Experimental Evidence For Self-Similar Structures In The Aggregation Of Porphyrins In Aqueous Solutions

We have studied the aggregation of the porphyrin t-H₂Pagg in aqueous solution by light scattering. The intensity profile of the elastically scattered light, studied in the exchanged wave-vector range 0.2 ≤ q ≤ 31.4 μ m⁻¹, indicates that the aggregation produces large monodisperse clusters having a fractal structure, and is driven by diffusion-limited aggregation kinetics. Additional measurements performed at different q values confirm such a picture giving a hydrodynamic radius R(H) consistent with the radius of gyration R(g) measured by elastic scattering. This is explained taking into account the q² dependence observed in the mean decay rate of the intensity-intensity correlation function and the effect on this latter dynamical quantity of anisotropies in the cluster structure

Surface-enhanced Raman scattering of SnO2_{2} bulk material and colloidal solutions

Surface enhanced Raman scattering (SERS) effects on tin dioxide in the form of bulk material, nanostructured thin films and colloidal solutions were investigated. Raman spectra are characterized by the three Raman scattering peaks at 478, 633, and 776 \invcm, assigned to the E$_g$, A$_{1g}$ and B$_{2g}$ modes, typical of rutile SnO$_2$. In presence of the silver nanoparticles, in addition to the enhancement intensity of some of the fundamental tin dioxide rutile Raman features, the appearance of a new Raman scattering peak at about 600 cm$^{-1}$ is observed. This spectral features is observed, in presence of silver nanoparticles, also in other SnO$_2$ based system such as pulsed laser deposited thin films, with different stoichiometry, and in water colloidal solutions. The observed SERS effects are explained in terms of electric-field gradient mechanism that are generated near a metal surface. In particular, the appearance of a peak near 600 \invcm is attributed to the Raman activation of the infrared E$_u$ transverse optical (TO) mode.Comment: 7 pages, 6 figure

Gene-drive suppression of mosquito populations in large cages as a bridge between lab and field.

CRISPR-based gene-drives targeting the gene doublesex in the malaria vector Anopheles gambiae effectively suppressed the reproductive capability of mosquito populations reared in small laboratory cages. To bridge the gap between laboratory and the field, this gene-drive technology must be challenged with vector ecology.Here we report the suppressive activity of the gene-drive in age-structured An. gambiae populations in large indoor cages that permit complex feeding and reproductive behaviours.The gene-drive element spreads rapidly through the populations, fully supresses the population within one year and without selecting for resistance to the gene drive. Approximate Bayesian computation allowed retrospective inference of life-history parameters from the large cages and a more accurate prediction of gene-drive behaviour under more ecologically-relevant settings.Generating data to bridge laboratory and field studies for invasive technologies is challenging. Our study represents a paradigm for the stepwise and sound development of vector control tools based on gene-drive

Stabilization of mid-sized silicon nanoparticles by functionalization with acrylic acid

We present an enhanced method to form stable dispersions of medium-sized silicon nanoparticles for solar cell applications by thermally induced grafting of acrylic acid to the nanoparticle surface. In order to confirm their covalent attachment on the silicon nanoparticles and to assess the quality of the functionalization, X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier spectroscopy measurements were carried out. The stability of the dispersion was elucidated by dynamic light scattering and Zeta-potential measurements, showing no sign of degradation for months

Time-of-Flight Neutron Imaging on IMAT@ISIS: A New User Facility for Materials Science

The cold neutron imaging and diffraction instrument IMAT at the second target station of the pulsed neutron source ISIS is currently being commissioned and prepared for user operation. IMAT will enable white-beam neutron radiography and tomography. One of the benefits of operating on a pulsed source is to determine the neutron energy via a time of flight measurement, thus enabling energy-selective and energy-dispersive neutron imaging, for maximizing image contrasts between given materials and for mapping structure and microstructure properties. We survey the hardware and software components for data collection and image analysis on IMAT, and provide a step-by-step procedure for operating the instrument for energy-dispersive imaging using a two-phase metal test object as an example

Bilingualism in university students: further evidence of metalinguistic benefits

This empirical study aims at assessing metalinguistic abilities in Italian-English bilinguals compared to both Italian and English monolinguals. 40 University students (age range: 20-29 y.-old), enrolled in humanistic studies, of middle class background, were recruited partly in Italy and partly in UK. They were all administered a subtest of a metalinguistic ability test devised for adults, the subtest Comprehension, existing in Italian and in English version. Results showed significant metalinguistic superiority of bilinguals over monolinguals in the most complex, type of responsesm although English monolinguals outperformed Italian monolinguals. No differences appeared between simultaneous and consecutive bilinguals

A COMPARATIVE STUDY ON THE FEEDING COMPETITION OF THE EUROPEAN PERCH PERCA FLUVIATILIS L. AND THE RUFFE GYMNOCEPHALUS CERNUUS (L.) IN LAKE PIEDILUCO (UMBRIA, ITALY).

The abundance of European perch in Lake Piediluco has significantly dwindled in the last few years. The present study on diet overlap between perch and ruffe was prompted by the rapid expansion of the ruffe stock in the lake. This species was first found in the lake in 1996 and has since become one of the most abundant. The degree of diet overlap between the two species was analyzed by using data on the stomach contents of 275 European perch and 328 ruffe. Results are expressed as abundance (%N), occurrence (%S), weight percentage (%W) and index of predominance (Ip). The diet overlap index (α) was calculated by means of Schoener’s formula using the %W of each food item. As an estimate of the diet width of both species, we used Levins’ indexes of niche breadth (B) and standardized measurement of niche breadth (BA). Both species are strictly carnivorous, feeding mainly on invertebrates: the most important diet components were dipterans and crustaceans, but the European perch also feeds on fish. In the perch, the Levins index was greater (B=4.332) than that calculated for the ruffe (B=2.262). During the ontogenesis of the European perch, there is a rather pronounced diet shift: dipterans form the largest portion of the diet at all ages, though in older perch fish-eating becomes increasingly evident. Benthic crustaceans tend to be consumed in greater quantities by the 3+ age-class, though they are also found in the stomachs of specimens of all ages. Ruffe, by contrast, do not display a pronounced ontogenetic diet shift. The index of diet overlap between the two species was rather high, the maximum α value being 0.853; values indicate a high degree of diet overlap in the younger ageclasses (1+, 2+ and 3+), with a greater differentiation between the diets of the two species emerging as the age of the perch increased. Our research also clarified some of the biological characteristics of the European perch in Lake Piediluco, namely, theoretical growth in length, weight at length and relative weight. These analyses enabled us to compare the growth characteristics of the European perch during periods when ruffe stocks differed in terms of abundance. All of the results indicate that the growth conditions of the European perch population in Lake Piediluco are steadily worsening. This provides indirect confirmation of a negative interaction with the ruffe

Anisotropic light scattering in water-alcohol mixtures

We have studied the depolarized Rayleigh-Wing light scattering of aqueous solutions of 2-butoxyethanol (C4E1) as a function of the temperature and concentration. The measured spectra give information on the rotational dynamics of water molecules. Their analysis confirm the amphiphilic character of the ethoxylated alcohol molecules that originates micellar structures. In addition, the water dynamics shows, in agreement with récent small angle neutron scattering measurements, the simultaneous presence of micelles and concentration fluctuations. This latters are dominant at high temperatures when one approaches the demixtion curve