5,662 research outputs found

    The interaction-strength interpolation method for main-group chemistry: benchmarking, limitations, and perspectives

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    We have tested the original interaction-strength-interpolation (ISI) exchange-correlation functional for main group chemistry. The ISI functional is based on an interpolation between the weak and strong coupling limits and includes exact-exchange as well as the G\"orling-Levy second-order energy. We have analyzed in detail the basis-set dependence of the ISI functional, its dependence on the ground-state orbitals, and the influence of the size-consistency problem. We show and explain some of the expected limitations of the ISI functional (i.e. for atomization energies), but also unexpected results, such as the good performance for the interaction energy of dispersion-bonded complexes when the ISI correlation is used as a correction to Hartree-Fock.Comment: 20 pages, 20 figure

    Left main bronchus compression due to main pulmonary artery dilatation in pulmonary hypertension: two case reports

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    Abstract. Pulmonary arterial dilatation associated with pulmonary hypertension may result in significant compression of local structures. Left main coronary artery and left recurrent laryngeal nerve compression have been described. Tracheobronchial compression from pulmonary arterial dilatation is rare in adults, and there are no reports in the literature of its occurrence in idiopathic pulmonary arterial hypertension. Compression in infants with congenital heart disease has been well described. We report 2 cases of tracheobronchial compression: first, an adult patient with idiopathic pulmonary arterial hypertension who presents with symptomatic left main bronchus compression, and second, an adult patient with Eisenmenger ventricular septal defect and right-sided aortic arch, with progressive intermedius and right middle lobe bronchi compression in association with enlarged pulmonary arteries

    Nanostructured ZrO₂ ceramic PVD coatings on Nd-Fe-B permanent magnets

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    The results of vacuum-arc deposition (PVD) of thin ZrO2 coatings to protect the surface of Nd-Fe-B permanent magnets used as repelling devices in orthodontics are presented. Magnetic devices are offered as an optimum and biologically safe forcegenerating system for orthodontic tooth movement. The structure, phase composition and mechanical properties of zirconium oxide films have been investigated by means of SEM, XRD, EDX, XRF and nanoindentation methods. The coatings are formed of polycrystalline ZrO2 films of monoclinic modification with average grain size 25 nm. The influence of the ZrO2 coating in terms of its barrier properties for corrosion in quasiphysiological 0.9% NaCl solution has been studied. Electrochemical measurements indicated good barrier properties of the coating on specimens in the physiological solution environment

    Constitutive behavior of as-cast A356

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    The constitutive behavior of aluminum alloy A356 in the as-cast condition has been characterized using compression tests performed over a wide range of deformation temperatures (30-500{\deg}C) and strain rates (\approx0.1-10 /s). This work is intended to support the development of process models for a wide range of conditions including those relevant to casting, forging and machining. The flow stress behavior as a function of temperature and strain rate has been fit to a modified Johnson-Cook and extended Ludwik-Hollomon expression. The data has also been assessed with both the strain-independent Kocks-Mecking and Zener-Hollomon frameworks. The predicted plastic flow stress for each expression are compared. The results indicate that the extended Ludwik-Hollomon is best suited to describe small strain conditions (stage III hardening), while the Kocks-Mecking is best employed for large strain (stage IV). At elevated temperatures, it was found that the Zener-Hollomon model provides the best prediction of flow stress.Comment: 34 pages, 12 figure

    The carotenoid and provitamin A content of the watermelon

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    10 years ago lycopene, C40H56, and carotene, C40H56, were isolated from the pulp of the European watermelon (Citrullus vulgaris, Schrad. = Cucumis citrullus, L.) by Zechmeister and Tuzson (l), and it was shown that the chief pigment, lycopene, is responsible for the red color. As the chromatographic method was not available at that time, no precise information as to the composition of the pigment was obtained. In some new experiments described below we have carried out a quantitative analysis of the components and have estimated the provitamin A content of the California watermelon. 1 kilo of the pulp examined contained 1.0 mg. of a complicated xanthophyll mixture, 6.1 mg. of lycopene, 0.06 mg. of γ-carotene, 0.16 mg. of unknown carotenoids (located in the column between γ- and β-carotene), 0.46 mg. of β-carotene, 0.01 mg. of α-carotene. The figures include the fractions of lycopene, and γ- and β-carotene which underwent isomerization during the experimental procedure (2). The calorimetric value of the total extract of 1 kilo of pulp corresponded to 7 to 8 mg. of “lycopene”; some samples were, however, considerably richer in pigment. Our material, picked in California in September, contained, according to the above figures, 0.5 mg. of provitamin A in 1 kilo of pulp, or about one-fifth to one-sixth of the daily β-carotene requirement of an adult person. It is interesting to note that a considerable number of yellow and pink unidentified oxygen-containing carotenoids were found in minute quantities; i.e., to the extent of about 0.01 mg. per kilo of pulp. Even with the use of chromatography 1000 or more kilos of melon would be needed for a satisfactory study of these pigments. One of them is spectroscopically identical with torulene, detected by Lederer in red yeast (3)

