Lipid domain pixelation patterns imposed by e-beam fabricated substrates

This work describes a technique for forming nanometer-scale pixilated lipid domains that are self-organized into geometric patterns residing on a square lattice. In this process, a lipid multibilayer stack is deposited onto a silica substrate patterned with a square lattice array of bumps, hemispherical on their sides, formed by electron beam lithography. Domain patterns are shown to be confined to the flat grid between the bumps and composed of connected and individual domain pixels. Analysis of lattices of varying sizes shows that domain pattern formation is driven by mechanical energy minimization and packing constraints. We demonstrate single lattice sizes and a gradient in lattice size varying from the micrometer to the 100 nm scale applicable to precise arraying, patterning, and transport of biomolecules that partition to lipid domains.     

Study of Late Roman and Byzantine glass by the combined use of analytical techniques

In the present work, we report on a detailed characterization of Late Roman and Byzantine (from 2nd to 8th century A.D.) glass specimen found in Catania (Sicily, Southern Italy) by the employment of two complementary techniques, namely scanning electron microscopy coupled with energy-dispersive spectrometry (SEM–EDS) and Fourier transform infrared (FT-IR) absorbance spectroscopy. The glass fragments come from archaeological excavations in the courtyard of St. Agata la Vetere's church in Catania. In particular, compositional data were obtained by scanning SEM–EDS measurements and the investigation of the degradation on the surface of the glass specimen was made combining the SEM–EDS observations with those performed through FT-IR absorbance. The whole set of results contributed to define the provenance of the specimens. Furthermore, the data furnished new evidences of the technical development of glass production in Late Roman and Byzantine period in Catania.     

Structural and dielectric properties of polyvinyl alcohol/barium zirconium titanate polymer–ceramic composite

The polyvinyl alcohol (PVA)/barium zirconium titanate Ba[Zr_0.1Ti_0.9]O₃ (BZT) polymer–ceramic composites with different volume percentage are obtained from solution mixing and hot-pressing method. Their structural and electrical properties are characterized by X-ray diffraction (XRD), Rietveld refinement, cluster modeling, scanning electron microscope and dielectric study. XRD patterns of PVA/BZT polymer–ceramics composite (with 50% volume fractions) indicate no obvious differences than the XRD patterns of pure BZT which shows that the crystal structure is still stable in the composite. The scanning electron micrograph indicates that the BZT ceramic is dispersed homogeneously in the polymer matrix without agglomeration. The dielectric permittivity (ε_r) and the dielectric loss (tan δ) of the composites increase with the increase of the volume fraction of BZT ceramic. Theoretical models are employed to rationalize the dielectric behavior of the polymer composites. The dielectric properties of the composites display good stability within a wide range of temperature and frequency. The excellent dielectric properties of these polymer–ceramic composites indicate that the BZT/PVA composites can be a candidate for embedded capacitors.     

Long-term stability by lipid coating monodisperse microbubbles formed by a flow-focusing device

In this letter, the long-term stabilization of monodisperse microbubbles produced by flow focusing is demonstrated using lipid encapsulation. Fluorescence microscopy, high-speed camera imaging, and particle size analysis were used to investigate the roles of lipid phase behavior, dissolution, Ostwald ripening, and coalescence in the stability of microbubbles formed by flow focusing. It was found that these behaviors were controlled through compositional changes with respect to lipid, emulsifier, and viscosity agents. Microbubbles coated with lipid and PEG emulsifier in a viscous solution were found to contain an extremely narrow size distribution (diameter(av) = 51 microm, standard deviation = 4 microm), which was maintained for up to several months.     

Collapse and shedding transitions in binary lipid monolayers coating microbubbles

We report on a fluorescence microscopy study of the monolayer collapse and shedding behavior due to shell compression during the dissolution of air-filled, lipid-coated microbubbles in degassed media. The monolayer shell was comprised of saturated diacyl phosphatidylcholine (C12:0 to C22:0) and an emulsifier, poly(ethylene glycol)-40 stearate. The morphologies of monolayer collapse structures and shed particles were monitored as a function of phospholipid acyl chain length (n) and temperature. The two components formed a single miscible phase when the phospholipid was near or above its main phase transition temperature, and collapse occurred via suboptical particles to vesicles (both were shed) and tubes as chain length increased. Conversely, two-phase coexistence was observed when the lipid was below its main phase transition temperature. For these bubbles, a transition from primary collapse to secondary collapse was observed. Primary collapse was observed as a loss of expanded phase due to vesiculation. Secondary collapse involved the rapid propagation of monolayer folds and simultaneous deformation. For very rigid monolayers, we observed substantial surface buckling with simultaneous nucleation and growth of folds. The folds merged at a single point or region, providing a conduit for the entire excess lipid to shed in a single event, and the bubble smoothed and became more spherical. These results are discussed in the context of general binary phospholipid collapse behavior, microbubble dissolution behavior, medical applications, and the dissolution behavior of natural microbubbles.     

