30 research outputs found
Linear-T scattering and pairing from antiferromagnetic fluctuations in the (TMTSF)_2X organic superconductors
An exhaustive investigation of metallic electronic transport and
superconductivity of organic superconductors (TMTSF)_2PF_6 and (TMTSF)_2ClO_4
in the Pressure-Temperature phase diagram between T=0 and 20 K and a
theoretical description based on the weak coupling renormalization group method
are reported. The analysis of the data reveals a high temperature domain
(T\approx 20 K) in which a regular T^2 electron-electron Umklapp scattering
obeys a Kadowaki-Woods law and a low temperature regime (T< 8 K) where the
resistivity is dominated by a linear-in temperature component. In both
compounds a correlated behavior exists between the linear transport and the
extra nuclear spin-lattice relaxation due to antiferromagnetic fluctuations. In
addition, a tight connection is clearly established between linear transport
and T_c. We propose a theoretical description of the anomalous resistivity
based on a weak coupling renormalization group determination of
electron-electron scattering rate. A linear resistivity is found and its origin
lies in antiferromagnetic correlations sustained by Cooper pairing via
constructive interference. The decay of the linear resistivity term under
pressure is correlated with the strength of antiferromagnetic spin correlations
and T_c, along with an unusual build-up of the Fermi liquid scattering. The
results capture the key features of the low temperature electrical transport in
the Bechgaard salts
Organic Superconductors: when correlations and magnetism walk in
This survey provides a brief account for the start of organic
superconductivity motivated by the quest for high Tc superconductors and its
development since the eighties'. Besides superconductivity found in 1D organics
in 1980, progresses in this field of research have contributed to better
understand the physics of low dimensional conductors highlighted by the wealth
of new remarkable properties. Correlations conspire to govern the low
temperature properties of the metallic phase. The contribution of
antiferromagnetic fluctuations to the interchain Cooper pairing proposed by the
theory is borne out by experimental investigations and supports
supercondutivity emerging from a non Fermi liquid background. Quasi one
dimensional organic superconductors can therefore be considered as simple
prototype systems for the more complex high Tc materials.Comment: 41 pages, 21 figures to be published in Journal of Superconductivity
and Novel Magnetis
Chondrules – ubiquitous chondritic solids tracking the evolution of the solar protoplanetary disk
Translation initiation factors eIF4E and eIFiso4E are required for polysome formation and regulate plant growth in tobacco
Past and future evolution of nighttime urban cooling by suburban cold air drainage in Aachen
Background/aims: This study evaluated the short-term safety and feasibility of epiretinal strontium-90 brachytherapy delivered concomitantly with intravitreal bevacizumab for the treatment of subfoveal CNV due to AMD for 12 months. A 3-year follow-up is planned. Methods: In this prospective, non-randomised, multicentre study, 34 treatment-naïve patients with predominantly classic, minimally classic and occult subfoveal CNV lesions received a single treatment with 24 Gy beta radiation (strontium-90) and two injections of the anti-VEGF antibody bevacizumab. Adverse events were observed. BCVA was measured using standard ETDRS vision charts. Results: Twelve months after treatment, no radiation-associated adverse events were observed. In the intent-to-treat (ITT) population, 91% of patients lost <3 lines (15 ETDRS letters) of vision at 12 months, 68% improved or maintained their BCVA at 12 months, and 38% gained ≥3 lines. The mean change in BCVA observed at month 12 was a gain of 8.9 letters. Conclusion: The safety and efficacy of intraocular, epiretinal brachytherapy delivered concomitantly with anti-VEGF therapy for the treatment of subfoveal CNV secondary to AMD were promising in this small study population. Long-term safety will be assessed for 3 years. This regimen is being evaluated in a large, multicentre, phase III study
Twelve-month safety and visual acuity results from a feasibility study of intraocular, epiretinal radiation therapy for the treatment of subfoveal cnv secondary to amd
PURPOSE: The purpose of this study was to evaluate the short-term safety and feasibility of intraocular, epiretinal delivery of beta radiation for the treatment of subfoveal choroidal neovascularization secondary to age-related macular degeneration for 12 months. A 3-year follow-up period is planned to assess the long-term safety of the procedure. METHODS: In this nonrandomized, multicenter feasibility study, 34 treatment-naïve patients with predominantly classic, minimally classic, or occult lesions due to subfoveal choroidal neovascularization secondary to age-related macular degeneration received a single treatment with either 15 Gray (Gy) (8 patients) or 24 Gy (26 patients) beta radiation (strontium-90) using a novel intraocular delivery device. Adverse events and safety endpoints were observed and recorded. Visual acuity was measured preoperatively and postoperatively using standard Early Treatment Diabetic Retinopathy Study vision charts. RESULTS: Twelve months after treatment, no adverse events associated with exposure to radiation were observed. All patients in both 15 Gy (n = 4) and 24 Gy cohorts (n = 17) who met inclusion criteria and were treated according to protocol lost fewer than three lines of vision. Fifty percent (2/4) of the 15 Gy-treated patients and 76% (13/17) of the 24 Gy-treated patients improved or maintained their visual acuity at 12 months. In the 24 Gy group, 29% (5/17) gained three lines or more in visual acuity. The mean change in visual acuity observed at month 12 was +10.3 letters in the 24 Gy study cohort and-1.0 letters in the 15 Gy cohort. CONCLUSION: The short-term safety and efficacy of intraocular, epiretinal delivery of beta radiation for the treatment of subfoveal choroidal neovascularization was promising in this small study group and should be studied in a larger cohort of patients. Copyright © by Ophthalmic Communications Society, Inc
Digestion of raw banana starch in the small intestine of healthy humans: structural features of resistant starch
Measurement of the 24Mg(3He,p)26Al cross section: Implication for 26Al production in the early solar system
The nucleosynthetic origin of 26Al (t1/2=0.72 Myr) in the early solar system is still an open question. Several models predict that short-lived radionuclides could be produced by irradiation of circumsolar material by light charged particles emitted by the young sun. Within some models, most of the 26Al is produced by 3He-induced reactions on 24Mg. Little experimental data exist on 3He reactions so that irradiation models have had to rely on theoretical cross sections deduced from statistical nuclear reaction codes. We performed a direct measurement of the 26Al production on Mg target by means of gamma ray spectroscopy and accelerator mass spectrometry (AMS). The data indicate that the theoretical cross section used in previous approaches was overestimated by a factor of 3. Taking the particle spectra considered in theoretical approaches these data lead to a net reduction of the 26Al production of a factor of 2. We calculated the relative contribution of the different 26Al production channels depending on the irradiation scenario. We show that extremely large particles fluxes would be necessary to reach the canonical 26Al/27Al =5×10-5 in solids that were present in the early solar system. An in situ origin of this important isotopic chronometer by irradiation is unlikely
High-spin structure of the neutron-rich Ru isotopes: -vibrational bands and two-quasiparticle excitations
Matière Nucléair