High resolution spectroscopy of the three dimensional cosmic web with close QSO groups

We study the three-dimensional distribution of matter at z~2 using high resolution spectra of QSO pairs and simulated spectra drawn from cosmological hydro-dynamical simulations. We present a sample of 15 QSOs, corresponding to 21 baselines of angular separations evenly distributed between ~1 and 14 arcmin, observed with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the European Southern Observatory-Very Large Telescope (ESO-VLT). The observed correlation functions of the transmitted flux in the HI Lya forest transverse to and along the line of sight are in agreement, implying that the distortions in redshift space due to peculiar velocities are relatively small and - within the relatively large error bars - not significant. The clustering signal is significant up to velocity separations of ~300 km/s, corresponding to about 5 h^{-1} comoving Mpc. Compatibility at the 2 sigma level has been found both for the Auto- and Cross-correlation functions and for the set of the Cross correlation coefficients. The analysis focuses in particular on two QSO groups of the sample. Searching for alignments in the redshift space between Lya absorption lines belonging to different lines of sight, it has been possible to discover the presence of a wide HI structures extending over about ten Mpc in comoving space, and give constraints on the sizes of two cosmic under-dense regions in the intergalactic medium.Comment: Accepted by MNRAS, version matching the published on

Dissecting the effects of free fatty acids on the thermodynamic stability of complex model membranes mimicking insulin secretory granules

A stepwise micro-DSC study of Small, Large and Giant Unilamellar Vesicles prepared as pure and mixed systems of DMPC, DPPC, DSPC and DOPC was performed, achieving the preparation of final model membranes whose phospholipid compositions represent the 75% in terms of the phospholipids tails and the 50% headgroups of the Insulin Secretory Granules (vesicles located in the pancreatic Langerhans \u3b2-cells and which are responsible for insulin and amylin storage and secretion in response to nutrient intake). Moreover, the effect of Free Fatty Acids, whose levels are recurrently altered in diabetic and/or obese subjects, on the thermodynamic stability of the final membranes was eventually investigated. The results allowed to discriminate each single thermodynamic contribution among the main factors that dictate the overall thermodynamic stability of these complex unilamellar systems evidencing mainly entropic effects hierarchically summarized as phospholipid unsaturations > phospholipid tail length > membrane curvature. The effect of the Free Fatty Acids highlighted a strong stabilizing effect on the membranes as well as more pronounced phase segregations in the case of saturated acids (palmitic and stearic), whereas the opposite effect was observed in the case of an unsaturated one (oleic)

Entropy-based measure of structural order in water

We analyze the nature of the structural order established in liquid TIP4P water in the framework provided by the multi-particle correlation expansion of the statistical entropy. Different regimes are mapped onto the phase diagram of the model upon resolving the pair entropy into its translational and orientational components. These parameters are used to quantify the relative amounts of positional and angular order in a given thermodynamic state, thus allowing a structurally unbiased definition of low-density and high-density water. As a result, the structurally anomalous region within which both types of order are simultaneously disrupted by an increase of pressure at constant temperature is clearly identified through extensive molecular-dynamics simulations.Comment: 5 pages, 2 figures, to appear in Phys. Rev. E (Rapid Communication

Probing 3-D matter distribution at z~2 with QSO multiple lines of sight

We investigate the 3-D matter distribution at z~2 with high resolution (R ~ 40000) spectra of QSO pairs and groups obtained with the UVES spectrograph at ESO VLT. Our sample is unique for the number density of objects and the variety of separations, between 0.5 and 7 proper Mpc. We compute the real space cross-correlation function of the Lyman-alpha forest transmitted fluxes. There is a significant clustering signal up to ~2 proper Mpc, which is still present when absorption lines with high column density (log N > 13.8) are excluded.Comment: Poster paper presented at the IAU Colloquium #199 on "Probing Galaxies through Quasar Absorption Lines" held in Shanghai, China from March 14th to 18th, 200

Tomography of the intergalactic medium with Ly-alpha forests in close QSO pairs

We study the three-dimensional distribution of non virialised matter at z~2 using high resolution spectra of QSO pairs and simulated spectra drawn from cosmological hydrodynamical simulations. We have collected the largest sample of QSO pairs ever observed with UVES at the ESO-VLT, with angular separations between ~1 and 14 arcmin. The observed correlation functions of the transmitted flux in the HI Lyman alpha forest along and transverse to the lines of sight are in good agreement implying that the distortions in redshift space due to peculiar velocities are small. The clustering signal is significant up to velocity separations of ~200 km/s, or about 3 h^{-1} comoving Mpc. The regions at lower overdensity (rho/ < 6.5) are still clustered but on smaller scales (Delta v < 100 km/s). The observed and simulated correlation functions are compatible at the 3 sigma level. A better concordance is obtained when only the low overdensity regions are selected for the analysis or when the effective optical depth of the simulated spectra is increased artificially, suggesting a deficiency of strong lines in the simulated spectra. We found that also a lower value of the power-law index of the temperature-density relation for the Lyman alpha forest gas improves the agreement between observed and simulated results. If confirmed, this would be consistent with other observations favouring a late HeII reionization epoch (at z~3). We remark the detection of a significant clustering signal in the cross correlation coefficient at a transverse velocity separation Delta v_{\perp} ~500 km/s whose origin needs further investigation.Comment: Accepted for publication in MNRAS, revised version matching the accepted on

Formation of p-n junction in polymer electrolyte-top gated bilayer graphene transistor

