Stand age, degree of encroachment and soil characteristics modulate changes of C and N cycles in dry grassland soils invaded by the N2-fixing shrub Amorpha fruticosa.

The N2-fixing shrub Amorpha fruticosa L. is rapidly spreading in the dry riparian natural grasslands of Europe, altering ecosystem functions and depleting plant diversity. Alteration of the N cycle represents the key factor involved in invasions by N2-fixing plants with cascading effects on plant species richness. We hypothesized that A. fruticosa encroachment strongly impacts not only the N but also the C cycle and that the magnitude of such alterations may be modulated by soil characteristics. To test these hypotheses, we selected four river floodplains in North East of Italy and compared natural uninvaded grasslands with half invaded and completely invaded sites, based on A. fruticosa stand characteristic and relevant leaf traits and on soil properties related to soil texture and to C and N cycles. Soil organic matter mineralisation, ammonification and nitrification rates were determined. Soil nitrification increased remarkably with plant invasion while ammonification was significantly higher only in half invaded sites. Soil organic matter mineralisation, microbial biomass C sustained per soil organic C unit and nitrification positively correlated with stand age, regardless to the stage of the encroachment. Mineralisation and nitrification increased with soil organic C and total N in uninvaded and completely invaded sites, but decreased in half invaded sites. At the half invasion stage, trends in nitrification and CO2 mineralisation were transitionally reverted and remediation may be facilitated by less pronounced changes in soil properties compared to completely invaded sites. Direct effects of plant invasion are modulated by the action of soil characteristics such as soil organic C and clay contents, with soils rich in organic C showing larger nitrification and mineralisation rates.

Bioaccumulation of polycyclic aromatic hydrocarbons and survival of earthworms (Eisenia andrei) exposed to biochar amended soils.

Biochar has a charcoal polycyclic aromatic structure which allows its long half-life in soil, making it an ideal tool for C sequestration and for adsorption of organic pollutants, but at the same time raises concerns about possible adverse impacts on soil biota. Two biochars were tested under laboratory-controlled conditions on Eisenia andrei earthworms: a biochar produced at low temperature from wine tree cuttings (WTB) and a commercial low tar hardwood lump charcoal (HLB). The avoidance test (48-h exposure) showed that earthworms avoid biochar-treated soil with rates higher than 16 t ha(-1) for HLB and 64 t ha(-1) for WTB. After 42 days, toxic effects on earthworms were observed even at application rates (100 t ha(-1)) that are generally considered beneficial for most crops. The concentration of HLB and WTB required to kill half of earthworms' population (LC50; 95% confidence limits) in the synthetic OECD soil was 338 and 580 t ha(-1), respectively. Accumulation of polycyclic aromatic hydrocarbons (PAH) in earthworms exposed to the two biochar types at 100 t ha(-1) was tested in two soils of different texture. In biochar-treated soils, the average earthworm survival rates were about 64% in the sandy and 78% clay-loam soils. PAH accumulation was larger in the sandy soil and largest in soils amended with HLB. PAH with less than four rings were preferentially scavenged from the soil by biochars, and this behaviour may mask that of the more dangerous components (i.e. four to five rings), which are preferentially accumulated. Earthworms can accumulate PAH as a consequence of exposure to biochar-treated soils and transfer them along the food chain. Soil type and biochar quality are both relevant in determining PAH transfer.

Liquid crystal quenched orientational disorder at an AFM-scribed alignment surface.

A polyimide substrate was scribed using the stylus of an atomic force microscope, then covered with a nematic liquid crystal. The fiber from a near field scanning optical microscope was immersed into the liquid crystal and rastered approximately 80 nm above the surface, thereby obviating smearing effects that occur in thicker samples. By appropriate averaging of multiple data sets, a histogram of the "frozen-in" director deviation Δφ from the average easy axis was obtained, having a full-width-half-maximum of ∼0.02 rad. Additionally, the spatial autocorrelation function of Δφ was extracted, where the primary correlation length was found to be comparable to, but larger than, the liquid crystal's extrapolation length. A secondary characteristic length scale of a few µm was observed, and is thought to be an artifact due to material ejection during the scribing process. Our results demonstrate the utility of nanoscale imaging of the interface behavior inside the liquid crystal.

Performance of alginate films for retention of L-(+)-ascorbic acid.

