variability during the LIA in the mountains of the Iberian Peninsula, based on a wide range of natural records (including from glacial, periglacial, and lacustrine/peatland areas; fluvial/alluvial deposits; speleothems; and tree rings), historical documents, and early instrument data. The onset of the LIA commenced in approximately CE1300, and cold conditions with alternating moisture regimes persisted until approximately CE1850; the environmental responses ranged from rapid (e.g. tree rings) to delayed (e.g. glaciers). The colder climate of the LIA was accompanied by severe droughts, floods, and cold/heat waves that showed significant spatio-temporal variation across the Iberian mountains. Several phases within the LIA have been detected, including (a) 1300–1480: increasing cooling with moderate climate oscillations; (b) 1480–1570: relatively warmer conditions; (c) 1570–1620: gradual cooling; (d) 1620–1715: coldest climate period of the LIA, particularly during the Maunder Minimum, with temperatures approximately 2°C below those at present; (e) 1715–1760: warmer temperatures and a low frequency of extreme events; (f) 1760–1800: climate deterioration and more climate extremes (i.e. cold and heat waves, floods and droughts); (g) 1800–1850: highly variable climate conditions alternating with stability (1800–1815), extreme events (1815–1835), and a slight trend of warming associated with intense hydrometeorological events (1835–1850); (h) since 1850: a gradual staggered increase in temperature of approximately 1°C. Post-LIA warming has led to substantial changes in geo-ecological dynamics, mainly through shrinking of the spatial domain affected by cold climate processes.
The nuclear protein high-mobility group box 1 (HMGB1) can be passively released by necrotic cells or secreted actively by several cell types to regulate immune and inflammatory responses, as well as ...tissue remodeling. We herein aimed to characterize the effect of insulin resistance on HMGB1 in adipose tissue and to examine its potential role as a metabolic regulator in β-pancreatic cells.
Plasma HMGB1 concentration and adipose HMGB1 expression were assessed in relation to obesity and insulin resistance. Cultured adipocytes from lean and obese patients were used to investigate the intracellular distribution and factors regulating HMGB1 release, as well as to test its effects on adipogenesis and lipid metabolism. A regulatory role for HMGB1 in insulin secretion was also investigated.
Circulating HMGB1 was positively associated with body mass index, while adipose HMGB1 mRNA levels correlated with the expression of inflammatory markers. Insulin resistance modified the intracellular distribution of HMGB1 in human adipocytes, with HMGB1 being predominantly nuclear in lean and obese normoglycemic individuals while localized to the cytosol in obese patients with type 2 diabetes. Adipocytes from lean individuals exposed to conditioned media from lipopolysaccharide-stimulated macrophages induced HMGB1 redistribution to the cytoplasm and release. HMGB1 treatment had no effect on differentiation and lipid metabolism in adipocytes. However, HMGB1, whose circulating levels correlated with postload insulin concentration, increased both insulin release and intracellular Ca(2+) concentration in INS-1 cells.
These findings show, for the first time, that HMGB1 expression and release by human adipocytes is altered by inflammatory conditions as those imposed by obesity and insulin resistance. Our data reveal a novel role for HMGB1 as a stimulatory factor of insulin secretion of β-pancreatic cells.
Abstract Evaluation of specific antibody (Ab) response to polysaccharide antigens is essential for diagnosis of primary immunodeficiencies. We assessed the specific Ab responses to the ...pneumococcal-polysaccharide (PPV) and to Salmonella typhi-polysaccharide (TyphimVi) vaccines in a prospective study (EMPATHY) in patients with common variable immunodeficiency (CVID-Group, n = 22), hypogammaglobulinemia (HYPOG-Group; n = 27) and healthy controls (HC-Group; n = 16). Specific Ab concentrations in response to PPV and to TyphimVi vaccines were measured by ELISA (The Binding Site, UK), defining 3-fold increase as normal response (Ratio:3x). The RatioTyphimVi:3x was significantly greater in HC than in CVID-Group (p < 0.0001), but not than HYPOG-Group (p = 0.138). However, the RatioPPV:3x showed no significant differences among the three groups. By ROC analysis, TyphimVi better differentiated HC from CVID (AUC:0.893, IC95%: 0.791-0.996, p < 0.0001) than PPV. Our results suggest that the use of specific Ab response to TyphimVi could represent a complementary assay for the diagnosis of anti-polysaccharide Ab production deficiency in patients with CVID.