We show simultaneous p and n type carrier injection in bilayer graphene channel by varying the longitudinal bias across the channel and the top gate voltage. The top gate is applied electrochemically using solid polymer electrolyte and the gate capacitance is measured to be 1.5 $\mu F/cm^2$, a value about 125 times higher than the conventional SiO$_2$ back gate capacitance. Unlike the single layer graphene, the drain-source current does not saturate on varying the drain-source bias voltage. The energy gap opened between the valence and conduction bands using top and back gate geometry is estimated.Comment: 16 pages, 6 figure

Metabolic risk of new food technologies: calorimetric study of model cell membranes for the determination of the influence of free fatty acids (FFA) in diabetes mellitus onset

Type 2 diabetes mellitus (T2DM) is a chronic disease that continues to spread in both developed and developing countries. Indeed, the individuals affected by diabetes mellitus (type 1 and type 2) in the world are now close to 400 million and estimates suggest that they will reach 600 million by 2035. The rapid spreading of this disorder is influenced not only by genetic factors but also by environmental ones: socio-economic variations, evolution of lifestyle and changes in dietary habits have contributed to increase the percentage of overweight and obese individuals, which in turn have led to a greater diffusion of diabetes. In fact, weight gain is closely related to insulin-resistance onset, which is considered as the starting point for the development of the disease. However, the manner in which obesity and nutrition factors are linked to the onset of T2DM is not fully understood yet, especially at a molecular level. The aim of the project presented here is to prepare and characterize (thermodynamically and spectroscopically) model membranes which simulate as possible the phospholipid bilayers of the Langerhans \u3b2-cells in order to highlight and discriminate the role of the lipid composition and foodborne stress (in terms of [Ca2+] and [FFA]) in the membrane stability. Moreover, the interaction between the model membrane and hIAPP, which seems to be involved in \u3b2-cells death, will be used to evaluate the influence of membrane stability on T2DM onset

Thermodynamic stability of complex model membranes: the role of composition, morphology and food fatty acids

Free Fatty Acids (FFAs) have been shown to be involved in several membrane-mediated cellular processes as lipid-assisted protein transport across the bilayer, fusion of lipid vesicles/cells and signalling for several cell mechanisms (e.g. insulin secretion). However, altered plasma FFAs levels typical of obese and/or diabetic subjects have been proposed to contribute to the onset and progression of type 2 diabetes mellitus through both their possible involvement in altered metabolic pathways and their direct action on cell membranes. Moreover, the action of FFAs has also been hypothesized to play a role in the interaction of amylin, an amyloidogenic protein, with cell membranes likely leading to the pancreatic \u3b2-cells failure by apoptosis. Among several studies highlighting the FFAs-membrane interaction by means of spectroscopic, imaging, molecular dynamics and/or theoretical approaches, few works are devoted to a thermodynamic characterization of the role of FFAs on the overall membrane stability, however without considering the compositional and morphological complexity of real biological vesicles. In such a frame, the present work was aimed at the calorimetric investigation of small, large and giant unilamellar vesicles prepared as pure and mixed systems of phospholipids with different length and unsaturation level. The preparation of a final model membrane was finally achieved mimicking the phospholipid bilayer of Insulin Secretory Granules (ISGs), vesicles located in the pancreatic Langerhans \u3b2-cells and which are responsible for insulin and amylin storage and secretion in response to nutrients intake. This study was performed through micro-DSC and allowed to discriminate each single thermodynamic contribution among the main factors that dictate the overall thermodynamic stability of these complex unilamellar systems (phospholipid unsaturations > phospholipid tail length > membrane curvature). The effect of three different FFAs, such as palmitic, stearic and oleic acids, added in different percentages both to a completely saturated ternary model membrane and to an unsaturated one (i.e. the final model membrane made by the saturated one including the 5% of 1,2-dioleoyl-sn-glycero-3-phosphocholine, DOPC) was eventually investigated highlighting a strong stabilizing effect as well as more pronounced phase segregations in the case of saturated acids, whereas the opposite effect was observed in the case of unsaturated FFAs. Moreover, the stabilizing effects deriving from saturated FFAs were more pronounced in less stable membranes, i.e. the unsaturated one, whereas the destabilizing effects deriving from the unsaturated FFAs were more pronounced in more stable membranes, i.e. the completely saturated one

Performance of Pheromone-Baited Traps to Monitor the Seasonal Abundance of Tortrix Moths in Chestnut Groves.

(1) Background: Pammene fasciana (L.), Cydia fagiglandana (Zeller), and C. splendana (H&uuml;bner) (Lepidoptera: Tortricidae) are considered key moth pests of chestnut in Europe. (2) Methods: Investigations were performed in 2018&ndash;2019 in northern Italy. Sticky traps and commercially available pheromones were used for monitoring; moreover, two experimental pheromone blends were tested. All specimens were identified according to male genitalia and molecular analyses. Newly formed chestnut husks and fruits were randomly collected to evaluate the presence of larvae and/or feeding damage, by comparing it to trap catches. (3) Results: P. fasciana was present in all the sites, whereas Cydia species were recorded in three sites of six, with differences in abundance related to pheromone blends studied. Several non-target species, such as Oegoconia novimundi (Busck) and Cydia ilipulana (Walsingham), were present. Data about the seasonal flight activity are provided. (4) Conclusions: This research contributes to ascertaining the presence and abundance of tortrix moths in Italian chestnut groves, and the presence of non-target species highlights the risk of overestimating catches. Fruit damage recorded did not always reflect catches made by pheromone traps, suggesting that monitoring may underestimate the real size of moths&rsquo; populations. All of the data acquired are important for planning specific control measures