In view of acting as controlled delivery systems for nutritional supplementation, therapy or antioxidant activity at interfaces, alginate films of different copolymer composition and glycerol plasticizer levels were developed in the presence of Ca(2+) for achieving higher stability of L-(+)-ascorbic acid (AA). The ability of the alginate network to preserve AA from hydrolysis, tested by storage under vacuum at 25 °C, only decreased with the relative humidity (RH) increase when alginates were mainly constituted by guluronic-guluronic acid blocks (GG), whereas also decreased with the glycerol level increase when mannuronic-mannuronic acid (MM) and/or alternating guluronic-mannuronic (GM+MG) flexible blocks were present in higher proportions. This result could be probably related to the lower capability of the latter alginate block compositions to immobilize water in the network as they are not able to constitute Ca(2+) mediated junction zones where water molecules are highly retained. Films also studied under air storage showed that even at less favorable conditions of RH and glycerol levels, both GG and GM+MG enriched alginate networks in general preserved AA from oxidation. It also demonstrated that hydrolysis is the principal way by which AA is lost when supported in films.

The interaction of humic substances with the human prion protein fragment 90-231 affects its protease K resistance and cell internalization.

In this paper we analyzed the determinants and the structural effects of the interaction of human prion protein fragment 90-231 (HuPrP) with humic substances, (HS) including humic (HA) and fulvic (FA) acids, natural refractory organic polyanions widely diffused in soils and waters. We show that this interaction is mainly driven by non-specific electrostatic attraction involving regions situated within alpha-helix A and beta-sheet S1 of human PrP. FA binding to HuPrP altered its ability to acquire some PrPSc-like characteristics induced by the mild thermal denaturation of the peptide (1 h at 53 degrees C). In particular, in the presence of FA, HuPrP shows a reduced amount of beta-sheet content (as demonstrated by the reduced binding of thioflavin T), an increased sensitivity to protease K and an inhibition of the entering in the fibrillogenic pathway. FA/HuPrP interaction caused the aggregation of the peptide in unstructured macrocomplexes, as demonstrated by the altered electrophoretic migration in semi-denaturing detergent-agarose gel assay. Importantly, in the presence of FA the rate of internalization of HuPrP in human neuroblastoma cells was significantly reduced as compared to that of the beta-structured peptide. Therefore, HS inhibited the acquisition of PrP(Sc)-like structural properties that, in turn, are responsible for HuPrP intracellular accumulation and lead to neuronal death. Important implications of these data are that HuPrP-HS complexes, being unable to be internalized in living cells may represent a molecular mechanism for the reduced transmission of prion transmission from HS-rich soil also in the presence of contamination from infected animals.

The mineralisation of fresh and humified soil organic matter by the soil microbial biomass.

Soil organic matter comprises all dead plant and animal residues, from the most recent inputs to the most intensively humified. We have found that traces of fresh substrates at microg g(-1) soil concentrations (termed 'trigger molecules') activate the biomass to expend more energy than is contained in the original 'trigger molecules'. In contrast, we suggest that the rate limiting step in soil organic matter mineralisation is independent of microbial activity, but is governed by abiological processes (which we term the Regulatory Gate theory). These two findings have important implications for our understanding of carbon mineralisation in soil, a fundamental process in the sequestration of soil organic matter.

Assessment of chemical and biochemical stabilization of organic C in soils from the long-term experiments at Rothamsted (UK).

Biological and chemical stabilization of organic C was assessed in soils sampled from the long-term experiments at Rothamsted (UK), representing a wide range of carbon inputs and managements by extracting labile, non-humified organic matter (NH) and humic substances (HS). Four sequentially extracted humic substances fractions of soil organic matter (SOM) were extracted and characterized before and after a 215-day laboratory incubation at 25 degrees C from two arable soils, a woodland soil and an occasionally stubbed soil. The fractions corresponded to biochemically stabilised SOM extracted in 0.5M NaOH (free fulvic acids (FA) and humic acids (HA)) and chemically plus biochemically stabilised SOM extracted from the residue with 0.1M Na4P2O7 plus 0.1M NaOH (bound FA and HA). Our aim was to investigate the effects of chemical and biochemical stabilization on carbon sequestration. The non-humic to humic (NH/H) C ratio separated the soils into two distinct groups: arable soils (unless fertilised with farmyard manure) had an NH/H C ratio between 1.05 and 0.71, about twice that of the other soils (0.51-0.26). During incubation a slow, but detectable, decrease in the NH/H C ratio occurred in soils of C input equivalent or lower to 4Mgha(-1)y(-1), whereas the ratio remained practically constant in the other soils. Before incubation the free to bound humic C ratio increased linearly (R2=0.91) with C inputs in the soils from the Broadbalk experiment and decreased during incubation, showing that biochemical stabilization is less effective than chemical stabilization in preserving humic C. Changes in delta13C and delta15N after incubation were confined to the free FA fractions. The delta13C of free FA increased by 1.48 and 0.80 per thousand, respectively, in the stubbed and woodland soils, indicating a progressive biological transformation. On the contrary, a decrease was observed for the bound FA of both soils. Concomitantly, a Deltadelta15N of up to +3.52 per thousand was measured after incubation in the free FA fraction and a -2.58 Deltadelta15N in the bound FA. These changes, which occurred during soil incubation in the absence of C inputs, indicate that free FA fractions were utilised by soil microorganisms, and bound FA were decomposed and replaced, in part, by newly synthesized FA. The 13CPMAS-TOSS NMR spectra of free HA extracted before and after 215 days of incubation were mostly unchanged. In contrast, changes were evident in bound HA and showed an increase in aromatic C after incubation.

