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991.
The concentrations of protein, fat, five minerals (Na, K, P, Ca and Mg) and nine trace elements (Fe, Zn, Cu, Mn, Se, Al, Cd, Cr and Pb) have been determined in 347 samples of raw cow milk from the community of Navarra, north Spain, using infrared analysis, atomic absorption spectrometry (flame and electrothermal atomisation) and inductively coupled plasma atomic emission spectroscopy. A preliminary chemometric study with the use of pattern recognition methods was carried out in order to characterise, classify and distinguish the different collected samples on the basis of their contents. Principal component analysis (PCA) has permitted the reduction of 16 variables to five principal components which interpret reasonably well the correlations of these studied variables. These variable associations may be attributed to intrinsic (lactogenesis) and other extrinsic factors, such as seasonal variation, animal feeding or geographical situation. Changes in these contents during different seasons were also assessed and consistently interpreted. Linear discriminant analysis (LDA) was used to explore cow milk samples, classifying according to season or geographical location, providing complementary information to PCA. This work shows that PCA and LDA are useful chemometric tools for the multivariate characterisation of raw cows’ milk. 相似文献
992.
The spore-forming genus Bacillus includes species of industrial, clinical and environmental significance. The possibility of differentiating between Bacillus cereus and Bacillus thuringiensis, toxin producers associated with illness, is a real need in monitoring potentially contaminated foods to understand the real distribution of B. cereus/B. thuringiensis in different outbreak cases. As the use of DNA comparison obtains clearer results than classical microbiological methods in distinguishing B. cereus from B. thuringiensis in this work PCR-TTGE (Temporal Temperature Gradient gel Electrophoresis), rep-PCR and RAPD-PCR methods have been compared to assess the intra- and inter-specific variability of B. cereus and B. thuringiensis. 80 strains of B. cereus and B. thuringiensis isolated from food, patients and pesticides were analyzed using a gyrB gene DNA sequence in TTGE; primer M13 in the RAPD-PCR and primers REP1DT and REP2DT in the rep-PCR methods. A widespread distribution of the electrophoretic profiles was obtained either for B. cereus or for B. thuringiensis using TTGE. rep-PCR and RAPD-PCR were not always able to group strains from the same origin or belonging to the same species. The fingerprints obtained with the rep- and RAPD-PCR methods confirm the high intraspecific variability present in B. cereus and B. thuringiensis indicating the difficulty to discriminate between these two species in outbreak cases. 相似文献
993.
Andréia Assunção Soares Cristina Giatti Marques de Souza Francielle Marina Daniel Gisele Pezente Ferrari Sandra Maria Gomes da Costa Rosane Marina Peralta 《Food chemistry》2009
The antioxidant capability and total phenolic contents of methanolic extracts of Agaricusbrasiliensis in two stages of maturity, young (YB) and mature (MB), were evaluated in this work. Four complementary assays, reducing power, radical scavenging capacity, inhibition of lipid peroxidation and chelating ability for ferrous ions were used to screen the antioxidant properties of extracts. Minor differences in the composition of phenolic compounds were detected, but the extracts showed similar antioxidant activities, except for the chelating ability for ferrous ions, higher in MB than in YB. Our results support the use of both young and mature fruiting bodies of Agaricus blazei as sources of antioxidant compounds. 相似文献
994.
Palacios C 《Critical reviews in food science and nutrition》2006,46(8):621-628
Osteoporosis is a major public health problem, affecting millions of individuals. Dietary intake is an important modifiable factor for bone health. Inadequate intake of nutrients important to bone increases the risk for bone loss and subsequent osteoporosis. The process of bone formation requires an adequate and constant supply of nutrients, such as calcium, protein, magnesium, phosphorus, vitamin D, potassium, and fluoride. However, there are several other vitamins and minerals needed for metabolic processes related to bone, including manganese, copper, boron, iron, zinc, vitamin A, vitamin K, vitamin C, and the B vitamins. Although the recommended levels of nutrients traditionally related to bone were aimed to promote bone mass and strength, the recommended levels of the other nutrients that also influence bone were set on different parameters, and may not be optimal for bone health, in view of recent epidemiological studies and clinical trials. 相似文献
995.
A Portland cement process was taken into consideration and monitored for one month with respect to polluting emissions, fuel and raw material physical-chemical properties, and operative conditions. Soft models, based on linear (partial least-squares, PLS, and principal component regression, PCR) and nonlinear (artificial neural networks, ANNs) approaches, were employed to predict the polluting emissions. The predictive ability of the three regression methods was evaluated by means of the partition of the dataset by Kohonen self-associative maps into both a training and a test set. Then, a "leave-more-out" approach, based on the use of a training set, a test set, and a production set, was adopted. The training set was used to build the models, the test set was used to select the number of latent variables or the neural network training endpoint, and the production set was used to produce genuine predictions. ANNs proved to be much more effective in prediction with respect to PLS and PCR and, at least in the case of SO2 and dust, provided a predictive ability comparable with the experimental estimated uncertainty of the response. This showed that it is possible to satisfactorily predict the two responses. Such a prediction will result in the prevention of environmental and legal problems connected to the polluting emissions. 相似文献
996.