Growth of SnO nanobelts and dendrites by a self-catalytic VLS process

This article reports on the growth of SnO nanobelts and dendrites by a carbothermal reduction process. The materials were synthesized in a sealed tube furnace at 1210 degrees C and at 1260 degrees C for 2 h, in a dynamic nitrogen atmosphere of 40 sccm. After synthesis, gray-black materials were collected downstream in the tube and the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The results showed that the gray-black materials were composed of nanobelts, which grew in the [110] direction of the orthorhombic structure of SnO. Some of the belts also presented dendritic growth. The dendrites grew in the (110) planes of the SnO structure, and no defects were observed at the junction between the nanobelts and the dendrites. A self-catalytic vapor-liquid-solid (VLS) process was proposed to explain the growth of the SnO nanobelts and dendrites.     

Thermal States in Conformal QFT. I

We analyze the set of locally normal KMS states w.r.t. the translation group for a local conformal net A{{\mathcal A}} of von Neumann algebras on \mathbb R{\mathbb R} . In this first part, we focus on the completely rational net A{{\mathcal A}} . Our main result here states that, if A{{\mathcal{A}}} is completely rational, there exists exactly one locally normal KMS state j{\varphi} . Moreover, j{\varphi} is canonically constructed by a geometric procedure. A crucial r?le is played by the analysis of the “thermal completion net” associated with a locally normal KMS state. A similar uniqueness result holds for KMS states of two-dimensional local conformal nets w.r.t. the time-translation one-parameter group.     

SnO<Subscript>2</Subscript> nanocrystals synthesized by microwave-assisted hydrothermal method: towards a relationship between structural and optical properties

The exploration of novel synthetic methodologies that control both size and shape of functional nanostructure opens new avenues for the functional application of nanomaterials. Here, we report a new and versatile approach to synthesize SnO₂ nanocrystals (rutile-type structure) using microwave-assisted hydrothermal method. Broad peaks in the X-ray diffraction spectra indicate the nanosized nature of the samples which were indexed as a pure cassiterite tetragonal phase. Chemically and physically adsorbed water was estimated by TGA data and FT-Raman spectra to account for a new broad peak around 560 cm⁻¹ which is related to defective surface modes. In addition, the spherical-like morphology and low dispersed distribution size around 3–5 nm were investigated by HR-TEM and FE-SEM microscopies. Room temperature PL emission presents two broad bands at 438 and 764 nm, indicating the existence of different recombination centers. When the size of the nanospheres decreases, the relative intensity of 513 nm emission increases and the 393 nm one decreases. UV–Visible spectra show substantial changes in the optical absorbance of crystalline SnO₂ nanoparticles while the existence of a small tail points out the presence of localized levels inside the forbidden band gap and supplies the necessary condition for the PL emission.     

Iron speciation in ancient Attic pottery pigments: a non‐destructive SR‐XAS investigation

The present work reports a detailed investigation on the speciation of iron in the pigments of decorated pottery fragments of cultural heritage relevance. The fragments come from the Gioiosa Guardia archaeological site in the area of the `Strait of Messina' (Sicily, Southern Italy), and date back to VI–V century BC. The purpose of this study is to characterize the main pigmenting agents responsible for the dark‐red coloration of the specimens using non‐destructive analytical techniques such as synchrotron radiation X‐ray absorption spectroscopy (SR‐XAS), a well established technique for cultural heritage and environmental subjects. Absorption spectra were collected at the Fe K‐edge on the Italian beamline for absorption and diffraction (BM8‐GILDA) at the European Synchrotron Radiation Facility in Grenoble (France). In order to determine the speciation of Fe in the samples, principal component analysis and least‐squares fitting procedures were applied to the near‐edge part of the absorption spectra (XANES). Details on the local structure around the Fe sites were obtained by analyzing the extended part of the spectra (EXAFS). Furthermore, an accurate determination of the average Fe oxidation state was carried out through analysis of the pre‐edge peaks of the absorption spectra. Samples resulted composed of an admixture of Fe₂O₃ (hematite or maghemite) and magnetite (Fe₃O₄), occurring in different relative abundance in the dark‐ and light‐colored areas of the specimens. The results obtained are complementary to information previously obtained by means of instrumental neutron activation analysis, Fourier transform infrared absorbance and time‐of‐flight neutron diffraction.     

“4,7-lactams”, intermediates for penems synthesis. II. Total synthesis of (+)-2,2-dimethyl-9-oxo-3-oxa-6-thia-1-azabicyclo [5.2.01,7]nonane

The total synthesis of chiral “4,7-lactam” $\text{4}$ has been accomplished starting from 4-acetoxyazetidinone. An independent route from methyl penicillanate has been used to test the efficiency of the foregoing synthesis.