Possible model of an antiferroelectric twist grain boundary phase.

Using x-ray and optical methods we have probed the structural organization of an antiferroelectric twist grain boundary phase (TGBC(a)) lying between the regular antiferroelectric smectic-C (SmC(a)* and the smectic-Q (SmQ) or isotropic phase. We find that the twist axis is everywhere perpendicular to the local smectic layer normal and that the helical superstructure is incommensurate with the smectic layer structure. The twist grain boundaries consist of a periodic lattice of alternating +1/2 and -1/2 dispirations, i.e., unit screw dislocations in combination with half unit disclinations. The molecular tilt plane is alternatingly parallel and perpendicular to the twist axis. We find that the optically measured tilt angle in the SmC(a)* phase is smaller than that measured by x rays, which is the opposite to what is found in the SmC* phase. This means that the core part tilts less than the end chains in the SmC(a)* phase, while it tilts more in the SmC* phase. On entering the TGB phase a clear decrease is measured in the tilt angle. This is explained by the elastic influence from the disclinations, which appear in this phase.

Two fluid-structure approaches for 3D simulation of St. Jude Medical bileaflet valve opening.

This paper deals with the three-dimensional (3D) numerical simulation of the opening transient for a bileaflet mechanical heart valve (St. Jude Medical Hemodynamic Plus, 27 mm characteristic size). The discussion concerns two different types of ""partitioned"" fluid-structure models, with weak and strong coupling. Both approaches are based on a moving deforming mesh method as implemented in the CFD commercial software Fluent (Fluent Inc., USA), and both yielded dynamically consistent results from a quantitative viewpoint. There is a slight improvement (peak relative difference <1%) of the numerical solution (angles vs. time) when using the strong instead of the weak coupling model. This is of utmost importance when the considerable reduction of the computational costs for the weak scheme (about 60% less) is taken into account. However, the strong coupling model provides a more consistent physical description of the interaction when looking at small-scale features like stress close to geometrical singularities. In the experiments, the differences both in terms of time-to-peak delay (15% of the opening time) and in terms of underestimation of the peak velocity (8%) seemed due to defects in the fluid inertia assessment, which depends on initial and boundary data.

Brownian motion of an ellipsoid.

We studied the Brownian motion of isolated ellipsoidal particles in water confined to two dimensions and elucidated the effects of coupling between rotational and translational motion. By using digital video microscopy, we quantified the crossover from short-time anisotropic to long-time isotropic diffusion and directly measured probability distributions functions for displacements. We confirmed and interpreted our measurements by using Langevin theory and numerical simulations. Our theory and observations provide insights into fundamental diffusive processes, which are potentially useful for understanding transport in membranes and for understanding the motions of anisotropic macromolecules.

A 2D spring model for the simulation of ultrasonic wave propagation in nonlinear hysteretic media.

A two-dimensional (2D) approach to the simulation of ultrasonic wave propagation in nonclassical nonlinear (NCNL) media is presented. The approach represents the extension to 2D of a previously proposed one dimensional (1D) Spring Model, with the inclusion of a PM space treatment of the intersticial regions between grains. The extension to 2D is of great practical relevance for its potential applications in the field of quantitative nondestructive evaluation and material characterization, but it is also useful, from a theoretical point of view, to gain a better insight of the interaction mechanisms involved. The model is tested by means of virtual 2D experiments. The expected NCNL behaviors are qualitatively well reproduced.

