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  • 1
    ISSN: 1432-2242
    Keywords: Key words Azolla ; Cyanobacteria-Symbiosis ; Parsimony ; PCR-fingerprinting ; STRR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Symbiotically associated cyanobacteria from 18 accessions within all known species in the genus Azolla were examined and classified by the use of polymerase chain reaction (PCR)-fingerprinting. A repetitive sequence specific for cyanobacteria, the short tandemly repeated repetitive (STRR) sequence, was used as a primer in the reaction. Cyanobacterial filaments isolated directly from the Azolla leaf cavity or contained within homogenised symbiotic Azolla tissue were used as templates. Based on the fingerprint pattern, distinct differences were demonstrated between cyanobacteria isolated from the Euazolla and Rhizosperma sections. In addition, individual fingerprints were obtained from all cyanobacteria isolated from the different Azolla species. The fingerprints were used to generate a phylogenetic tree. Three clusters were distinguished: one contained the four isolates from the section Euazolla, a second the isolate from Azolla filiculoides, and a third the three isolates from the section Rhizosperma. By the use of STRR-PCR fingerprinting, new data on the taxonomy of cyanobacteria in Azolla were obtained, which have been difficult to generate by other classification methods. PCR-fingerprinting may, therefore, be a valuable tool for diversity and classification studies of symbiotic cyanobateria from Azolla and, as co-evolution between the cyanobacteria and its corresponding host exists the method may also be useful for the taxonomy of Azolla.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0630
    Keywords: PACS: 82.40.Tc; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Photoluminescence studies on porous silicon show that there are luminescence centers present in the surface states. By taking photoluminescence spectra of porous silicon with respect to temperature, a distinct peak can be observed in the temperature range 100–150 K. Both linear and nonlinear relationships were observed between excitation laser power and the photoluminescence intensity within this temperature range. In addition, there was a tendency for the photoluminescence peak to red shift at low temperature as well as at low excitation power. This is interpreted as indicating that the lower energy transition becomes dominant at low temperature and excitation power. The presence of these luminescence centers can be explained in terms of porous silicon as a mixture of silicon clusters and wires in which quantum confinement along with surface passivation would cause a mixing of Γ and X band structure between the surface states and the bulk. This mixing would allow the formation of luminescence centers.
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  • 3
    ISSN: 1432-0630
    Keywords: 82.40.Tc ; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Photoluminescence studies on porous silicon show that there are luminescence centers present in the surface states. By taking photoluminescence spectra of porous silicon with respect to temperature, a distinct peak can be observed in the temperature range 100–150 K. Both linear and nonlinear relationships were observed between excitation laser power and the photoluminescence intensity within this temperature range. In addition, there was a tendency for the photoluminescence peak to red shift at low temperature as well as at low excitation power. This is interpreted as indicating that the lower energy transition becomes dominant at low temperature and excitation power. The presence of these luminescence centers can be explained in terms of porous silicon as a mixture of silicon clusters and wires in which quantum confinement along with surface passivation would cause a mixing of Γ andX band structure between the surface states and the bulk. This mixing would allow the formation of luminescence centers.
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  • 4
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Bent triangular Si crystals with an oblique-cut angle 12.16° are used on the beamline 4W1C at Beijing Synchrotron Radiation Facility, to select monochromatic x-rays and to focus the beam in the horizontal direction. The downstream Pt-coated reflective mirror is bent as a cylindroid focuses the beam vertically. Double-focused monochromatic x rays are available on the diffuse scattering station. Specifications of the beamline with the Si (220) monochromator were measured as follows: size of the focus spot—0.5 mm (horizontal)×0.3 mm (vertical), maximum x-ray density—1.6×109 photons/s mm2, and energy resolution of the monochromatic beam—4.4×10−4. © 1995 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2532-2534 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the influence of deposition parameters on stress generation in CNx (0.3〈x〈0.5) thin films deposited onto Si(001) substrates by reactive magnetron sputtering of C in pure N2 discharges. Film stress, σ, which in all cases is compressive, decreases with an increase in the N2 pressure, PN2, due to structural changes induced by the pressure-dependent variation in the average energy of particles bombarding the film during deposition. The film stress σ is also a function of the film growth temperature, Ts, and exhibits a maximum value of ∼5 GPa at 350 °C. Under these conditions, the films have a distorted microstructure consisting of a three-dimensional, primarily sp2 bonded, network. In contrast, films deposited at Ts〈200 °C with a low stress are amorphous. At 350 °C〈Ts〈600 °C, σ gradually decreases as Ts is increased and the microstructure becomes more graphitic and contains fewer defects. Nanoindentation measurements show that the films grown at 350 °C exhibit the highest hardness and elasticity. © 1998 American Institute of Physics.
