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  • 1
    Electronic Resource
    Electronic Resource
    Chaos and dynamical coexistence in Lennard-Jones clusters (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 6861-6867 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The chaotic dynamics in Lennard-Jones microclusters is revisited for sizes ranging from 3 to 147 monomers. We calculate the largest Liapunov exponent λ in classical molecular dynamics simulations at several total energies, carefully looking at the convergence of λ. Contrary to previous results, no evidence for any distinct signature of the solid-liquid phase transition is found in the variations of λ versus E for clusters smaller than 38 atoms (except LJ3). Larger clusters with 38, 55 and 147 atoms undergo a clear but continuous increase of λ above the freezing energy. This increase occurs simultaneously with a drop in the kinetic temperature between the freezing and melting energies. Hence dynamical coexistence appears to smooth the strong variations of λ near melting. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476100
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  • 2
    Electronic Resource
    Electronic Resource
    Structural transitions in nitrogen molecular clusters: Experiment and simulation (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 4650-4658 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structure of (N2)n clusters is investigated up to the size of several hundred molecules with means of electron diffraction experiments and numerical simulations. The comparison relies on the calculated diffraction patterns. The structures extracted numerically are obtained with a global optimization procedure. Two transformations are observed. The first one is the transition from polyicosahedral to multilayer icosahedral. It is seen from simulations to occur near the crossover size n*∼40 molecules, but is hardly seen in the experiment. The second one is the transition from icosahedral to cubic. In this case, both approaches indicate a crystalline crossover size nc located near 150–200 molecules. However, while the structures resulting from global optimization clearly show the enhanced stability of perfect cubic structures at zero temperature above nc, the information obtained from experimental diffraction functions at finite temperature and pressure exhibits a more progressive appearance of the crystalline features. This suggests the presence of significant defects in the real structure of nitrogen molecular clusters as they undergo their transformation toward the bulk face-centered-cubic geometry. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479226
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of in vitro culture of HIV-negative Kaposi’s sarcoma-derived cells. In vitro responses to alfa interferon (1997)
    Springer
    Archives of dermatological research 289 (1997), S. 421-428 
    Details
    ISSN: 1432-069X
    Keywords: Key words Kaposi’s sarcoma-derived cells ; Alfa ; interferon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We established long-term cultures from skin tumors of nine patients suffering from classical Kaposi’s sarcoma (KS). Spindle cells obtained after enzymatic digestion were cultured on gelatin- or fibronectin-coated flasks in DMEM with 15% fetal calf serum, aFGF and heparin. Immunohistochemical staining was positive for MHC class I, laminin, type IV collagen, vimentin, α smooth muscle actin (20–40% of cells), caldesmon (20%), calponin (20–40%) and smooth muscle myosin (20–40%), and was negative for common leukocyte antigen, CD4, LFA1, CD34 and cytokeratin. Around 20% of cells up to the third passage in culture expressed the endothelial markers CD36, BMA 120 but were negative for UEA and Fc von Willebrand. Smooth muscle proteins were detected with immunoblotting. Using the polymerase chain reaction, human herpes virus 8 (HHV8) sequences were detected in primary cultures of three out of seven cell lines but were rapidly lost during in vitro passaging. KS-derived cells did not proliferate in serum-free medium, had a normal karyotype and did not grow in soft agar medium. Tumors formed in nude mice injected with KS-derived cells. The tumors were composed of mouse cells and were highly vascularized. Our results suggest that KS-derived cells are heterogeneous: the majority of cells have either a smooth muscle cell or a fibroblastic phenotype. Another minor cell compartment was composed of endothelium-derived cells. KS cells do not possess the characteristics of transformed cells in vitro and may be composed of polyclonal activated cells. Recombinant α interferon (rIFN) slightly inhibited the growth of KS-derived cells and increased the expression of MHC class I antigens. While cells were resistant to natural killer (NK) cell-mediated cytotoxicity, they became sensitive to rIFN-primed NK cells. Thus, the antitumor potential of rIFN against KS in vivo could result from immunomodulatory rather than from direct antiproliferative effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004030050215
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  • 4
    Electronic Resource
    Electronic Resource
    Biodistribution of iodine-125 tyramine transforming growth factor α antisense oligonucleotide in athymic mice with a human mammary tumour xenograft following intratumoral injection (1996)
    Springer
    European journal of nuclear medicine 23 (1996), S. 448-452 
    Details
    ISSN: 1619-7089