    Chemical composition, antioxidant effects and antimicrobial activities of some spices’ essential oils on food pathogenic bacteria

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    Thymus vulgaris, Cinnamomum zeylanicum and Ocimum gratissimum are spices widely used as aroma enhancers and food preservatives. This work assessed the chemical composition, antioxidant and antimicrobial effect of their essential oils on some food pathogenic bacteria, namely, Staphylococcus aureus, Citrobacter freundii, Enterobacter cloacae, Morganella morganii, Escherichia coli, Salmonella typhimurium, Proteus vulgaris and Shigella flexineri. After chemical analyses of the essential oils by gas chromatography and gas chromatography coupled to mass spectroscopy, the antimicrobial effects were subsequently assessed by disk and microdilution methods, while the antioxidant evaluations were performed by free radical scavenging activity. T. vulgaris essential oil composed of p-cymene (45.90%) and thymol (23.72%) which exhibited the highest inhibitory diameters of 20.33±0.58 and 18.00±1 mm, respectively, on the growth of S. aureus and C. freundii. O. gratissimum essential oil with thymol as major compound (47.11%) was more active to inhibit the growth of C. freundii and S. flexineri with respective inhibitory diameters of 18±1.73 and 16±2 mm. Essential oil from dry leaves of C. zeylanicum containing cinnamaldehyde (82.23%) and linalool (12.12%) was found to have the lowest values for minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) (≤3.53 mg/mL)considering the growth of S. flexineri, C. freundii and E. cloacae. Regarding the antioxidant effect, C. zeylanicum and T. vulgaris essential oil showed the most scavenging effect with half-maximal DPPH scavenging concentration (SC50) of 2.5 × 10-5 and 6.5 × 10-5 mg/ml, respectively. Their antioxidant effects were higher than conventionally used antioxidants in food products, butylhydroxyltoluene (BHT) and vitamin C.Key words: Spices, essential oils, chemical composition, antibacterial and antioxidant effects

    Discrepant Expectations About Benefits and Harms

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    HST Studies of the WLM Galaxy. I. The Age and Metallicity of the Globular Cluster

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    We have obtained V and I images of the lone globular cluster that belongs to the dwarf Local Group irregular galaxy known as WLM. The color-magnitude diagram of the cluster shows that it is a normal old globular cluster with a well-defined giant branch reaching to M_V=-2.5, a horizontal branch at M_V=+0.5, and a sub-giant branch extending to our photometry limit of M_V=+2.0. A best fit to theoretical isochrones indicates that this cluster has a metallicity of [Fe/H]=-1.52\pm0.08 and an age of 14.8\pm0.6 Gyr, thus indicating that it is similar to normal old halo globulars in our Galaxy. From the fit we also find that the distance modulus of the cluster is 24.73\pm0.07 and the extinction is A_V=0.07\pm0.06, both values that agree within the errors with data obtained for the galaxy itself by others. We conclude that this normal massive cluster was able to form during the formation of WLM, despite the parent galaxy's very small intrinsic mass and size.Comment: 14 pages, 5 figures, 1 tabl

    Prolycopene, a Naturally Occurring Stereoisomer of Lycopene

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    In this paper we record the observation that there occurs in the variety of tomato called "tangerine tomato" a carotenoid, prolycopene, which is an isomer of lycopene; the isomeric relationship is similar to that between lycopene and neolycopene,I and in our opinion prolycopene is to be classed as a naturally occurring neolycopene, being the first observed natural neo form of a C40-carotenoid
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