Feasibility studies for light scattering experiments to determine the velocity relaxation of small particles in a fluid

An approach for measuring the non-Markoffian component in the relaxation mechanism of a Brownian particle is proposed which combines desirable features of both the shock wave experiment and conventional light scattering experiments. It is suggested that the radiation pressure generated by a C.W. laser be used to guide an individual spherical particle to terminal velocity. At an appropriate time, the beam intensity is suddenly lowered to a value at which the radiation pressure is negligible, and the ensuing velocity relaxation is measured directly

A statistical analysis of some non-linear optical effects

Statistical analysis of some nonlinear optical effects including scattering light from rotating glass and second harmonic light generated by pseudo-thermal sourc

Nuovi fasti dei magistri fontani in un frustulo epigrafico opistografo dal piccolo Aventino

Edizione di un nuovo frammento epigrafico, opistografo, rinvenuto a Roma sul piccolo Aventino e contenente liste di personaggi identificati, in base a vari indizi, con magistri Fontani

Learning from nature: Bio-Inspiration for damage-tolerant high-performance fibre-reinforced composites

Over millions of years Nature has attained highly optimized structural designs with remarkable toughness, strength, damage resistance and damage tolerance - properties that are so far difficult to combine in artificial high-performance fibre-reinforced polymers (HPFRPs). Recent studies, which have successfully replicated the structures and especially the toughening mechanisms found in flora and fauna, are reviewed in this work. At the core of the manufacturing of damage-tolerant bio-inspired composites, an understanding of the design principles and mechanisms is key. Universal and naturally-inherent design features, such as hierarchical- and organic-inorganic-structures as well as helical or fibrous arrangements of building blocks were found to promote numerous toughening mechanisms. Common to these features, the outstanding ability of diffusing damage at a sub-critical state has been identified as a powerful and effective mechanism to achieve high damage tolerance. Novel manufacturing processes suitable for HPFRP (such as tailored high-precision tape placement, micro-moulding, laser-engraving and additive manufacturing) have recently gained immense traction in the research community. This stems from the achievable and required geometrical complexity for HPFRPs and the replication of subtly balanced interaction between the material constituents. Even though trends in the literature clearly show that a bio-inspired material design philosophy is a successful strategy to design more efficient composite structures with enhanced damage tolerance and mechanical performance, Nature continues to offer new challenging opportunities yet to be explored, which could lead to a new era of HPFRP composites

Safety and commercial issues in fresh mushrooms and mushroom-based products sold at retail in Tuscany region

The compliance to European and National safety and labelling requirements relating to the sale of spontaneous and cultivated mushrooms and mushroom-based products in Tuscany was assessed. The evidence was collected by the Mycological Inspectorate of North-West Tuscany Local Health Authority during 90 inspections (from 2016 to 2020) at large-scale distribution stores, wholesalers, and restaurants in 10 cities belonging to 3 provinces, and on the labelling analysis of 98 commercial products collected at retail in 2021. Despite a substantial compliance of the inspected activities and products with the regulatory requirements, critical issues were highlighted: 1) EU legislative gap in the definition of specific measures for the safe sale of spontaneous mushrooms; 2) improper shelf storage temperatures of fresh-cut products; 3) incorrect condition of use on the labels of pre-packaged products; 4) lack of countryof-origin declaration in pre-packaged products. Furthermore, the labelling analysis highlighted that 18.4% and 15.3% of the products presented issues in the validity and correctness of the scientific names respect to national requirements in. A revision of the current EU legislation is needed to guarantee consumers safety, also considering the relevant number of poisoning cases related to false mycetisms (ingestion of edible mushrooms unproperly stored or used). Also, a specific revision and harmonization of the EU labelling of mushrooms would be desirable to protect consumers

Silica containing composite anion exchange membranes by sol–gel synthesis: a short review