    Keywords: Transforming growth factor α ; Antisense phosphodiester oligonucleotide ; Radioiodine labelling ; Biodistribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The Watson-Crick base pairing rule provides the underlying principle for the antisense (AS) approach to inhibiting gene expression. Transforming growth factor α (TGFα) was the first growth factor to be associated with tumorigenesis, thus making the TGFα (mRNA) a potential target for AS therapy and offering the potential for monitoring of the progression of malignancy by non-invasive imaging with radiolabelled AS phosphodiester. Probe labelling and biodistribution were studied in the present report. A 23-mer oligonucleotide sequence was synthesized and grafted in 5′ with a tyramine group which was further radioiodinated. The radiolabelled AS was injected intratumorally in mammary tumour-bearing BALB/c mice (3 weeks after inoculation of 7·106 NS2T2A mammary cells). Biodistribution was monitored by sequential scintigraphy and organ radioactivity after autopsy. The 5′ tyramine group allowed specific and stable radiolabelling of the AS with125I. The125I AS oligonucleotide was rapidly cleared from the tumour by intestine and kidneys. Four hours after intratumoral injection, 6.5%±1.5% of the dose was retained in the tumour as non-degraded125I AS. It is concluded that 5′ tyraminylated AS provides information on the biodistribution of AS oligonucleotide following intratumoral injection. These data will contribute to the pharmacology of AS oligonucleotides which can be used for therapy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01247375
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  • 5
    Electronic Resource
    Electronic Resource
    Structure of nitrogen molecular clusters (N2)n with 13≤n≤55 (1999)
    Springer
    The European physical journal 9 (1999), S. 189-193 
    Details
    ISSN: 1434-6079
    Keywords: PACS: 36.40.Mr Spectroscopy and geometrical structure of clusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We investigate the structural properties of nitrogen molecular clusters (N2) n using classical Monte Carlo simulations and optimization methods. As is the case for argon clusters, we find polyicosahedral (anti-Mackay) geometries above 13 molecules, and multilayer icosahedra with uncomplete outer shell (Mackay) geometries below 55 molecules. The crossover point between these two kinds of structures is located near 42 molecules, whereas it is at only 31 for argon. With a simple three-body (Axilrod–Teller) potential added to the standard Lennard–Jones model, we interpret this difference as the result of the strong anisotropy of the molecular potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530050424
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  • 6
    Electronic Resource
    Electronic Resource
    Anaerobic threshold in children: determination from saliva analysis in field tests (1995)
    Springer
    European journal of applied physiology 70 (1995), S. 541-544 
    Details
    ISSN: 1439-6327
    Keywords: Exercise ; Children ; Physiological evaluation ; Lactate threshold
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to determine the anaerobic threshold of children by the analysis of saliva collected during field tests. A group of 25 children (mean age, 10.5 years) performed an incremental exercise test on a track, consisting of 4-min stages at increasing running velocities. Before each test (at rest) and at the end of each stage, both blood (via finger pricks) and saliva samples (for measurement of salivary concentrations of Na+ and Cl−) were collected to determine lactate threshold (Th1a-) and saliva threshold (Thsa), respectively. There were no significant differences between values of Th1a- and Thsa when expressed either as running velocity [mean Th1a-, 10.73 (SD 1.96) km · h−1; mean Thsa, 10.89 (SD 1.69) km · h−1] or heart rate [Th1a-, 182(SD 14) beats · min−1 Thsa 183 (SD 11) beats · min−1]. In addition, correlations between Thsa and Th1a were high, when both values were expressed as running velocity in kilometres per hour (r = 0.89;P 〈 0.001), or heart rate in beats per minute (r = 0.90;P 〈 0.001). In conclusion, these findings suggested that saliva analysis would be a valid method for anaerobic threshold determination in field tests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00634384
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  • 7
    Electronic Resource
    Electronic Resource
    Monte-Carlo simulations of rotating clusters (1998)
    Springer
    The European physical journal 3 (1998), S. 229-236 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 36.40.Ei Phase transitions in clusters- 82.30.Qt Isomerization and rearrangement- 05.20.Gg Classical ensemble theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A new scheme for estimating densities of states at non zero angular momentum is proposed, using the Monte-Carlo (MC) and multiple histogram methods. It is based on a rigorous expression of the classical density of states for a rotating system. Two features appear: the centrifugal energy ( angular momentum and I the instantaneous inertia tensor in the center of mass reference frame) is added to the potential energy and the configurational densities of states is weighted by . Comparing the MC results for the 13-atom Lennard-Jones cluster and a calculation based on molecular dynamics (MD) shows that this weight is important if the rotation induces a structural change at a finite temperature. The MC algorithm proves to be much more efficient than MD, even at finite .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530050170
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