801 research outputs found

    Automorphisms of C-k with an invariant non-recurrent attracting Fatou component biholomorphic to C x (C*)(k-1)

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    We prove the existence of automorphisms of C-k , k >= 2, having an invariant, non-recurrent Fatou component biholomorphic to C x (C*)(k-1) which is attracting, in the sense that all the orbits converge to a fixed point on the boundary of the component. As a corollary, we obtain a Runge copy of C x (C*)(k-1) in C-k. The constructed Fatou component also avoids k analytic discs intersecting transversally at the fixed point

    A Bacillus subtilis cell fraction (BCF) inducing calcium carbonate precipitation: biotechnological perspectives for monumental stone reinforcement

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    Abstract Monumental stone decay is a consequence of the weathering action of physical, chemical and biological factors, which induce a progressive increase in porosity. To cope this degradation, bacterial calcium carbonate mineralization has been proposed as a tool for the conservation of monumental calcareous stones. The advantage of this kind of treatment is to obtain a mineral product similar to the stone substrate, mimicking the natural process responsible for stone formation. In this work, the possibility to induce CaCO3 mineralization by a bacteria-mediated system in absence of viable cells was investigated and tested on stone. Our results showed that Bacillus subtilis dead cells as wells as its bacterial cell wall fraction (BCF) can act as calcite crystallization nuclei in solution. BCF consolidating capability was further tested in laboratory on slab stones, and in situ on the Angera Church, a valuable 6th century monumental site. New crystals formation was observed inside pores and significant decrease in water absorption (up to 16.7%) in BCF treated samples. A little cohesion increase was observed in the treated area of the Angera Church, showing the potential of this application, even though further improvements are needed

    Screening of Nuclear Reactions in the Sun and Solar Neutrinos

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    We quantitatively determine the effect and the uncertainty on solar neutrino production arising from the screening process. We present predictions for the solar neutrino fluxes and signals obtained with different screening models available in the literature and by using our stellar evolution code. We explain these numerical results in terms of simple laws relating the screening factors with the neutrino fluxes. Futhermore we explore a wider range of models for screening, obtained from the Mitler model by introducing and varying two phenomenological parameters, taking into account effects not included in the Mitler prescription. Screening implies, with respect to a no-screening case, a central temperat reduction of 0.5%, a 2% (8%) increase of Beryllium (Boron)-neutrino flux and a 2% (12%) increase of the Gallium (Chlorine) signal. We also find that uncertainties due to the screening effect ar at the level of 1% for the predicted Beryllium-neutrino flux and Gallium signal, not exceeding 3% for the Boron-neutrino flux and the Chlorine signal.Comment: postscript file 11 pages + 4 figures compressed and uuencoded we have replaced the previous paper with a uuencoded file (the text is the same) for any problem please write to [email protected]

    Role of virtual break-up of projectile in astrophysical fusion reactions

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    We study the effect of virtual Coulomb break-up, commonly known as the dipole polarizability, of the deuteron projectile on the astrophysical fusion reaction 3He(d,p)4He. We use the adiabatic approximation to estimate the potential shift due to the E1 transition to the continuum states in the deuteron, and compute the barrier penetrability in the WKB approximation. We find that the enhancement of the penetrability due to the deuteron break-up is too small to resolve the longstanding puzzle observed in laboratory measurements that the electron screening effect is surprisingly larger than theoretical prediction based on an atomic physics model. The effect of the 3He break-up in the 3He(d,p)4He reaction, as well as the 7Li break-up in the 7Li(p,alpha)4He reaction is also discussed.Comment: 9 pages, 2 eps figure

    Target-Selective Drug Delivery through Liposomes Labeled with Oligobranched Neurotensin Peptides.

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    The structure and the in vitro behavior of liposomes filled with the cytotoxic drug doxorubicin (Doxo) and functionalized on the external surface with a branched moiety containing four copies of the 8-13 neurotensin (NT) peptide is reported. The new functionalized liposomes, DOPC-NT(4) Lys(C(18) )(2) , are obtained by co-aggregation of the DOPC phospholipid with a new synthetic amphiphilic molecule, NT(4) Lys(C(18) )(2) , which contains a lysine scaffold derivatized with a lipophilic moiety and a tetrabranched hydrophilic peptide, NT8-13, a neurotensin peptide fragment well known for its ability to mimic the neurotensin peptide in receptor binding ability. Dynamic light scattering measurements indicate a value for the hydrodynamic radius (RH) of 88.3±4.4 nm. The selective internalization and cytotoxicity of DOPC-NT(4) Lys(C(18) )(2) liposomes containing Doxo, as compared to pure DOPC liposomes, were tested in HT29 human colon adenocarcinoma and TE671 human rhabdomyosarcoma cells, both of which express neurotensin receptors. Peptide-functionalized liposomes show a clear advantage in comparison to pure DOPC liposomes with regard to drug internalization in both HT29 and TE671 tumor cells: FACS analysis indicates an increase in fluorescence signal of the NT(4) -liposomes, compared to the DOPC pure analogues, in both cell lines; cytotoxicity of DOPC-NT(4) Lys(C(18) )(2) -Doxo liposomes is increased four-fold with respect to DOPC-Doxo liposomes in both HT29 and TE671 cell lines. These effects could to be ascribed to the higher rate of internalization for DOPC-NT(4) Lys(C(18) )(2) -Doxo liposomes, due to stronger binding driven by a lower dissociation constant of the NT(4) -liposomes that bind the membrane onto a specific protein, in contrast to DOPC liposomes, which approach the plasma membrane unselectively

