The song of the dunes as a self-synchronized instrument

Since Marco Polo (1) it has been known that some sand dunes have the peculiar ability of emitting a loud sound with a well defined frequency, sometimes for several minutes. The origin of this sustained sound has remained mysterious, partly because of its rarity in nature (2). It has been recognized that the sound is not due to the air flow around the dunes but to the motion of an avalanche (3), and not to an acoustic excitation of the grains but to their relative motion (4-7). By comparing several singing dunes and two controlled experiments, one in the laboratory and one in the field, we here demonstrate that the frequency of the sound is the frequency of the relative motion of the sand grains. The sound is produced because some moving grains synchronize their motions. The existence of a velocity threshold in both experiments further shows that this synchronization comes from an acoustic resonance within the flowing layer: if the layer is large enough it creates a resonance cavity in which grains self-synchronize.Comment: minor changes, essentially more references

A classical explanation of quantization

In the context of our recently developed emergent quantum mechanics, and, in particular, based on an assumed sub-quantum thermodynamics, the necessity of energy quantization as originally postulated by Max Planck is explained by means of purely classical physics. Moreover, under the same premises, also the energy spectrum of the quantum mechanical harmonic oscillator is derived. Essentially, Planck's constant h is shown to be indicative of a particle's "zitterbewegung" and thus of a fundamental angular momentum. The latter is identified with quantum mechanical spin, a residue of which is thus present even in the non-relativistic Schroedinger theory.Comment: 20 pages; version accepted for publication in Foundations of Physic

Enhanced Microwave Absorption Properties of Intrinsically Core/shell Structured La0.6Sr0.4MnO3Nanoparticles

The intrinsically core/shell structured La0.6Sr0.4MnO3nanoparticles with amorphous shells and ferromagnetic cores have been prepared. The magnetic, dielectric and microwave absorption properties are investigated in the frequency range from 1 to 12 GHz. An optimal reflection loss of −41.1 dB is reached at 8.2 GHz with a matching thickness of 2.2 mm, the bandwidth with a reflection loss less than −10 dB is obtained in the 5.5–11.3 GHz range for absorber thicknesses of 1.5–2.5 mm. The excellent microwave absorption properties are a consequence of the better electromagnetic matching due to the existence of the protective amorphous shells, the ferromagnetic cores, as well as the particular core/shell microstructure. As a result, the La0.6Sr0.4MnO3nanoparticles with amorphous shells and ferromagnetic cores may become attractive candidates for the new types of electromagnetic wave absorption materials

Influence of Cobalt Doping on the Physical Properties of Zn0.9Cd0.1S Nanoparticles

Zn0.9Cd0.1S nanoparticles doped with 0.005–0.24 M cobalt have been prepared by co-precipitation technique in ice bath at 280 K. For the cobalt concentration >0.18 M, XRD pattern shows unidentified phases along with Zn0.9Cd0.1S sphalerite phase. For low cobalt concentration (≤0.05 M) particle size, dXRDis ~3.5 nm, while for high cobalt concentration (>0.05 M) particle size decreases abruptly (~2 nm) as detected by XRD. However, TEM analysis shows the similar particle size (~3.5 nm) irrespective of the cobalt concentration. Local strain in the alloyed nanoparticles with cobalt concentration of 0.18 M increases ~46% in comparison to that of 0.05 M. Direct to indirect energy band-gap transition is obtained when cobalt concentration goes beyond 0.05 M. A red shift in energy band gap is also observed for both the cases. Nanoparticles with low cobalt concentrations were found to have paramagnetic nature with no antiferromagnetic coupling. A negative Curie–Weiss temperature of −75 K with antiferromagnetic coupling was obtained for the high cobalt concentration

Réflexions sur les critères d’évaluation des traitements anticancéreux lors des procédures d’autorisation de mise sur le marché

International audienc

Importance of the patient-physician interaction in assessing acceptability of HIV cure trials

International audienc

Importance of the patient-physician interaction in assessing acceptability of HIV cure trials

International audienc

Quality of life of breast cancer patients receiving high-dose-intensity chemotherapy: impact of length of cycles

International audiencehis study was designed to measure treatment side-effects and quality of life (QL) of 47 nonmetastatic breast cancer patients subjected to a dose-intensity increase while receiving a sequential high dose chemotherapy (doxorubicin+cyclophosphamide - 4 cycles). The dose-intensity increase was obtained by shortening the length of cycles from 21 to 14 days. Treatment side-effects were self-assessed in terms of frequency and associated distress in cycles 1 and 3 by using a specific side-effect self-report questionnaire (19 items). Multidimensional QL measurement was performed at inclusion and before the start of cycles 2 and 4, by using the EORTC QLQ-C30. Pain was evaluated by patients on a visual analogue scale at the same times as QL evaluation. Patients' self-ratings indicated that the total number of symptoms, the number of symptoms rated by patients as quite or very distressing, and symptom frequency were comparable whatever the length of cycle. Overall, although underestimating most patients' symptoms, physicians' reports provided similar results. However, analysis of multidimensional QL showed that, in comparison to standard administration of 4 cycles of 21 days, there was a more significant deterioration of the QLQ-C30 global QL score ( P=0.01) at the second cycle of chemotherapy and of the physical functioning score ( P=0.02) at the fourth cycle when the cycle length was reduced. This study, although limited by a small patient cohort, has shown that shortening cycles to increase dose intensity had relatively few consequences on adverse treatment effects but a highly negative impact on patients' quality of life