Search

Two species of freshwater Parastacidae (Cherax quadricarinatus and Cherax destructor) are used for breeding in several country and to date also in Italy in one aquaculture plant located near Catania (Sicily). Although they are Australian, they seem to have some of the peculiar properties that make it important, strategic and highly appreciated species for aquaculture facilities in Italy. In fact, they mature early, have multiple reproductive cycles in a year, females can lay over a thousand eggs in a single brood and seem to tolerate wide ranges of temperature (Haubrock et al., 2021). Several authors have studied the Cherax genus from different points of view: diseases, moulting phases and the immune responses under stress conditions (Mac Loughlin et al., 2016; Sacristán et al., 2016; Foysal et al., 2020). To date, even if it is known the economic value of these species, the nutritional properties for human were not yet evaluated. The economic expenses behind the maintenance of an aquaculture facilities must certainly be justified by: i) maintenance of species that can guarantee a competitive product on the market; ii) their good nutritional levels as well as for the organoleptic characteristics. Our study, conducted as part of a project “POFEAMP 02/INA/17’ (02/INA/17, PO-FEAMP 2014-2020”, represents for the first time a preliminary evaluation of some macronutrient parameters important to know the nutritional properties of these animals. For this reason, some parameters, as the level of total protein, cholesterol, triglyceride, glucose and lactate dehydrogenase in two Cherax species, Cherax quadricarinatus and Cherax destructor were evaluated in haemolymph and in muscle tissue. These results can be useful both for evaluating the good health of these animals kept in aquaculture facilities and for evaluating better their nutritional properties. In the future, these Cherax species could increase their consumption and allow their greater presence in dietary habits.

We analyze Feynman's work on the response of an amplifier performed at Los Alamos and described in a technical report of 1946, as well as lectured on at the Cornell University in 1946-47 during his course on Mathematical Methods. The motivation for such a work was Feynman's involvement in the Manhattan Project, for which the necessity emerged of feeding the output pulses of counters into amplifiers or several other circuits, with the risk of introducing distortion at each step. In order to deal with such a problem, Feynman designed a theoretical "reference amplifier", thus enabling a characterization of the distortion by means of a benchmark relationship between phase and amplification for each frequency, and providing a standard tool for comparing the operation of real devices. A general theory was elaborated, from which he was able to deduce the basic features of an amplifier just from its response to a pulse or to a sine wave of definite frequency. Moreover, in order to apply such a theory to practical problems, a couple of remarkable examples were worked out, both for high-frequency cutoff amplifiers and for low-frequency ones. A special consideration deserves a mysteriously exceptional amplifier with best stability behavior introduced by Feynman, for which different physical interpretations are here envisaged. Feynman's earlier work then later flowed in the Hughes lectures on Mathematical Methods in Physics and Engineering of 1970-71, where he also remarked on causality properties of an amplifier, that is on certain relations between frequency and phase shift that a real amplifier has to satisfy in order not to allow output signals to appear before input ones. Quite interestingly, dispersion relations to be satisfied by the response function were introduced., 19 pages, 6 figures

We formulate a didactic proposal for introducing some fundamental concepts of quantum physics to advanced high school students, and to their teachers. The inspiration comes from some of the fundamental papers about the subject by Albert Einstein, in which many of these concepts, for example light quanta, wave-particle duality, and probability, were introduced for the first time, in a characteristically illuminating way. The proposal can be supplemented by a discussion of elementary tools of statistical physics, which are needed at some point. Preliminary results, both with students and teachers, are very promising.

We discuss a previously unpublished description of electromagnetism outlined by Richard P. Feynman in the 1960s in five handwritten pages, recently uncovered among his papers, and partly developed in later lectures. Though similar to the existing approaches deriving electromagnetism from special relativity, the present one extends a long way towards the derivation of Maxwell's equations with minimal physical assumptions. In particular, without postulating Coulomb's law, homogeneous Maxwell's equations are written down by following a route different from the standard one, i.e. first introducing electromagnetic potentials in order to write down a relativistic invariant action, which is just the inverse approach to the usual one. Also, Feynman's derivation of the Lorentz force exclusively follows from its linearity in the charge velocity and from relativistic invariance. Going further, i.e. adding the inhomogeneous Maxwell's equations, requires some more physical input, and can be done by just following conventional lines, hence this task was not pursued here. Despite its incompleteness, this way of proceeding is of great historical and epistemological significance. We also comment about its possible relevance to didactics, as an interesting supplement to usual treatments., Comment: 17 pages, no figures

Water monitoring technologies are widely used for contaminant detection in a wide variety of water ecology applications such as water treatment plants and water distribution systems. A tremendous amount of research has been conducted over the past decades to develop robust and efficient techniques of contaminant detection with minimum operating cost and energy. Recent developments in spectroscopic techniques and biosensor approach have improved the detection sensitivities, quantitatively and qualitatively. The availability of in-situ measurements and multiple detection analyses has expanded water monitoring applications in various advanced techniques including successful development in hand-held sensing devices, which improves portability in real-time basis for the detection of contaminants, such as microorganisms, pesticides, heavy metal ions, and inorganic and organic components.

A cost-effective immunosensor for the detection and isolation of dental pulp stem cells (DPSCs) based on a quartz crystal microbalance (QCM) has been developed. The recognition mechanism relies on anti-CD34 antibodies, DPSC-specific monoclonal antibodies that are anchored on the surface of the quartz crystals. Due to its high specificity, real time detection, and low cost, the proposed technology has a promising potential in the field of cell biology, for the simultaneous detection and sorting of stem cells from heterogeneous cell samples. The QCM surface was properly tailored through a biotinylated self-assembled monolayer (SAM). The biotin–avidin interaction was used to immobilize the biotinylated anti-CD34 antibody on the gold-coated quartz crystal. After antibody immobilization, a cellular pellet, with a mixed cell population, was analyzed; the results indicated that the developed QCM immunosensor is highly specific, being able to detect and sort only CD34+ cells. Our study suggests that the proposed technology can detect and efficiently sort any kind of cell from samples with high complexity, being simple, selective, and providing for more convenient and time-saving operations.

We study multi-soliton solutions of the four-dimensional SU(N) Skyrme model by combining the hedgehog ansatz for SU(N) based on the harmonic maps of $S^{2}$ into $CP^{N-1}$ and a geometrical trick which allows to analyze explicitly finite-volume effects without breaking the relevant symmetries of the ansatz. The geometric setup allows to introduce a parameter which is related to the 't Hooft coupling of a suitable large $N$ limit, in which $N\rightarrow\infty$ and the curvature of the background metric approaches zero, in such a way that their product is constant. The relevance of such a parameter to the physics of the system is pointed out. In particular, we discuss how the discrete symmetries of the configurations depend on it., 29 pages, 7 figures, minor changes, matches published version