Comparison of different soil organic matter fractionation methodologies: Evidences from ultrasensitive 14C measurements

Soils are studied with the aim to predict future climatic scenarios and find the best guidelines to manage terrestrial ecosystems for the mitigation of the atmospheric CO₂ rising. Carbon constituting soil organic matter (SOM) behaves as a cohort of different pools, characterized by a specific C turnover time. Both natural and anthropogenic occurring ¹⁴C reach the soil through plant littering, becoming a valid tool to trace SOM dynamics.In this study we present a series of Accelerator Mass Spectrometry (AMS) ¹⁴C measurements on SOM samples obtained by means of different laboratory protocols used for the isolation of soil pools from bulk soil (fractionation protocols). Radiocarbon signature of SOM fractions is used as a keyhole to look at the more effective fractionation procedure and comparison among measured ¹⁴C on SOM fractions revealed important indications for the proposal of a novel fractionation protocol. Our data put in evidence how particle size controls the recalcitrance of ancient SOM carbon pools.     

Gamma Rays Effects on the Optical Properties of Cerium-Doped Glasses

Optical systems employed in high-energy environments are subjected to high doses of ionizing radiation and the stability of their optical properties is required to avoid a possible failure of the experiments. Radiation hard glasses are widely used as substrates or windows in high-energy applications, due to their resistance in hostile environments where energetic particles and γ rays are present. In this work, radiation-resistant commercial glass samples were irradiated by ⁶⁰Co γ rays from 50 to 3 × 10⁵ Gy absorbed doses and at three different dose rates. The optical properties of the samples were measured to evaluate the gamma irradiation effects and the damage recovery after the end of irradiation. A dependence on the irradiation dose rates was found.     

Quadrature formulae for the positive real axis in the setting of Mellin analysis: sharp error estimates in terms of the Mellin distance

The general Poisson summation formula of Mellin analysis can be considered as a quadrature formula for the positive real axis with remainder. For Mellin bandlimited functions it becomes an exact quadrature formula. Our main aim is to study the speed of convergence to zero of the remainder for a function f in terms of its distance from a space of Mellin bandlimited functions. The resulting estimates turn out to be of best possible order. Moreover, we characterize certain rates of convergence in terms of Mellin–Sobolev and Mellin–Hardy type spaces that contain f. Some numerical experiments illustrate and confirm these results.     

An Empirical Study on the Reliability of Perceiving Correlation Indices using Scatterplots

Scatterplots have been in use for about two centuries, primarily for observing the relationship between two variables and commonly for supporting correlation analysis. In this paper, we report an empirical study that examines how humans’ perception of correlation using scatterplots relates to the Pearson's product‐moment correlation coefficient (PPMCC) – a commonly used statistical measure of correlation. In particular, we study human participants’ estimation of correlation under different conditions, e.g., different PPMCC values, different densities of data points, different levels of symmetry of data enclosures, and different patterns of data distribution. As the participants were instructed to estimate the PPMCC of each stimulus scatterplot, the difference between the estimated and actual PPMCC is referred to as an offset. The results of the study show that varying PPMCC values, symmetry of data enclosure, or data distribution does have an impact on the average offsets, while only large variations in density cause an impact that is statistically significant. This study indicates that humans’ perception of correlation using scatterplots does not correlate with computed PPMCC in a consistent manner. The magnitude of offsets may be affected not only by the difference between individuals, but also by geometric features of data enclosures. It suggests that visualizing scatterplots does not provide adequate support to the task of retrieving their corresponding PPMCC indicators, while the underlying model of humans’ perception of correlation using scatterplots ought to feature other variables in addition to PPMCC. The paper also includes a theoretical discussion on the cost‐benefit of using scatterplots.     

Boosting Direct X‐Ray Detection in Organic Thin Films by Small Molecules Tailoring

The attention focused on the application of organic electronics for the detection of ionizing radiation is rapidly growing among the international scientific community, due to the great potential of organic technology to enable large‐area conformable sensor panels. However, high‐energy photon absorption is challenging as organic materials are constituted of atoms with low atomic numbers. Here it is reported how, by synthesizing new solution‐processable organic molecules derived from 6,13‐bis(triisopropylsilylethynyl)pentacene (TIPS‐pentacene) and 2,8‐difluoro‐5,11‐bis(triethylsilylethynyl)anthradithiophene, with Ge‐substitution in place of the Si atoms to increase the material atomic number, it is possible to boost the X‐ray detection performance of organic thin films on flexible plastic substrates. Bis(triisopropylgermylethynyl)‐pentacene based flexible organic thin film transistors show high electrical performance with higher mobility (0.4 cm² V^?1 s^?1) and enhanced X‐ray sensitivity, up to 9.0 × 10⁵ µC Gy^?1 cm^?3, with respect to TIPS‐pentacene‐based detectors. Moreover, similar results are obtained for 5,11‐bis(triethylgermylethynyl)anthradithiophene devices, confirming that the proposed strategy, that is, increasing the atomic number of organic molecules by chemical tailoring to improve X‐ray sensitivity, can be generalized to organic thin film detectors, combining high X‐ray absorption, mechanical flexibility, and large‐area processing.     