    Fatou flowers and parabolic curves

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    In this survey we collect the main results known up to now (July 2015) regarding possible generalizations to several complex variables of the classical Leau-Fatou flower theorem about holomorphic parabolic dynamics

    Fusion rate enhancement due to energy spread of colliding nuclei

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    Experimental results for sub-barrier nuclear fusion reactions show cross section enhancements with respect to bare nuclei which are generally larger than those expected according to electron screening calculations. We point out that energy spread of target or projectile nuclei is a mechanism which generally provides fusion enhancement. We present a general formula for calculating the enhancement factor and we provide quantitative estimate for effects due to thermal motion, vibrations inside atomic, molecular or crystal system, and due to finite beam energy width. All these effects are marginal at the energies which are presently measurable, however they have to be considered in future experiments at still lower energies. This study allows to exclude several effects as possible explanation of the observed anomalous fusion enhancements, which remain a mistery.Comment: 17 pages with 3 ps figure included. Revtex styl

    Muonic hydrogen cascade time and lifetime of the short-lived 2S2S state

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    Metastable 2S{2S} muonic-hydrogen atoms undergo collisional 2S{2S}-quenching, with rates which depend strongly on whether the ÎŒp\mu p kinetic energy is above or below the 2S→2P{2S}\to {2P} energy threshold. Above threshold, collisional 2S→2P{2S} \to {2P} excitation followed by fast radiative 2P→1S{2P} \to {1S} deexcitation is allowed. The corresponding short-lived ÎŒp(2S)\mu p ({2S}) component was measured at 0.6 hPa H2\mathrm{H}_2 room temperature gas pressure, with lifetime τ2Sshort=165−29+38\tau_{2S}^\mathrm{short} = 165 ^{+38}_{-29} ns (i.e., λ2Squench=7.9−1.6+1.8×1012s−1\lambda_{2S}^\mathrm{quench} = 7.9 ^{+1.8}_{-1.6} \times 10^{12} \mathrm{s}^{-1} at liquid-hydrogen density) and population Ï”2Sshort=1.70−0.56+0.80\epsilon_{2S}^\mathrm{short} = 1.70^{+0.80}_{-0.56} % (per ÎŒp\mu p atom). In addition, a value of the ÎŒp\mu p cascade time, TcasÎŒp=(37±5)T_\mathrm{cas}^{\mu p} = (37\pm5) ns, was found.Comment: 4 pages, 3 figure

    Chest CT texture-based radiomics analysis in differentiating COVID-19 from other interstitial pneumonia

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    Purpose To evaluate the potential role of texture-based radiomics analysis in differentiating Coronavirus Disease-19 (COVID-19) pneumonia from pneumonia of other etiology on Chest CT. Materials and methods One hundred and twenty consecutive patients admitted to Emergency Department, from March 8, 2020, to April 25, 2020, with suspicious of COVID-19 that underwent Chest CT, were retrospectively analyzed. All patients presented CT findings indicative for interstitial pneumonia. Sixty patients with positive COVID-19 real-time reverse transcription polymerase chain reaction (RT-PCR) and 60 patients with negative COVID-19 RT-PCR were enrolled. CT texture analysis (CTTA) was manually performed using dedicated software by two radiologists in consensus and textural features on filtered and unfiltered images were extracted as follows: mean intensity, standard deviation (SD), entropy, mean of positive pixels (MPP), skewness, and kurtosis. Nonparametric Mann–Whitney test assessed CTTA ability to differentiate positive from negative COVID-19 patients. Diagnostic criteria were obtained from receiver operating characteristic (ROC) curves. Results Unfiltered CTTA showed lower values of mean intensity, MPP, and kurtosis in COVID-19 positive patients compared to negative patients (p = 0.041, 0.004, and 0.002, respectively). On filtered images, fine and medium texture scales were significant differentiators; fine texture scale being most significant where COVID-19 positive patients had lower SD (p = 0.004) and MPP (p = 0.004) compared to COVID-19 negative patients. A combination of the significant texture features could identify the patients with positive COVID-19 from negative COVID-19 with a sensitivity of 60% and specificity of 80% (p = 0.001). Conclusions Preliminary evaluation suggests potential role of CTTA in distinguishing COVID-19 pneumonia from other interstitial pneumonia on Chest CT
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