TiO(2) nanorods/PMMA copolymer-based nanocomposites: highly homogeneous linear and nonlinear optical material

Original nanocomposites have been obtained by direct incorporation of pre-synthesized oleic acid capped TiO(2) nanorods into properly functionalized poly(methyl methacrylate) copolymers, carrying carboxylic acid groups on the repeating polymer unit. The presence of carboxylic groups on the alkyl chain of the host functionalized copolymer allows an highly homogeneous dispersion of the nanorods in the organic matrix. The prepared TiO(2)/PMMA-co-MA nanocomposites show high optical transparency in the visible region, even at high TiO(2) nanorod content, and tunable linear refractive index depending on the nanoparticle concentration. Finally measurements of nonlinear optical properties of TiO(2) polymer nanocomposites demonstrate a negligible two-photon absorption and a negative value of nonlinear refractive index, highlighting the potential of the nanocomposite for efficient optical devices operating in the visible region.     

The onset of CML in blastic crisis: molecular features

The cytokine tumor necrosis factor alpha (TNF alpha) was proposed to mediate obesity related insulin resistance upon production in fat cells and to participate in tissue remodelling leading to vascular complications upon being released by macrophages. To assess its putative role in diabetes we determined plasma levels of TNF alpha in 105 adult humans. Male nondiabetic subjects had significantly lower TNF alpha levels than female controls (4.4 +/- 0.3, n = 17 vs. 6.6 +/- 1.0 pg/ml, n = 13; p = 0.049). Men with NIDDM had elevated TNF alpha (6.7 +/- 0.6 pg/ml, n = 34) compared to nondiabetic subjects (4.4 +/- 0.3 pg/ml, n = 17; p = 0.012). Such a difference was not apparent in women. Levels of TNF alpha were correlated with serum triglyceride levels in male controls (r2 = 0.64; p = 0.007) but not in NIDDM. Neither body mass index nor glycosylated hemoglobin correlated with TNF alpha in any of the groups. The presence of retinopathy (p = 0.046) but not of neuropathy or nephropathy or macroangiopathy was associated with significantly elevated plasma TNF alpha. We conclude that plasma levels of TNF alpha are sex-dependent and that increased TNF alpha occurs in male but not female NIDDM and may participate in the development of diabetic complications.     

A remote scanning Raman spectrometer for in situ measurements of works of art

In conservation science, one of the main concerns is to extract information from an artistic surface without damaging it. Raman spectroscopy has emerged in recent years as a reliable tool for the non-destructive analysis of a wide range of inorganic and organic materials in works of art and archaeological objects. Nevertheless, the technique is still mainly limited to the analysis of micro-samples taken from artistic surfaces. The development of an instrument able to perform non-contact analysis of an area of a few square centimeters aims to further increase the employment of this technique. This paper describes the development of a prototype Raman scanning spectrometer based on a diode laser, a 2D scanning mirror stage and a custom optical system, which can map a surface of 6 cm in diameter at a working distance of 20 cm. The device exhibits collecting optics with a depth of field close to 6 cm, which makes the Raman system suitable for the analysis of non-flat surfaces and three-dimensional objects. In addition, the overall dimensions and weight of the instrument have been limited in order to make the device transportable and, in principle, usable for in situ measurements. Details on the design of the device, with particular emphasis on the collecting optical system, and on results of the characterization tests carried out to assess its performances are reported. Finally, an example of an application involving the identification of pigments from a model painting is presented.     

Polymer-derived silicon nitride aerogels as shape stabilizers for low and high-temperature thermal energy storage

This work presents a new skeleton material for thermal energy storage (TES), a silicon nitride aerogel obtained through the pyrolysis of a pre-ceramic polymer. Silicon nitride offers a good combination of thermal conductivity, high-temperature resistance, and chemical inertness. The aerogel porosity can be spontaneously infiltrated with molten NaNO₃, which is a typical phase change material (PCM) in high-temperature TES. The Si₃N₄/NaNO₃ composite exhibits excellent thermal properties with a thermal energy storage efficiency of 82 %, a limited molten salt leakage, and good stability to thermal cycling. The aerogel withstands oxidation up to high temperature and is chemically inert even in contact with salts. This novel aerogel shows also a notable paraffin absorption ability (used in room temperature TES) with negligible leakage even when in contact with absorbent paper. The so-obtained composite reached ≈ 82.4 vol % of organic PCM and a thermal energy storage efficiency of ≈ 62 % compared to neat paraffin.     

Low-temperature thermal energy storage with polymer-derived ceramic aerogels

Thermal energy storage (TES) with phase change materials (PCMs) presents some advantages when shape-stabilization is performed with ceramic aerogels. These low-density and ultra-porous materials guarantee high energy density and can be easily regenerated through simple pyrolysis while accounting for moderate mechanical properties. However, the small pore size that typically characterizes these sorbents can hinder the crystallization of PCMs, slightly reducing the energy density of the stabilized compound. In this work, we present the use of polymer-derived mesoporous SiC and SiOC aerogels for the stabilization of polyethylene glycol and a fatty alcohol (PureTemp 23), having a melting temperature of 17 and 23°C, respectively. Their TES performances point out maximum thermal efficiency values of around 80%. These performances are discussed accounting for the results of thermogravimetric analysis, differential scanning calorimetry, and leaking tests.     