This short review summarizes the literature on composite anion exchange membranes (AEM) containing an organo-silica network formed by sol-gel chemistry. The article covers AEM for diffusion dialysis (DD), for electrochemical energy technologies including fuel cells and redox flow batteries, and for electrodialysis. By applying a vast variety of organically modified silica compounds (ORMOSIL), many composite AEM reported in the last 15 years are based on poly (vinylalcohol) (PVA) or poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) used as polymer matrix. The most stringent requirements are high permselectivity and water flux for DD membranes, while high ionic conductivity is essential for electrochemical applications. Furthermore, the alkaline stability of AEM for fuel cell applications remains a challenging problem that is not yet solved. Possible future topics of investigation on composite AEM containing an organo-silica network are also discussed

Matter-wave bistability in coupled atom-molecule quantum gases

We study the matter-wave bistability in coupled atom-molecule quantum gases, in which heteronuclear molecules are created via an interspecies Feshbach resonance involving either two-species Bose or two-species Fermi atoms at zero temperature. We show that the resonant two-channel Bose model is equivalent to the nondegenerate parametric down-conversion in quantum optics, while the corresponding Fermi model can be mapped to a quantum optics model that describes a single-mode laser field interacting with an ensemble of inhomogeneously broadened two-level atoms. Using these analogy and the fact that both models are subject to the Kerr nonlinearity due to the two-body s-wave collisions, we show that under proper conditions, the population in the molecular state in both models can be made to change with the Feshbach detuning in a bistable fashion.Comment: 6 pages, 5 figure

Instability and entanglement of the ground state of the Dicke model

Using tools of quantum information theory we show that the ground state of the Dicke model exhibits an infinite sequence of instabilities (quantum-phase-like transitions). These transitions are characterized by abrupt changes of the bi-partite entanglement between atoms at critical values $\kappa_j$ of the atom-field coupling parameter $\kappa$ and are accompanied by discontinuities of the first derivative of the energy of the ground state. We show that in a weak-coupling limit ($\kappa_1\leq \kappa \leq \kappa_2$) the Coffman-Kundu-Wootters (CKW) inequalities are saturated which proves that for these values of the coupling no intrinsic multipartite entanglement (neither among the atoms nor between the atoms and the field) is generated by the atom-field interaction. We analyze also the atom-field entanglement and we show that in the strong-coupling limit the field is entangled with the atoms so that the von Neumann entropy of the atomic sample (that serves as a measure of the atom-field entanglement) takes the value $S_A={1/2}\ln (N+1)$. The entangling interaction with atoms leads to a highly sub-Poissonian photon statistics of the field mode.Comment: 4 pages, 3 figure

Fokker-Planck equation approach to optical bistability in the bad-cavity limit

In the general framework of the system size expansion of Van Kampen and Kubo, we consider the Fokker-Planck equation for a model of absorptive bistability in the bad-cavity limit. The physical system is described by the reduced atomic density operators after adiabatic elimination of the cavity field variables. Mapping of the master equation into c-number form according to the normal-ordering mapping scheme yields known results for the atomic fluctuations and correlation functions; however, it also leads to a Fokker-Planck equation with a non-positive-definite diffusion matrix. The symmetrical-order-mapping scheme eliminates this difficulty. The leading contribution to the system size expansion yields a Fokker-Planck equation for the symmetrical-ordered density function having a positive-definite diffusion matrix. The atomic expectation values and fluctuations previously derived from the quantum Langevin equations emerge naturally from this Fokker-Planck equation

Optical bistability: a self-consistent analysis of fluctuations and the spectrum of scattered light

The main purpose of this paper is to study the behavior of the atomic fluctuations and the spectrum of the light transmitted by an absorptive bistable device. To this end we develop an approximation scheme based on the so-called system-size expansion and apply it to the quantum-mechanical Langevin equations for the atomic fluctuation operators. The Bonifacio-Lugiato mean-field equations for bistability are derived from the lowest-order approximation to the system-size expansion, while the atomic correlation functions result from the next-higher-order expansion. The calculated spectrum of the transmitted light exhibits line narrowing near the bistable thresholds, discontinuous formation of sidebands along the high-transmission branch of the device, and hysteresis effects