Search results for "crystalline"

Commercial essential oils: sustainable alternatives in the agri-food industry

2019

Essential oils have enjoyed great popularity from ancient times to today due to agreeable scent and widely known beneficial properties. As a result, nowadays they have become valuable natural ingredients in perfume and cosmetics, food and beverages, agricultural, pharmaceutical and other industries for employment in human health, agriculture and environment, representing potentially safer and more sustainable alternatives to synthetic substances. This Doctoral Thesis has been developed with the aim of corroborating that essential oils are safer and more sustainable alternatives to synthetic products used in the agri-food industry, and consequently promoting their use as “bio” products to ma…

Growth of large liquid crystalline domains of phospholipids at air-water interfaces

1990

Abstract The fusion of condensed phase domains in a fluid environment in monolayers is studied. A system of electrodes permits the non-invasive and predetermined movement of single domains while the film is observed by fluorescence microscopy. Two domains fuse when they are brought into contact with special positions of their borderlines. The experiment yields information about the molecular structure of the domains and allows us to fabricate very large domains. The equilibrium size is estimated and verified.

Polymers with Side-chain Mesogenic Units

1989

Liquid crystalline (LC) polymers are usually prepared by combining formanisotropic structural units (so-called mesogenic groups) and polymer chains (Figure 1). The mesogenic groups used for this purpose are rigid rod-like or disc-like units, which are known to favour LC phases in the case of low molar mass substances. There are two main ways of combining the mesogenic groups and polymer chains. The mesogenic groups can either be incorporated actually into the polymer chains (LC main-chain polymers, see Volume 5, Chapter 38) or they can be attached to flexible polymer chains as side groups (LC side-chain polymers).

Glass Transition and Food Technology: A Critical Appraisal

2002

ABSTRACT: Most low water content or frozen food products are partly or fully amorphous. This review will discuss the extent to which it is possible to understand and predict their behavior during processing and storage, on the basis of glass transition temperature values (Tg) and phenomena related to glass transition. Two main conclusions are provisionally proposed. Firstly, glass transition cannot be considered as an absolute threshold for molecular mobility. Transport of water and other small molecules takes place even in the glassy state at a significant rate, resulting in effective exchange of water in multi-domains foods or sensitivity to oxidation of encapsulated materials. Texture pr…

Preparation and photoactivity of nanocrystalline TiO2 powders obtained by thermohydrolysis of TiOSO4

2013

Nanocrystalline TiO2 photocatalysts were synthesized in mild conditions by thermohydrolysis of TiOSO4 in water at 100 °C and post-calcination treatment at various temperatures. The TiO2 powders were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, specific surface area determinations, scanning electron microscopy and electron paramagnetic resonance measurements. The photoactivity of the samples was tested employing the photodegradation of 4-nitrophenol in liquid–solid regimen and the photooxidation of gaseous 2-propanol. The best results were obtained with the powder calcined at 600 °C for 10 h. Surprisingly, the not calcined sample was the most active for the abatement…

Lens-vault analysis and its correlation with other biometric parameters using swept-source OCT

2021

Purpose To measure lens vault (LV) and to assess its correlation with various ocular parameters in healthy eyes, using for all measurements the same high-resolution swept-source optical coherence tomographer (SS-OCT). Methods We prospectively recruited 67 Caucasian healthy patients whose mean age was 41.9 ± 12.4 years; only their right eye was included in the study. Data were all recorded with the ANTERION SS-OCT and comprised, for each patient, 5 consecutive measurements of LV, anterior chamber depth (ACD), lens thickness (LT), axial length (AL), white-to-white (WTW) distance, central corneal thickness (CCT), anterior chamber volume (ACV) and spur-to-spur (STS) distance. Results Mean LV wa…

1985

Etude des phases isotrope, nematique et smectique de melanges de polymeres protones et en partie deuteries

Comparing the luminescence processes of YVO4:Eu and core-shell YVO4@YF3 nanocrystals with bulk-YVO4:Eu

2017

Abstract Comparative analysis of bulk, non-coated and core-shelled nanocrystalline YVO4:Eu was performed by means of time-resolved luminescence and VUV excitation luminescence spectroscopy techniques. Nanocrystalline YVO4:Eu samples – both as-prepared and YF3 core-shelled – have been synthesized by means of a microwave-assisted synthesis in ionic liquids, which allows to obtain 10–12 nm nanoparticles with high crystallinity. The results show noticeable differences between bulk and nanocrystalline YVO4:Eu in photoluminescence experimental data, which explains by influence of the nanocrystal surface. A YF3 core-shell layer around YVO4:Eu nanoparticles partially recovers the intensity of the E…

Compressibility and structural behavior of pure and Fe-doped SnO2 nanocrystals

2017

We have performed high-pressure synchrotron X-ray diffraction experiments on nanoparticles of pure tin dioxide (particle size ~30nm) and 10 mol % Fe-doped tin dioxide (particle size ~18nm). The structural behavior of undoped tin dioxide nanoparticles has been studied up to 32 GPa, while the Fe-doped tin dioxide nanoparticles have been studied only up to 19 GPa. We have found that both samples present at ~13 GPa a second-order structural phase transition from the ambient pressure tetragonal rutile-type structure (P42/mnm) to an orthorhombic CaCl2-type structure (space group Pnnm). No phase coexistence was observed for this transition. Additionally, pure SnO2 presents a phase transition to a …

Confinement inside a Crystalline Sponge Induces Pyrrole To Form N−H⋅⋅⋅π Bonded Tetramers

2021

Based on the DFT‐level calculated molecular volume (V mol ) of pyrrole and its liquid density, pyrrole manifests the highest liquid density coefficient LD c (defined as [V mol • density • 0.6023]/FW) value of 0.7. Normal liquids have LD c < 0.63. This very high LD c is due to the strong N‐H … π interactions in solution and hence pyrrole can be considered to be a pseudo‐crystalline liquid. When trapped inside the confined space of the crystalline sponge a reorientation of the N‐H … π interaction is observed leading to specific cyclic N‐H … π tetramers and N‐H … π dimers, verified by single crystal X‐ray crystallographic and computational methods. These tetramers are of the same size as four …