Cracks and topological defects in lyotropic nematic gels.

We report on the effects of the coupling of nematic order and elasticity in anisotropic lyotropic gels consisting of large nematic domains of surfactant coated single wall carbon nanotubes embedded in a cross-linked N-isopropyl acrylamide polymer matrix. We observe the following striking features: (i) undulations and then cusping of the gel sidewalls, (ii) a nematic director field that evolves as the gel sidewalls deform, (iii) networks of surface cracks that are orthogonal to the nematic director field, and (iv) fissures at the sidewall cusps and associated topological defects that would not form in liquid nematics.

Dynamics of nematic liquid crystal disclinations: the role of the backflow.

We measure the electric-field-driven annihilation of nematic disclination pairs with strength +/- 1/2 in the 4-cyano-4'-n-pentylbiphenyl (5CB) liquid crystal. The use of a very weak azimuthal anchoring ensures a two-dimensional director field. The relaxation is governed by the formation of a pi wall connecting the two opposite charge defects. The +1/2 disclinations move almost twice as fast as the -1/2 disclinations. The simple used geometry allows a quantitative comparison with numerical studies based on the hydrodynamics of the tensorial order parameter. The simulations show that in the pi wall regime the symmetry breaking is due to the backflow and not to the elastic anisotropy.

[Uncommon etiology of acute abdomen in pediatric age: the torsion of spleen]. / Una causa non comune di addome acuto in età pediatrica: la torsione splenica.

The torsion of spleen on its vascular shank represents an uncommon problem, responsible of acute and chronic pain. The mobile spleen is fixed only through hilus vessels the gastrosplenic ligament. The incidence is unknow, greater in the male with an M:F ratio 6.1 in the first ten years of life, even if an episode of intrauterine torsion has been reported. The diagnosis can be performed with ultrasonography, angiography, scintigraphy and CT scan. There are reported two cases: male of 2.5 years female of 14 years who presented with recurrent pain to the left side, vomit diarrhoea and fever. Objectively a palpable mass was present. Ultrasonography and angio-CT scan of abdomen revealed splenomegaly, ptosis of the spleen and malrotation with signs of obstruction of the vessels. The treatment in both cases was splenectomy. The spleen appeared rotated on its shank and increased of volume, deprived of anatomical structures of fixation. The histological report confirmed the haemorrhagic infarction. The excessive mobility of the spleen, from insufficiency or absence of the ligamentous attachments is case of abdominal pain or acute abdomen, that can complicate with the infarction of the spleen. Angio-CT scan, in the cases here reported, has shown to greater sensibility in comparison to the ultrasonography. The Authors believe that the video-laparoscopic splenopexy, when the diagnosis is made of "wandering spleen" with painful repeated episodes, can be finalized, to the preservation of organ.

Progesterone supplement in pregnancy: an immunologic therapy?

One of the most interesting functions of the placenta is the regulation of the maternal immune response such that the fetal semi-allograft is tolerated during pregnancy. Trophoblasts are presumed to be essential to this phenomenon because they lie at the maternal-fetal interface, where they are in direct contact with cells of the maternal immune system. Trophoblasts do not express classic major histocompatibility complex (MHC) class II molecules. Surprisingly, cytotrophoblasts express more HLA-G, a MHC class Ib molecule, as they invade the uterus. Progesterone plays an important role in postovulatory regulation of the menstrual cycle. If fertilization occurs, progesterone supports implantation of the ovum and maintains the pregnancy. Progesterone has been named the 'hormone of pregnancy', because in preparing the endometrium for embryo implantation and facilitating endometrial development, it is critical to the very survival of a pregnancy. In addition, this key hormone inhibits the rejection of T cell-mediated tissue and also decreases myometrial activity and sensitivity throughout pregnancy. The cellular actions of progesterone are mediated through intracellular progesterone receptors (PRs), which are well studied gene regulators, not express classic major histocompatibility complex. The more used paradigm is relative to the alteration of relationship TH1/TH2, but the complexity of the respective distributions of cytokines at the materno-fetal interface, strongly suggest that, as useful as it certainly was for a while, the Th1/Th2 paradigm must now be considered as an oversimplification. Rather, the existing data point to sequential windows and are suggestive of a system where an extreme complexity is allied to very precise timing and tuning. They also suggest that the materno-fetal relationship is not simply maternal tolerance of a foreign tissue, but a series of intricate mutual cytokine interactions governing selective immune regulation and also control of the adhesion and vascularization processes during this dialogue. However, as shifting the immune response toward the Th2 pattern (IL-4, IL-5, IL-6) may benefit the fetus, whereas development of proinflammatory Th1 cells (secreting IL-2, IFN g, TNF a) may be harmful. Now we are working to open comprise the precise behaviour of NK populations, with the hope of obtaining a diagnostic test of the condition of abortion from 'immunological causes'.

