Physical properties of 2-hydroxyethyl methacrylate-grafted silk fibers

This paper deals with the physical properties of silk fibers grafted with 2-hydroxyethyl methacrylate (HEMA). Both tensile strength and elongation measured in the dry and wet states gradually decreased with increasing weight gain. The initial modulus of the grafted silk fibers in the dry state sharply increased in the weight gain range of 0–16%, then decreased to a lower value than the reference untreated sample. The refractive indices parallel and perpendicular to the fiber axis decreased, though the former showed a steeper slope. Accordingly, birefringence and isotropic refractive index also decreased, suggesting a lower degree of crystallinity and molecular orientation of grafted silk fibers. DSC, TMA, and TGA curves of the HEMA-grafted silk fibers indicated an increased higher thermal stability of silk fibers due to the HEMA grafting. The dynamic mechanical measurements showed that the thermally induced molecular movement of both amorphous and crystalline domains of silk fibers was enhanced by HEMA grafting. X-ray diffraction curves, however, implied that the crystalline structure of the silk fibroin remained unchanged regardless of HEMA polymerization. The introduction of HEMA polymer in silk fibers was evidenced by the infrared spectra, exhibiting the absorption bands characteristic of either the grafted HEMA polymer and the fibroin molecules with ordered β structure. © 1993 John Wiley & Sons, Inc.     

Low-Temperature Synthesis and Properties of LaMnO3±d and La0.67R0.33MnO3±d (R = Ca, Sr, Ba) from Citrate Precursors

LaMn_{1− y} ³⁺Mn _y ⁴⁺O_3±d and La_0.67R_0.33Mn_{1− y} ³⁺Mn _y ⁴⁺O_3±d (R = Ca, Sr, Ba) phases were synthesized at 350°C by using very reactive, amorphous precursors obtained from the stoichiometric citrate solutions. The chemical process was optimized with respect to the solution concentration, pH, and additives. The precursor reactions were investigated as a function of the cation stoichiometry and the additive by simultaneous thermal and thermogravimetric analysis and X-ray diffraction. The reaction pathway was found to be independent of the cation stoichiometry, but related to the acid or base additive. The annealing temperature was systematically increased in the 350–1200°C interval and the La_0.67Sr_0.33MnO_3±d properties (i.e., crystal sizes, Mn average valence, Curie temperature, magnetization, magnetic susceptibility) were measured and found to vary consistently as a function of it.     

X-ray microscopy of plant cells by using LiF crystal as a detector

A lithium fluoride (LiF) crystal has been utilized as a new soft X-ray detector to image different biological samples at a high spatial resolution. This new type of image detector for X-ray microscopy has many interesting properties: high resolution (nanometer scale), permanent storage of images, the ability to clear the image and reuse the LiF crystal, and high contrast with greater dynamic range. Cells of the unicellular green algae Chlamydomonas dysosmos and Chlorella sorokiniana, and pollen grains of Olea europea have been used as biological materials for imaging. The biological samples were imaged on LiF crystals by using the soft X-ray contact microscopy and contact micro-radiography techniques. The laser plasma soft X-ray source was generated using a Nd:YAG/Glass laser focused on a solid target. The X-ray energy range for image acquisition was in the water-window spectral range for single shot contact microscopy of very thin biological samples (single cells) and around 1 keV for multishots microradiography. The main aim of this article is to highlight the possibility of using a LiF crystal as a detector for the biological imaging using soft X-ray radiation and to demonstrate its ability to visualize the microstructure within living cells.     

Three-dimensional image restoration and super-resolution in fluorescence confocal microscopy

Confocal scanning laser microscopy (CSLM) provides optical sectioning of a fluorescent sample and improved resolution with respect to conventional optical microscopy. As a result, three-dimensional (3-D) imaging of biological objects becomes possible. A difficulty is that the lateral resolution is better than the axial resolution and, thus, the microscope provides orientation-dependent images. However, a theoretical investigation of the process of image formation in CSLM shows that it must be possible to improve the resolution obtained in practice. We present two methods for achieving such a result in the case of 3-D fluorescent objects. The first method applies to conventional CSLM, where the image is detected only on the optical axis for any scanning position. Since the resulting 3-D image is the convolution of the object with the impulse-response function of the instrument, the problem of image restoration is a deconvolution problem and is affected by numerical instability. A short introduction to the linear methods developed for obtaining stable solutions of these problems (the so-called regularization theory of ill-posed problems) is given and an application to a real image is discussed. The second method applies to a new version of CSLM proposed in recent years. In such a case the full image must be measured by a suitable array of detectors. For each scanning position the data are not single numbers but vectors. Then, in order to recover the object, one must solve a Fredholm integral equation of the first kind. A method for the solution of this equation is presented and the possibility of achieving super-resolution is demonstrated. More precisely, we show that it is possible to improve by about a factor of 2 the resolution of conventional CSLM both in the lateral and axial directions.     