Composition of interfacial layers in complex food emulsions before and after aeration: effect of egg to milk protein ratio

Whipped emulsions were prepared at pilot scale from fresh milk, whole egg, and other ingredients, for example, sugars and stabilizers (starch, polysaccharides). Egg content was varied: 4 recipes were studied differing in their egg to milk protein ratio (0, 0.25, 0.38, and 0.68). Protein and fat contents were kept constant by adjusting the recipes with skim-milk powder and fresh cream. Emulsions were prepared by high-pressure homogenization and whipped on a pilot plant. Particle-size distribution determined by laser-light scattering showed an extensive aggregation of fat globules in both mix and whipped emulsions, regardless of recipe. Amount of protein adsorbed at the oil-water interface and protein composition of adsorbed layer were determined after isolation of fat globules. Protein load is strongly increased by the presence of egg in formula. Values obtained for the whipped emulsions were dramatically lower than those obtained for the mix by a factor of 2 to 3. Sodium dodecyl sulfate-PAGE indicated a preferential adsorption of egg proteins over milk proteins at the oil-water interface, regardless of recipe. This phenomenon was more marked in aerated than in unaerated emulsions, showing evidence for desorption of some milk proteins during whipping. Egg proteins stabilize mainly the fat globule surface and ensure emulsion stability before whipping. Air bubble size distribution in whipped emulsions was measured after 15 d storage. When the egg to milk protein ratio is decreased to 0.25, large air cells appear in whipped emulsions during storage, indicating mousse destabilization. The present work allows linking the protein composition of adsorbed layers at the fat globule surface to mousse formula and mousse stability.     

Postharvest structural changes of Hayward kiwifruit by means of magnetic resonance imaging spectroscopy

In the present study magnetic resonance imaging (MRI) was used to evaluate the effect of storage conditions, 0 °C and 90% relative humidity (RH) or 20 °C and 70% RH, on minimal structural changes of kiwi tissue. Storage time was 35 days at 20 °C and 65 days at 0 °C including shelf life. Ethylene and respiration were followed during the experiment as well as commercial quality parameters such as sugars and firmness. MRI images weighted for proton density (ρ) and transverse relaxation times (T₂), were recorded after 10, 20, 35, 55 and 65 days. A decrease of the diameter was clearly visible in samples stored at 20 °C after 3 weeks and a coarse contour of the pericarp appeared after 40 days. Accumulation of water in the pericarp was found, suggesting a migration towards the outer regions occurs and that the fruit water loss due to evapo-transpiration is slower than the migration process. Samples stored at 0 °C showed no relevant changes in dimension and structural features for the whole period considered except after removal to shelf life. The observed variations of the internal morphology were correlated with the transverse relaxation times of defined areas and with softening of fruits. Measured T₂ profiles showed double-exponential decays, a fast- and a slow-relaxing component, indicating the existence of two different types of water molecules within cellular tissues: strongly and weakly bound, respectively. The relation among MRI data, ethylene and softening is discussed.     

Identification of cherry tomatoes growth origin by means of magnetic resonance imaging

Magnetic resonance imaging (MRI) spectroscopy is a promising non‐invasive and non‐destructive analytical technique in food science, since it offers the opportunity of studying vegetables and fruits in their wholeness without any manipulation. The aim of this preliminary study was to demonstrate the possibility of assessing unambiguously the place of origin of fresh cherry tomatoes by means of MRI experiments. The innovative approach has been successfully used to distinguish PGI (Protected Geographical Indication) cherry tomatoes from non‐PGI ones, as well as cv. Naomi from cv. Shiren samples. The method determines informative physical and morphological parameters, transverse relaxation times and thicknesses, respectively, which can be combined into four empirical equations; two of them are used to determine the cultivated variety and the other two to assess the place of origin. This approach has successfully recognize the cultivated variety of c. 90% of the analyzed samples and the geographical origin of c. 80% of the investigated cherry tomatoes. Copyright © 2006 Society of Chemical Industry     

p53 expression in B-cell chronic lymphocytic leukemia: a marker of disease progression and poor prognosis

We have analyzed by immunocytochemistry (ICC) the frequency of p53 protein expression in 181 cases of B-cell chronic lymphocytic leukemia (CLL) followed at a single institution to assess the relationship between p53 and the clinical and morphological features of the disease, as well as the possible involvement of this protein in the pathogenesis of the more aggressive forms of CLL. The overall frequency of p53 protein positivity in CLL was 15% (27 of 181 cases). There were no significant differences in age, sex, absolute lymphocyte count, or lymphocyte doubling time between p53-positive and -negative patients. By contrast, p53-positive patients had a significantly higher percentage of prolymphocytes (P = .002) and a significantly lower percentage of residual CD3-positive T lymphocytes (P = .0001). No correlation was found between the percentage of p53-positive cells and the percentage of cells in cycle assessed by the monoclonal antibody Ki-67. When the percentage of p53 positivity was correlated with the clinical stage of the disease, the proportion of p53-positive cases increased significantly from Binet's stage A (8 of 108; 7.4%), to stage B (12 of 49; 24.4%) and C (7 of 24; 29.2%) (P = .002). p53 positivity correlated also with the phase of the disease, showing a low expression at diagnosis (8 of 112; 7.1%) and a significantly higher expression in patients studied during the course of the disease (7 of 35; 20%) and, to a further extent, with disease progression (12 of 34; 35.3%) (P = .0001). The association of p53 protein expression with mutations in the gene was confirmed by direct sequence of the entire cDNA in 15 of the 17 ICC positive cases tested (88%). A significantly shorter treatment-free interval from diagnosis (P = .003) and a poorer response to therapy (P = .007) was observed in p53-positive compared with p53-negative patients. Overall survival from the time of diagnosis, as well as from the time of p53 protein analysis, was significantly shorter in patients with p53 protein expression (P = .03 and .0001, respectively). Moreover, in multivariate analysis, p53 expression and stage C were independently associated with a short survival. The results of this study indicate that in CLL the expression of the p53 protein, analyzed by a simple and reliable immunocytochemical method, is strongly associated with p53 gene mutations, a morphological variant (CLL with >10% prolymphocytes), advanced clinical stage, progressive disease, poor response to therapy, and short survival.