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  • 6
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Considerable progress in the investigation of the electronic and vibrational properties of atoms, molecules, materials, surfaces and interfaces has been achieved by combining different photon sources of complementary characteristics. In this paper some experimental results obtained recently at LURE by using two synchronized sources, such as the IR free-electron laser (FEL) CLIO, the VUV storage ring FEL, synchrotron radiation and table lasers, are presented. Using CLIO synchronized with a YAG laser allows the investigation of the vibrational properties of adsorbed species by the non-linear optical technique of visible–IR sum (difference) frequency generation, as shown for the adsorption of hydrogen on platinum in the electrochemical environment. The second result reported here relates to the study of the intersubband stimulated emission in GaAs/GaAlAs quantum wells by pump-probe experiments using the two-colour configuration of CLIO. The combination of a mode-locked Ar+ laser and synchrotron radiation has been used for investigations in a pump-probe arrangement of the ionization of Xe atoms via the resonant state Xe* 5p55d [3/2]1. The final example is a time-resolved core-level spectroscopy study of photoexcited Si(111) 2 × 1 surfaces by using a combination of the naturally synchronized UV storage ring laser and synchrotron radiation.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Histopathology 35 (1999), S. 0 
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Overexpression of p53 has been reported in endometrial carcinomas, especially in uterine papillary serous carcinoma (UPSC), to correlate with worse prognosis. Endometrial metaplasia is commonly encountered in patients with dysfunctional uterine bleeding (DUB) and may on occasion be difficult to distinguish from atypical endometrial hyperplasia or carcinoma on biopsies. The present study was initiated in the belief that metaplastic tissue might not show overexpression of p53 and would thus help to distinguish it from carcinomas of non-endometrioid histology.〈section xml:id="abs1-2"〉〈title type="main"〉Methods    and resultsParaffin-embedded tissue of endometrial biopsies with papillary metaplasia (22 cases), tubal metaplasia (five cases) and eosinophilic meta-plasia (seven cases) from patients with DUB were immunostained for p53 immunoreactivity. No evidence of hyperplasia was noted in any of the cases selected for the study. Twenty-eight cases of UPSC were included for comparison. Our study showed p53 overexpression in 25 of 28 (89%) UPSC. Weak and heterogeneous p53 immunoreactivity was present in 10 of 22 (45%) papillary metaplasias, four of five (80%) tubal metaplasias and four of seven (57%) eosinophilic metaplasias. Follow-up of 16–45 (median 32) months was unremarkable except for one patient with eosinophilic metaplasia who had simple endometrial hyperplasia in subsequent biopsy.〈section xml:id="abs1-3"〉〈title type="main"〉ConclusionsThe presence of weak and heterogeneous p53 immunoreactivity in metaplastic endometrium is unexpected and might be a consequence of DNA damage. Intense, diffuse and homogeneous p53 staining favours carcinoma.
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  • 8
    Electronic Resource
    Electronic Resource
    Suite 500, 5th Floor, 238 Main Street, Cambridge Massachusetts 02142, USA : Blackwell Science Inc.
    ISSN: 1525-1438
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The protein product of proto-oncogene bcl-2 is thought to be involved in inhibition of apoptosis and is hormonally regulated in a variety of in vitro and in vivo experiments. The association of bcl-2 persistence and hormone receptor status was investigated by immunocytochemistry from paraffin-embedded tissue in a series of 82 women with endometrial carcinoma and 20 women with benign endometrium. In benign endometrium, bcl-2 immunoreactivity was strongly present in glands of proliferative and hyperplastic endometrium, while a weak signal was detected in secretory endometrium. Bcl-2 expression tends to decrease in staining intensity with progression from benign endometrium, including proliferative and hyperplastic endometrium, to endometrioid carcinoma and to mucinous, clear cell and serous carcinomas of the endometrium. Bcl-2 persistence was observed in the majority (65%) of endometrial carcinomas. We demonstrated a significant correlation of bcl-2 immunoreactivity with estrogen receptor (P = 0.000005) and progesterone receptor status (P = 0.00032). The bcl-2 persistence was found to be significantly higher in FIGO G1 and G2 tumors than in G3 tumors (P = 0.00035), while no significant difference was detected in tumors of different stages. We conclude that bcl-2 persistence is highly correlated with the presence of hormone receptors and may be hormone-dependent or related to hormonal regulation in endometrial carcinomas. Persistent expression of bcl-2 in normal and hyperplastic endometrium and endometrial carcinoma suggests that failure to inactivate bcl-2 expression early in the development of endometrial carcinoma may provide an opportunity for accumulating genetic mutations and evolution from a precursor lesion to invasive carcinoma.
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  • 9
    ISSN: 0887-6266
    Keywords: miscibility ; P3OT/EVA blends ; solvatochromatic shift ; solid state ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mixing of electrically conducting polymers in the undoped state with flexible polymers has been limited due to the stiffness of the delocalized coplanar backbone. The substitution with alkyl side chains has resulted in the distortion of the aromatic rings in the backbone with an increase of the flexibility. The alkyl substituents also prevent the thiophene back-bones from packing together, thus making blending with other polymers promising. We have investigated the phase behavior of poly(3-octylthiophene) (P3OT) with a flexible polymer, poly(ethylene-co-vinylacetate) (vinylacetate composition 20%, EVA20), and defined a miscibility window based on melting point data, on cloud point measurements, and on analysis by optical microscopy. The miscible region has been studied by UV-VIS and CPMAS NMR spectroscopies. A UV absorption in the visible region originates from a π-π * transition in the delocalized structure of P3OT, and a change in the length of the conjugated segment in the backbone results in a shift of this absorption. A gradual solvatochromatic shift of P3OT in the solid state with dilution was observed in the miscible region. T1 relaxation times for the methylene carbons in solid state show a gradual change in the relaxation process as a function of composition. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 10
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An (AlAs/GaAs/AlAs/AlGaAs)/GaAs(001) double-barrier superlattice grown by molecular beam epitaxy (MBE) is studied by combining synchrotron radiation and double-crystal x-ray diffraction (DCD). The intensity of satellite peaks is modulated by the wave function of each sublayer in one superlattice period. Simulated by the x-ray dynamical diffraction theory, it is discovered that the intensity of the satellite peaks situated near the modulating wave node point of each sublayer is very sensitive to the variation of the layer structural parameters. The accurate layer thickness of each sublayer is obtained with an error less than 1 A(ring). Furthermore, x-ray kinematical diffraction theory is used to explain the modulation phenomenon. © 1996 American Institute of Physics.
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