排序方式: 共有23条查询结果,搜索用时 343 毫秒
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S. GeorgescuO. Toma A.M. VoiculescuC. Matei R. BirjegaL. Petrescu 《Physica B: Condensed Matter》2012,407(7):1124-1127
Bright green (at 525 and 550 nm) and red (at 660 nm) luminescence in Er:Yb:La3Ga5.5Ta0.5O14 (LGT) powder synthesized by solid state reaction was obtained by pumping at 936 nm. Yb3+-Er3+ energy transfer processes accounting for population of the 2H211/2, 4S3/2 and 4F9/2 Er3+ levels are discussed. The dependence of ratio between the intensities of the green and red luminescence on pump intensity is analyzed. The rather high quantum efficiency (58%) of the (4S3/2, 2H211/2) Er3+ emitting level recommends LGT doped with erbium and ytterbium for upconversion applications. 相似文献
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Bandichhor R Petrescu AD Vespa A Kier AB Schroeder F Burgess K 《Journal of the American Chemical Society》2006,128(33):10688-10689
A special, water-soluble, fluorescent probe 1 was designed. This consisted of a fluorescein-based component to harvest irradiation at 488 nm and a rhodamine-based part designed to emit it at a significantly longer wavelength. This cassette was used to label an illustrative protein called ACBP. Evidence was accumulated to support the assertion that ACBP-1 bound its native ligand with a binding constant similar to that of the unlabeled protein, and retained its secondary structure (CD). ACBP-1 was imported into cells using the Chariot peptide. Confocal images proved that some ACBP-1 localized into the nucleus (as expected) and, most significantly, it could be visualized more effectively by irradiating at the donor (fluorescein-like) part of the cassette, than the acceptor (rhodamine-like) part. Overall, this study demonstrates that cassettes of this kind can label a protein without significantly perturbing its function or secondary structure and they can be visualized effectively via irradiation of the donor and observation of the acceptor fluorescence. 相似文献
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The magnitudes of the two spin-spin coupling constants J(N1H …? 13C), and all relatives signs of the couplings J(1H …? 1H) and J(1H …? 13C) of formamide-14N, were determined by triple resonance experiments of the types 1H—{13C}—{14N} and 1H—{1H}—{14N}. 相似文献
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Monica Costea Stoian Petrescu Michel Feidt Catalina Dobre Bogdan Borcila 《Entropy (Basel, Switzerland)》2021,23(5)
An irreversible Carnot cycle engine operating as a closed system is modeled using the Direct Method and the First Law of Thermodynamics for processes with Finite Speed. Several models considering the effect on the engine performance of external and internal irreversibilities expressed as a function of the piston speed are presented. External irreversibilities are due to heat transfer at temperature gradient between the cycle and heat reservoirs, while internal ones are represented by pressure losses due to the finite speed of the piston and friction. Moreover, a method for optimizing the temperature of the cycle fluid with respect to the temperature of source and sink and the piston speed is provided. The optimization results predict distinct maximums for the thermal efficiency and power output, as well as different behavior of the entropy generation per cycle and per time. The results obtained in this optimization, which is based on piston speed, and the Curzon–Ahlborn optimization, which is based on time duration, are compared and are found to differ significantly. Correction have been proposed in order to include internal irreversibility in the externally irreversible Carnot cycle from Curzon–Ahlborn optimization, which would be equivalent to a unification attempt of the two optimization analyses. 相似文献
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E. M. Anghel A. Georgiev S. Petrescu R. Popov M. Constantinescu 《Journal of Thermal Analysis and Calorimetry》2014,117(2):557-566