A partial-nitritation bench-scale submerged biofilter was used for the treatment of synthetic wastewater containing a high concentration of ammonium in order to study the influence of the antibiotic ...ciprofloxacin on the partial-nitritation process and biodiversity of the bacterial community structure. The influence of ciprofloxacin was evaluated in four partial-nitritation bioreactors working in parallel, which received sterile synthetic wastewater amended with 350ng/L of ciprofloxacin (Experiment 1), synthetic wastewater without ciprofloxacin (Experiment 2), synthetic wastewater amended with 100ng/L of ciprofloxacin (Experiment 3) and synthetic wastewater amended with 350ng/L of ciprofloxacin (Experiment 4). The concentration of 100ng/L of antibiotics demonstrated that the partial-nitritation process, microbial biomass and bacterial structure generated by tag-pyrosequencing adapted progressively to the conditions in the bioreactor. However, high concentrations of ciprofloxacin (350ng/L) induced a decay of the partial-nitritation process, while the total microbial biomass was increased. Within the same experiment, the bacterial community experienced sequential shifts with a clear reduction of the ammonium oxidation bacteria (AOB) and an evident increase of Commamonas sp., which have been previously reported to be ciprofloxacin-resistant. Our study suggests the need for careful monitoring of the concentration of antibiotics such as ciprofloxacin in partial-nitritation bioreactors, in order to choose and maintain the most appropriate conditions for the proper operation of the system.
•The study was done in 4 bench-scale partial-nitrification submerged bed bioreactors.•Changes in performance were studied under different antibiotic concentrations.•We focused the study on the influence of ciprofloxacin on the microbial population.•Ciprofloxacin effect in partial-nitritation was tested by multivariate analysis.
The indication for antimicrobial treatment of asymptomatic bacteriuria (AB) after kidney transplantation (KT) remains controversial. Between January 2011 and December 2013, 112 KT recipients that ...developed one episode or more of AB beyond the second month after transplantation were included in this open‐label trial. Participants were randomized (1:1 ratio) to the treatment group (systematic antimicrobial therapy for all episodes of AB occurring ≤24 mo after transplantation 53 patients) or control group (no antimicrobial therapy 59 patients). Systematic screening for AB was performed similarly in both groups. The primary outcome was the occurrence of acute pyelonephritis at 24‐mo follow‐up. Secondary outcomes included lower urinary tract infection, acute rejection, Clostridium difficile infection, colonization or infection by multidrug‐resistant bacteria, graft function and all‐cause mortality. There were no differences in the primary outcome in the intention‐to‐treat population (7.5% 4 of 53 in the treatment group vs. 8.4% 5 of 59 in the control group; odds ratio OR 0.88, 95% confidence interval CI 0.22–3.47) or the per‐protocol population (3.8% 1 of 26 in the treatment group vs. 8.0% 4 of 50 in the control group; OR 0.46, 95% CI 0.05–4.34). Moreover, we found no differences in any of the secondary outcomes. In conclusion, systematic screening and treatment of AB beyond the second month after transplantation provided no apparent benefit among KT recipients (NCT02373085).
This randomized controlled trial shows no difference in the incidence of acute pyelonephritis between kidney transplant recipients who had all their episodes of asymptomatic bacteriuria treated and those who did not receive antimicrobial treatment for asymptomatic bacteriuria beyond the second month after transplantation. See the editorial from Blumberg on page 2779.
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