Land application of biosolids. Soil response to different stabilization degree of the treated organic matter.

The effect of land application of biosolids on an agricultural soil was studied in a 2-month incubation experiment. The soil microbial biomass and the availability of heavy metals in the soil was monitored after the application of four different composting mixtures of sewage sludge and cotton waste, at different stages of composting. Land application caused an increase of both size and activity of soil microbial biomass that was related to the stabilization degree of the composting mixture. Sewage sludge stabilization through composting reduced the perturbance of the soil microbial biomass. At the end of the experiment, the size and the activity of the soil microbial biomass following the addition of untreated sewage sludge were twice those developed with mature compost. For the mature compost, the soil microbial biomass recovered its original equilibrium status (defined as the specific respiration activity, qCO2) after 18 days of incubation, whereas the soil amended with less stabilized materials did not recover equilibrium even after the two-month incubation period. The stabilization degree of the added materials did not affect the availability of Zn, Ni, Pb, Cu, Cr and Cd in the soil in the low heavy metal content of the sewage sludge studied. Stabilization of organic wastes before soil application is advisable for the lower perturbation of soil equilibria status and the more efficient C mineralization.

Azimuthal anchoring energy at the interface between a nematic liquid crystal and a PTFE substrate.

The azimuthal anchoring energy of the nematic liquid crystal 4-pentyl-4'-cyanobiphenil (5CB) on a poly(tetrafluoroethylene) (teflon, PTFE) film is measured for the first time. The PTFE film is deposed using the Wittmann and Smith technique which consists on rubbing a bar of this polymer against a glass substrate at a controlled temperature and pressure. Measurements of the azimuthal anchoring energy are made with a reflectometric technique which provides high accuracy and sensitivity. The dependence of the azimuthal anchoring energy on temperature and on the rubbing pressure is investigated. The extrapolation length remains virtually constant in the whole temperature range of the nematic phase except for an increase of 25% close to the clearing temperature. The azimuthal anchoring energy is somewhat strong and increases with increasing the deposition pressure of PTFE. The observation of a relevant pre-transitional anisotropy of the reflection coefficients in the isotropic phase proves that the surface interactions favor an excess of orientational order. Ageing of the anchoring energy and gliding of the easy axis are experimentally observed. Both these phenomena suggest the presence of an anisotropic adsorbed layer of nematic molecules on the PTFE film.

Anchoring screening of defects interaction in a nematic liquid crystal.

The relaxation dynamic of a dipole of +1/2 and -1/2 parallel disclination lines in a confined geometry is measured. The confinement and the planar anchoring conditions force the disclinations to be normal to the glass plates. In a first asymptotic regime, the direct elastic interaction between disclination is completely screened out by the anchoring energy. In a second regime, corresponding to the final annihilation steps, the dynamic follows the square-root law predicted by de Gennes for two isolated and parallel disclinations. The annihilation dynamic, in the asymptotic regime, is in good agreement with an elastic model based on an electrostatic analogy.

[Esophageal atresia and tracheoesophageal fistula: personal contribution]. / Atresia esofagea e fistola tracheoesofagea: contributo personale.

From January 1988 to December 1999, 21 new born babies, 13 boys and 8 girls, with esophageal atresia (EA) and tracheosophageal fistula (TEF) were treated at Division of Pediatric Surgery in Foggia (Italy). At birth their weight ranged from 1.600 to 3.000 g, the gestional age ranged from 36 to 41 weeks. Five (23%) of them were premature, seven (58%) SGA, seventeen (80%) associated congenital anomalies. Complete surgical correction was performed in all patients. In three AE cases with wide-gap an azygos vein flap was used to strengthen the anastomosis under excessive tension. The pathogenetic factors involved in these complications such as leak, stricture (stenosis), recurrent TEF and gastro-esophageal reflux are (are taken into account) and analysed. No baby died owing to anastomatic complication. Survival rate was 100% in Montreal I and 83% in Montreal II. A new born baby died but his death was due to major associated conenital anomalies and not to surgical complications. The Authors believe that the azygos vein flap is a useful technique in the treatment of esophageal atresia wide-gap.