Response Enhancement of Self‐Powered Visible‐Blind UV Photodetectors by Nanostructured Heterointerface Engineering

The development of efficient photodetectors (PDs) for ultraviolet (UV) light is of great importance for many applications. In this paper, a novel approach is proposed for boosting the performances of self‐powered PDs. Visible‐blind UV‐A PDs are built by combining a mesoporous TiO₂ layer with a Spiro‐OMeTAD layer. The nanostructured heterointerface is engineered by inserting a self‐assembled layer of organic modifiers. By choosing 4‐nitrobenzoic acid (NBA), the responsivity is boosted by 70% compared to the pristine devices. It achieves 64 mA W^?1 at 0 V bias, 380 nm, and 1 mW cm^?2. The PD displays a very high sensitivity (>10⁴), a fast response time (<3 ms), a high stability, and repeatability. 4‐chlorobenzoic acid, 4‐methoxy benzoic acid, 4‐nitro benzoic acid, and β‐alanine surface modifiers are studied by a combined experimental and theoretical approach. Their dipole moment is calculated. Their presence induces a step in the vacuum energy and the formed dipole field dramatically affects the charge transfer and then the photocurrent/photoresponse of the device. The higher responsivity of the NBA‐modified PD is thus explained by the better and faster electron charge transfer toward the electrical contact on TiO₂.     

Integrated PLGA–Ag nanocomposite systems to control the degradation rate and antibacterial properties

Biodegradable polymer based nanocomposite materials have attracted much attention since they can be used for biomedical and pharmaceutical applications. In order to have highly integrated PLGA nanocomposite materials, silver colloidal nanoparticles were prepared in chloroform starting from silver nitrate and using polyvinylpyrrolidone as reduction and capping agent. TEM and AFM imaging give information on the size distribution of the silver nucleus (7.0 nm) and the capping shell (8.2–10.7 nm). PLGA–Ag nanocomposites were prepared upon addition of 1 or 3% wt of silver nanoparticles to the PLGA/chloroform suspension. The effect of silver loading on polymer degradation was studied following the mass loss and the morphology of nanocomposite films at different degradation stages. The concentrations of Ag⁺, which is released during nanocomposite degradation, were monitored and analyzed through the diffusion model, to have insight on the degradation kinetics. The release rate, and likely the degradation rate, was reduced at higher silver loading. Bacterial growth tests indicated that the cell growth is inhibited in the presence of PLGA–Ag nanocomposites and the efficiency is correlated to Ag⁺ release. Thus, controlling the nanoparticle loading, a tunable degradation and antibacterial action can be designed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1185‐1193, 2013     

DNA damage, severe organ lesions and high muscle levels of As and Hg in two benthic fish species from a chemical warfare agent dumping site in the Mediterranean Sea

The aim of the present study was to evaluate the environmental threat to benthic species from chemical weapons dumped in the southern Adriatic Sea. An ecotoxicological approach using chemical analysis and biological responses was applied, in two sentinel species: the Blackbelly rosefish Helicolenus dactylopterus and European conger Conger conger. Specimen were collected in a stretch of sea, where had been dumped war materials and from a reference site free of ordnance. Residues of yperite, Hg and As were measured in fish fillets. Skin, liver, kidney and spleen were examined for histopathological and macroscopical lesions. Liver detoxifying capacities (EROD and UDPGT) and genotoxicity (comet assay) were also investigated. As and Hg levels were three-four times higher than those from the reference site in both species (p < 0.001). Both species captured in dumping site showed clear signs of chronic illness according to the health assessment index (HAI). Deep ulcers and nodules were observed on skin and external organs. Histological lesions such as periportal and bile duct fibrosis, pericholangitis, steatosis, granuloma and elevated splenic MMCs were detected in liver and spleen. Significantly higher EROD activities were also found in both species from dumping site (p < 0.01). Comet assay revealed genotoxicty in gills of C. conger from dumping site, indicating uptake of chemical warfare agents through fish gills. European conger was found to be a more sensitive bioindicator of this type of contamination than the Blackbelly rosefish.     

Prebiotic effect of soluble fibres from modern and old durum-type wheat varieties on Lactobacillus and Bifidobacterium strains

BACKGROUND: Wheat grains are a rich source of dietary fibres, particularly in the western human diet. Many of the health effects attributed to dietary fibres are believed to be related to their microbial fermentation in the gut. This study evaluated the ability of two potentially probiotic strains, Lactobacillus plantarum L12 and Bifidobacterium pseudocatenulatum B7003, to ferment soluble dietary fibres (SDFs) from modern and ancient durum‐type wheat grains. RESULTS: Fibre microbial utilisation was highly variable and dependent on the strain. SDFs from the varieties Svevo and Solex supported the growth of L. plantarum L12 the best, whereas those from the varieties Anco Marzio, Solex and Kamut^® Khorasan were good carbohydrate substrates for B. pseudocatenulatum B7003. The highest prebiotic activity scores (describing the extent to which prebiotics support selective growth of probiotics) for B7003 were obtained with SDFs from the varieties Solex (0.57), Kamut^® Khorasan (0.56) and Iride (0.55), whereas for L12 the highest scores were achieved with the varieties Orobel (0.63), Kamut^® Khorasan (0.56) and Solex (0.53). CONCLUSION: The present study has identified some SDFs from durum‐type wheat grains as suitable prebiotic substrates for the selective proliferation of B. pseudocatenulatum B7003 and L. plantarum L12 in vitro. The results provide the basis for the potential utilisation of wheat‐based prebiotics as a component of synbiotic formulations. Copyright © 2012 Society of Chemical Industry