Cultural Landscape: Stone Towers on Mount Etna

This work reports the findings of an investigation by Etna’s local councils whose publicly owned land has high concentrations of particularly significant towers. The towers are original stone constructions, presumed to have been built between the end of the 1700s and the beginning of the 1900s and so are unrelated to medieval towers, emblems of ancient yet sophisticated building techniques and located in numerous agricultural areas on the slopes of Mount Etna, Europe’s most active volcano. They are built out of the stones removed from the agricultural land of the soils regenerated from the lava flows wedged in between basalt outcrops. Together with other stone artefacts, they form part of a renewable heritage of great value both for their recognised role in maintaining biodiversity as well as for their cultural, landscape and historical significance. These constructions are in a state of extreme abandonment or are gradually disappearing due to the loss of agriculture or the changeover of agricultural land into building sites. The enquiry used historical documents, censuses of tower characteristics and field data. Four council zones were identified and in each only clearly identifiable towers were considered (total: 19). The field data highlighted considerable architectural complexity in their proportions and construction techniques. Their historico-cultural-landscape validity was confirmed as was the necessity of appropriate and urgent state intervention.     

Expression of α-amylase inhibitors in diploid Triticum species

The aim of the work was to characterize the expression of various α-amylase inhibitors (αAIs), well known anti-nutritional compounds, for the development of healthier diploid wheat-based functional foods.     

Value of maturity models in performance measurement

Over the last 20 years, the field of performance measurement (PM) has evolved from measurement to management. Investigations demonstrated the relevance of PM in management of organisations’ results. Although maturity model concept was widely used, the value of maturity models in PM has not been purposefully investigated. To address this gap, this research formulated three research questions: (1) How do maturity models in the field of performance measurement and management (PM&;M) add value in practice? (2) How do such maturity models compliment and/or replicate the value added by an expert? (3) How do maturity models contribute to the development of the organisation’s PM&;M practices? Using a predefined research protocol, 12 European manufacturing organisations and independent experts were engaged in conducting two separate studies: (1) the experts conducted reviews with 12 companies using a standard business review format; (2) research team adopted one of the available maturity models and facilitated self-assessments with the management teams of the same 12 companies. Results from both the studies were compared and high levels of congruence were identified. The analysis demonstrates that the maturity models with certain characteristics, promote organisational learning as well as enabling efficient and effective assessment of the performance management practices of the organisations.     

Simultaneous determination of anthocyanins,coumarins and phenolic acids in fruits,kernels and liqueur of Prunus mahaleb L

In the fresh tissues of Prunus mahaleb L., three classes of phenolics were characterised: phenolic acid derivatives (main compound being o-coumaric acid glucoside), quercetin glycosides, and anthocyanins (cyanidin 3,5-diglucoside, cyanidin 3-sambubioside, cyanidin 3-xylosyl-rutinoside and cyanidin 3-rutinoside). Coumarin was also identified. The kernels showed a high content of coumarin (0.87 mg g^?1) which is the main class of metabolites in this sample, but present in pitted berries as well (0.63 mg g^?1). Flavonoids are mainly concentrated in the skin and pulp (0.55 mg g^?1). In ‘Mirinello di Torremaggiore’ liqueur, produced from P. mahaleb L. in accordance with traditional procedures, anthocyanins make up 16.5%, phenolic acids 43.3%, coumarin 36.2% and flavonoids 4% of total compounds. Anthocyanins are the main class in solid residues from liqueur production (70%). These findings point out that solid residues of P. mahaleb can be considered an interesting and innovative source of appreciable amounts of cyanidin glycosides (3.3 mg g^?1).     

Exploring the Role of Genetic Variability and Lifestyle in Oxidative Stress Response for Healthy Aging and Longevity

Oxidative stress is both the cause and consequence of impaired functional homeostasis characterizing human aging. The worsening efficiency of stress response with age represents a health risk and leads to the onset and accrual of major age-related diseases. In contrast, centenarians seem to have evolved conservative stress response mechanisms, probably derived from a combination of a diet rich in natural antioxidants, an active lifestyle and a favorable genetic background, particularly rich in genetic variants able to counteract the stress overload at the level of both nuclear and mitochondrial DNA. The integration of these factors could allow centenarians to maintain moderate levels of free radicals that exert beneficial signaling and modulator effects on cellular metabolism. Considering the hot debate on the efficacy of antioxidant supplementation in promoting healthy aging, in this review we gathered the existing information regarding genetic variability and lifestyle factors which potentially modulate the stress response at old age. Evidence reported here suggests that the integration of lifestyle factors (moderate physical activity and healthy nutrition) and genetic background could shift the balance in favor of the antioxidant cellular machinery by activating appropriate defense mechanisms in response to exceeding external and internal stress levels, and thus possibly achieving the prospect of living a longer life.