Interactions suppress quasiparticle tunneling at Hall bar constrictions

Tunneling of fractionally charged quasiparticles across a two-dimensional electron system on a fractional quantum Hall plateau is expected to be strongly enhanced at low temperatures. This theoretical prediction is at odds with recent experimental studies of samples with weakly pinched quantum-point-contact constrictions in which the opposite behavior is observed. We argue here that this unexpected finding is a consequence of electron-electron interactions near the point contact.     

Electromagnetic fields in magnetic materials: A resource letter

This work is a collection of selected, significant references focussing upon magnetic materials and their interaction with electromagnetic fields. The major topics included are ferrites, plasmas (both atmospheric and laboratory), magnetic composites, magnetic dielectric fluids, ferroelectric liquid crystals. Sections discussing general magnetic materials and phenomena are also included.     

Theoretical analysis of the performance of a gravity-controlled solar concentrator

Summary We here analyse the geometrical concentrations and the energy gathered by the fixed collector of a solar concentrator, whose curvature is determined by the force of gravity and by a distribution of varable density. These quantities are directly compared with those of concentrators controlled merely by gravity, that is the curvature of which s determined only by the force of gravity. A more realistic analysis than one would have from the energy presumably gathered by the collector during the ten years from 1964 to 1973 is achieved, by utilizing the data on solar radiation collected at the Geophysical and Geodetical Institute of Genoa University in the city of Genoa (44^o 24′ 53″ N latitude, 55 m above sea-level).

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Riassunto Si analizzano le concentrazioni geometriche e l'energia raccolta dal collettore fisso di un concentratore solare, con curvatura determinata dalla forza di gravità e da una distribuzione di densità variabile, confrontandole direttamente con quelle di concentratori puramente gravitazionali, con curvatura determinata cioè dalla sola forza di gravità. Un'analisi più realistica di quella che presumibilmente sarebbe stata l'energia raccolta dal collettore nei dieci anni, dal 1964 al 1973, è fatta utilizzando i dati di insolazione rilevati dall'Istituto Geofisico e Geodetico dell'Università di Genova presso la città di Genova (44^o 24′ 53″ latitudine nord, quota 55 metri sul livello del mare).

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Резюме В этой работе мы анализируем геометрические концентрации и энергию, собранную фиксированным коллектором солнечного концентратора, кривизна которого определяетяется силой гравитации и распределением переменной плотности. Полученные результаты непосредственно сравниваются с результатами для концентраторов, контролируемемых только гравитацией, т.е. кривизна которых определяется только силой травитации. Выполняется более реалистческий анализ, чем анализ, проведенный ранее, собранной энергии коллектором в течение десяти лет с 1964 по 1973 годы. При анализе использовались данные по солнечной радиации, собранные Геофизическим иГеодезическим Институтом Университета Генуи (44^o 24′ 53″ северной широты, 55 метров вьше уровня моря).

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A study completed within the Finalized Energy Program of C.N.R.

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About to graduate at the Istituto di Scienze Fisiche of the Genoa University.     

Application of the Courant-Isaacson-Rees method to solve the shallow-water hydrodynamic equations

A finite-difference scheme is presented to solve the shallow-water hydrodynamic equations which describe the behavior of natural water bodies under the influence of wind stress, atmospheric pressure gradients, and tides. The numerical technique, which is an extension of the two-dimensional method of Courant, Isaacson, and Rees (1952), proved to be accurate and computationally stable for two-dimensional oceanographic investigations. Numerical simulations are given for wind-driven circulation in the Ligurian Sea.     

Neue Substitutions-Verbindungen des K3[Cr(NCS)6] mit tertiären Phosphinen

New Substitution Compounds of K₃[Cr(NCS)₆] with Tertiary Phosphines . New substitution reactions of K₃[Cr(NCS)₆] with mixed tertiary phophines in n-butanol were carried out. The formulae of the new anions: [Cr(NCS)₄(diethyl-phenylphosphine)₂]^? and [Cr(NCS)₄(diethyl-p-tolyl-phosphine)₂]^? were established by preparation of 30 new derivatives with the hydrochlorides of some organic N-bases, metals, and metal(III) ammines. Electronic and i.r. spectral data are communicated.     

An unsteady state method for the measurement of polymer thermal diffusivity: I. Development of a cell

In this work the development of a cell able to determine the thermal diffusivity of polymers in their fused or solid state, using an unsteady state technique, is presented. In this case a step down perturbation method was used because of its easy experimental setup. For each experimental run a temperature step down perturbation of 10 °C was applied, and the temperature evolution with time and position were registered and saved. Thermal diffusivities were then determined by regression using those data and a simple analytical model. The polymers used to test the cell were high density polyethylene and polypropylene (PP). For the first polymer, the thermal diffusivity was found to be 2.05×10⁻⁷ m²/s, which compare satisfactorily with a value of 1.97×10⁻⁷ m²/s calculated from reported values of density, heat capacity and heat conductivity. For the PP the value was found to be 7.08×10⁻⁷ m²/s with a positive deviation of 5.05% when compared with a computed value of 6.74×10⁻⁷ m²/s. Taking into account experimental errors, and the natural variations between different stocks of materials, the observed differences are acceptable.