Three phase change paraffinic materials (PCMs) were thermophysically (phase-transition temperatures, latent heat, heat capacity at constant pressure, density, and thermal conductivity) investigated in order to be used as latent heat storage media in a pilot plant developed in Plovdiv Bulgaria. Raman structural investigation probes aliphatic character of the E53 sample, while the E46 and ECP samples contain also unsaturated components due to their Raman features within 1,500–1,700 cm?1 range. Orthorhombic structure of the three PCMs was evidenced by the Raman modes at the 1,417 cm?1. The highest latent heat value, ΔH, of phase transitions among the three materials was represented by summation of a solid order–disorder, and melting latent heat was encountered by the E53 paraffin, i.e., 194.32 J g?1 during a μ-DSC scan of 1 °C min?1. Conversely, the ECP composite containing ceresin component shows the lowest latent heat value of 143.89 J g?1 and the highest thermal conductivity of 0.46 W m?1 K?1 among the three phase change materials (PCMs). More facile melt-disordered solid transition with the activation energy of 525.45 kJ mol?1 than the lower temperature transition of disorder–order (E a of 631.73 kJ mol?1) during the two-step process of solidification for the E53 melt are discussed in terms of structural and molecular motion changes. 相似文献
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Constantin Roşu Doina Mănăila-Maximean Rodica Bena Emil Petrescu Stanislav Klosowicz Krzysztof L. Czuprynski 《Czechoslovak Journal of Physics》2003,53(3):235-247
Polymer-dispersed-liquid-crystal films were obtained using the photopolymerization-induced-phase-separation method. The thermally stimulated depolarization current measurements indicate a space-charge-limited current. Conduction of electronic type was proven and the activation energy, specific to the conduction process, was calculated. Optical measurements have been performed simultaneously with the measurements of thermally stimulated currents and the nematic-isotropic phase transition was detected by the switch of the optical transmission. The change of the optical transmission versus applied a.c. voltage was the indication for the on-off switch behavior, useful in electro-optic applications. 相似文献
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A. Matei M. Zamfirescu C. Radu M. Dinescu E. C. Buruiana T. Buruiana L. E. Sima S. M. Petrescu 《Applied Physics A: Materials Science & Processing》2011,104(3):821-827
Hybrid methacrylates based on silane derivates (ormosils) have been considered for applications in electronics, microtechnology,
corrosion resistant coatings, dentistry, and biomedical implants. The presence of both inorganic chains, responsible for chemical
and thermal stability, hardness, and transparency, and organic groups, which bring new advantages such as the possibility
of functionalization and easy, low temperature processing, can result in the appearance of unique properties. 相似文献
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Identification and structural characterization of novel O‐ and N‐glycoforms in the urine of a Schindler disease patient by Orbitrap mass spectrometry 下载免费PDF全文
Mirela Sarbu Cristian V. A. Munteanu Liana Dehelean Andrei J. Petrescu Jasna Peter‐Katalinic Alina D. Zamfir 《Journal of mass spectrometry : JMS》2015,50(9):1044-1056
Schindler disease is an inherited metabolic disorder caused by the deficient activity of α‐N‐acetylgalactosaminidase enzyme. An accurate diagnosis requires, besides clinical examination, complex and costly biochemical and molecular genetic tests. In the last years, mass spectrometry (MS) based on nanofluidics and high‐resolution instruments has become a successful alternative for disease diagnosis based on the investigation of O‐glycopeptides in patient urine. A complex mixture of glycoforms extracted from the urine of a 3‐year‐old patient was investigated by Orbitrap MS equipped with Nanospray Flex Ion Source in the negative ion mode. For structural characterization of several molecular species, collision‐induced dissociation MS2–MS3 was carried out using collision energy values within 20–60 eV range. By our approach, 39 novel species associated to this condition were identified, among which O‐glycopeptides, free O‐glycans and one structure corresponding to an N‐glycan never characterized in the context of Schindler disease. The experiments conducted at a resolution of 60 000 allowed the discrimination and identification of a total number of 69 different species with an average mass accuracy of 9.87 ppm, an in‐run reproducibility of almost 100%, an experiment‐to‐experiment and day‐to‐day reproducibility of about 95%. This study brings contributions in the diagnosis of Schindler disease through the elucidation of potential biomarker species in urine. Our multistage MS results completed with 39 new glycoforms the inventory of potential biomarker structures associated to Schindler disease. For the first time, an N‐glycan was identified and structurally characterized in Schindler patient urine, which opens new research directions in the field. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献