Optimal-control methods for two new classes of smart obstacles in time-dependent acoustic scattering
Lorella Fatone Graziella Pacelli Maria Cristina Recchioni Francesco Zirilli 《Journal of Engineering Mathematics》2006,56(4):385-413
Time-dependent acoustic scattering problems involving “smart” obstacles are considered. When hit by an incident acoustic field,
smart obstacles react in an attempt to pursue a preassigned goal. Let
be the three-dimensional real Euclidean space, and let
be a bounded simply connected open set with a Lipschitz boundary characterized by a constant acoustic boundary impedance
χ, immersed in an isotropic and homogeneous medium that fills
. The closure of Ω will be denoted as
. When hit by an incident field, the obstacle Ω pursues the preassigned goal through the action of a control input acting
on its boundary (i.e., a quantity with dimensions of a pressure divided by a time). The obstacles considered in this paper
monitor the control input acting on their boundaries in order to achieve one of the following goals: (i) be furtive in a given
set of the frequency space, and (ii) appear in a given set of the frequency space and outside a given set of
containing Ω and Ω
G
as similar as possible to a “ghost” obstacle Ω
G
having boundary acoustic impedance χ
G
. It is assumed that
and
. The problem corresponding to the first goal will be called the definite-band furtivity problem, and the problem corresponding
to the second goal will be called the definite-band ghost-obstacle problem. These two goals define two classes of smart obstacles.
In this paper, these problems are modeled as optimal-control problems for the wave equation introducing a control input acting
on the boundary of Ω for time
. The cost functionals proposed depend on the value of the control input on the boundary of the obstacle and on the value
of the scattered acoustic field generated by the obstacle on the boundary in the “furtivity case”, and on the boundary of
a suitable set containing Ω and Ω
G
in the “ghost-obstacle case”. Under some assumptions, the use of the Pontryagin maximum principle allows us to formulate
the first-order optimality conditions for the definite-band furtivity problem and for the definite-band ghost-obstacle problem
as exterior problems outside the obstacle for a system of two coupled wave equations. Numerical methods to solve these exterior
problems are developed by extending previous work. These methods belong to the class of the operator-expansion methods that
are highly parallelizable. Numerical experiments proving the validity of the control problems proposed as mathematical models
of the definite-band furtivity problem and definite-band ghost obstacle problem are presented. The numerical results obtained
with a parallel implementation of the numerical methods developed are discussed and their properties are established. The
speed-up factors obtained using parallel computing are really impressive. The website: http://www.econ.univpm.it/recchioni/w11 contains animations and virtual reality applications relative to the numerical experiments. 相似文献
997.
A variety of techniques (secondary electron microscopy with energy dispersive X-ray analysis, time-of-flight--secondary ion mass spectrometry, and synchrotron X-ray fluorescence) were utilized to distinguish metal contamination occurring in hair arising from endogenous uptake from an individual exposed to a polluted environment, in this case a lead smelter. Evidence was sought for elements less affected by contamination and potentially indicative of biogenic activity. The unique combination of surface sensitivity, spatial resolution, and detection limits used here has provided new insight regarding hair analysis. Metals such as Ca, Fe, and Pb appeared to have little representative value of endogenous uptake and were mainly due to contamination. Cu and Zn, however, demonstrate behaviors worthy of further investigation into relating hair concentrations to endogenous function. 相似文献
998.
Summary: In this work, the relationships between the microstructure and the mechanical properties of injection moldings using a special mold for manipulation of their microstructure are studied. Distinct molding microstructures were obtained by superimposing a mold surface rotation action in different rotation modes during the filling stage of a center‐gated disk. For this, disks were injected in the special molding tool—the RCE mold—with distinct filling sequences (stationary, continuous, stepped, and pulsed rotation modes) for two different thicknesses (1.5 and 2.5 mm) in a propylene homopolymer. This enables the development of a wide range of microstructures, which were characterized by polarized light microscopy. The mechanical behavior of the moldings was assessed by tensile and impact testing. The results are presented in terms of the relationships between the developed microstructure and the assessed mechanical properties. The imposition of a rotation action of the molds wall influences the development of the microstructure, and hence the mechanical properties of the moldings.
999.
Prazeres VF Sánchez-Sixto C Castedo L Canales A Cañada FJ Jiménez-Barbero J Lamb H Hawkins AR González-Bello C 《ChemMedChem》2006,1(9):990-996
The synergy between tuberculosis and the AIDS epidemic, along with the surge of multidrug-resistant isolates of M. tuberculosis, has reaffirmed tuberculosis as a primary public health threat. It is therefore necessary to discover new, safe, and more efficient antibiotics against this disease. On the other hand, mapping the dynamic interactions of inhibitors of a target protein can provide information for the development of more potent inhibitors and consequently, more potent potential drugs. In this context, the conformational binding of our previously reported nanomolar inhibitor of M. tuberculosis type II dehydroquinase, the 3-nitrophenyl derivative 1, was studied using saturation transfer difference (STD) and transferred NOESY experiments. These studies have shown that in the bound state, one conformation of those present in solution of the competitive nanomolar inhibitor 3-nitrophenyl derivative 1 is selected. In the bound conformation, the aromatic ring is slightly shifted from coplanarity, with the double bond and the nitro group of 1 oriented towards the double bond side. 相似文献
1000.