Latest results from GRAAL collaboration

The GRAAL experimental set-up consists of a polarized and tagged photon beam that covers an energy range from a minimum of 600 MeV up to a maximum of 1500 MeV, of a liquid Hydrogen or Deuterium target and of the 4π Lagrange detector optimized for photon detection. It allows the study of pseudo-scalar and vector meson photoproduction on the nucleon in the energy range corresponding to the second and the third resonance regions. In the following, the Σ beam asymmetries in η and π~0 photoproduction on quasi-free nucleon are shown. Also single and double polarization observables in K~+A photoproduction on free proton are shown; they are important to confirm the role of new or poorly known resonances in the 1900 MeV mass region.     

The <Emphasis Type="Italic">Bild</Emphasis> Conception of Physical Theory: Helmholtz,Hertz, and Schrödinger

Hermann von Helmholtz (1821–1894) criticized the objective conception of physical theory, denying that theoretical concepts are images of physical objects. Heinrich Hertz (1857–1894) and Erwin Schrödinger (1887–1961) used the term Bild to designate their conception of physical theory, meaning an intellectual construct whose relationship to phenomena was to be analyzed. The main features of their Bild conception were an outspoken anti-inductivism and an affirmation of a partial separation of physical theory and experimental observations. Once accepted, the Bild conception loosened the bonds that still justified the attempts at the end of the nineteenth century, such Helmholtzs and Hertzs, to unify physics through a generalized form of mechanics and opened the way to the innovations of Einsteins theory of relativity.Salvo DAgostino is Professor Emeritus, Committee on the History of Science, Accademia delle Scienze detta dei Quaranta, Rome, Italy.     

Polarization observable measurements for γp → K+Λ and γp → K+Σfor energies up to 1.5 GeV

Beam asymmetries and hyperon recoil polarizations for the reactions γp → K ⁺Λ and γp → K ⁺Σ⁰ have been measured from the threshold production to 1500MeV with the GRAAL facility located at the ESRF in Grenoble. These results complement the database for the beam asymmetry, covering for the first time the production threshold region. Recent theoretical analyses are presented for which the beam asymmetry data bring interesting new information and allow to better determine some resonance parameters. Most importantly, these results strengthen the need of a new D₁₃ state around 1900MeV.     

Ultrasonic attenuation of surface acoustic waves in a thin film of superconducting Nb3Sn

The attenuation of 660 MHz surface acoustic waves propagating in a thin film of Nb₃Sn 5000 Å thick has been measured as a function of temperature from 4.2 K to 16 K. The A 15 Nb₃Sn, electron-beam codeposited on YZ lithium niobate and annealed at 700°C, was studied using 5.1 μm wavelength interdigital electrodes. The film revealed a transition temperature of 14.2 ± 0.1 K and using the BCS theory, an energy gap 2Δ(0) = 3.5 k_BT_c.     

On the Performance of Energy-Division Multiple Access with Regular Constellations

In this paper we describe a multiple-access protocol in which different users are assumed to share the same bandwidth and the same pulse. Users employ the same modulation (binary-phase shift keying, quadrature-phase shift keying, and rectangular-phase shift keying are considered) with different transmitted magnitude, and are discriminated on the basis of the corresponding magnitude at receiver location. Conditions for user discrimination are analyzed. The proposed receiver uses successive decoding in order to avoid exponential complexity of maximum-likelihood decoding. Such a scheme, compared to orthogonal multiaccess schemes (e.g. time- or frequency-division multiple access) allows to achieve larger normalized throughput for systems operating in large signal-to-noise ratio range, and may be jointly applied with classical protocols in personal-area networks. Analytical and numerical results, in terms of bit error rate and normalized throughput, are derived for performance evaluation on additive white Gaussian noise channels.     

On the Performance of Energy-Division Multiple Access Over Fading Channels

In this paper we consider a multiple-access scheme in which different users share the same bandwidth and the same pulse, and are discriminated at the receiver on the basis of the received energy using successive decoding. More specifically, we extend the performance analysis from the case of additive white Gaussian noise channels (presented in a previous work Salvo Rossi in Wirel Pers Commun, in press) to the case of fading channels. The presence of channel coefficients introduces a new degree of freedom in the transceiver design: unlike the AWGN case, different ordering among the users provides different transmitted energy, thus different overall system performance. Optimal ordering, in terms of minimum transmitted energy, is derived analytically. Analytical and numerical results, in terms of bit error rate and normalized throughput, are derived for performance evaluation in fading environments with optimal ordering exhibiting significant gains w.r.t. static ordering.     

Investigation of charge-trap memories with AlN based band engineered storage layers

This paper presents the investigation of the electrical properties of charge-trap memories with AlN based storage layers. The memory performance and reliability are studied in details and compared with the ones of a reference device using standard Si₃N₄ as storage layer. An engineered charge trapping layer is also proposed, made by an AlN/Si₃N₄ double layer, which shows reduced program/erase voltages, combined with 10⁶ excellent endurance and good retention (ΔV_T > 5 V after 10 years at 125 °C).     

Bioactive Compounds from Lemon (Citrus limon) Extract Overcome TNF-α-Induced Insulin Resistance in Cultured Adipocytes

The consumption of plant-based food is important for health promotion, especially regarding the prevention and management of chronic diseases such as diabetes. We investigated the effects of a lemon extract (LE), containing ≥20.0% total flavanones and ≥1.0% total hydroxycinnamic acids, on insulin signaling in murine 3T3-L1 adipocytes treated with TNF-α, which was used to mimic in vitro the insulin resistance condition that characterizes diabetes mellitus. Our results showed LE increased PPARγ, GLUT4 and DGAT-1 levels, demonstrating the potential of this lemon extract in the management of insulin resistance conditions associated with TNF-α pathway activation. LE treatment further decreased the release of interleukin 6 (IL-6) and restored triglyceride synthesis, which is the main feature of a healthy adipocyte.     

Preparation and characterisation of isotopically enriched Ta2O5 targets for nuclear astrophysics studies

Level energies in two-quasiparticle (2qp) structures in ¹⁵⁶ ₆₁Pm₉₅ are evaluated using the phenomenological rotor-particle model for odd-odd deformed nuclei with the inclusion of the residual p-n interaction contribution. Using these results as location guides, the experimental data from a recent ¹⁵⁶Nd decay study are used to construct a level scheme for ¹⁵⁶Pm with excitation energies upto 550 keV, wherein 26 (out of 30) ????s reported in ¹⁵⁶Nd decay are incorporated. Spin-parities and configuration assignments are suggested for 15 levels, in addition to the two isomers, in this energy domain. These investigations point to the need for information on higher-energy ????s and on ??-?? and ??-?? coincidence data from ¹⁵⁶Nd ??-decay to confirm these assignments.     

Measurement of the total photoabsorption cross section on a proton in the energy range 600–1500 MeV at the GRAAL

The total photoabsorption cross section on a free proton was measured at the GRAAL facility in the energy range E _γ = 600−1500 MeV. The large-aperture LAGRANγE detector and a liquid hydrogen target were used in the experiment performed with a back-scattered Compton gamma beam. To improve the accuracy, two alternative methods were employed. First, a subtraction method of using empty-target measurements allowed the cross section σ _tot to be evaluated directly because of a low level of the electromagnetic background. Second, an algorithm for evaluating σ _tot on the basis of summing the dominating partial cross sections was developed. Experimental results obtained for σ _tot by the two methods are compared with existing data. The article was translated by the authors. Published in Russian in Yadernaya Fizika, 2008, Vol. 71, No. 1, pp. 76–83.