1,795 research outputs found
The Diophantine equation revisited
No full textLet k,l >= 2 be fixed integers, and C be an effectively computable constant depending only on k and l. In this paper, we prove that all solutions of the equation (x + 1)(k) + (x + 2)(k) + ... + (lx)(k) = y(n) in integers x, y,n with x, y >= 1, n >= 2, k not equal 3 and l 1 (mod 2) satisfy max{x, y, n} < C. The case when is even has already been completed by the second author (see [24])
On the functional codes arising from the intersections of algebraic hypersurfaces of small degree with a non-singular quadric
No full textWe discuss the functional codes C-h(Q(N)), for small h >= 3, q > 9, and for N >= 6. This continues the study of different classes of functional codes, performed on functional codes arising from quadrics and Hermitian varieties. Here, we consider the functional codes arising from the intersections of the algebraic hypersurfaces of small degree h with a given non-singular quadric Q(N) in PG(N, q)
A note on equidistant subspace codes
No full textEquidistant subspace codes are studied. A classification of the largest 1-intersecting codes in PG(5,2), whose codewords are planes, is provided. Also, new constructions of large equidistant codes are presented
The second and the third smallest arrangements of hyperplanes in finite projective spaces
No full textIn this paper we determine for some values of d the second and the third smallest configuration of hyperplanes in PG(N, q). We present links with the unique extendability of arcs in PG(2, q) and with (k, 3)-arcs having a unique trisecant
Benthic processes in fresh water fluffy sediments undergoing resuspension
No full textIn the Po river plain relict freshwater wetlands are characterised by a low free water to emergent macrophyte surface ratio, rapid infilling and fluffy sediments, undergoing frequent resuspension. Particle mixing should alter the steep gradients of dissolved gas, nutrient and organic matter quality that generally characterise sediments, with implications for benthic processes. Sediment features and solute fluxes were studied from December 2003 to February 2005 within the Busatello swamp complex (Northern Italy) by means of a combination of core incubation, porewater extraction and microprofiling. At the study site, along a 10 cm vertical profile, sediment organic matter content (32.5%), porosity (0.94) and density (1.02 g cm–3) were nearly constant. Oxygen demand measured by dark core incubation (12.7-56.9 mmol m–2 d–1) was strongly correlated with water temperature. Rates agreed reasonably well with diffusive oxygen fluxes calculated from microprofiles while ammonium and phosphorus regeneration rates predicted from porewater gradients (-309.3-43.4 and -0.1-0.7 μmol m–2 d–1, respectively) were significantly lower than rates measured via core incubations (-129.8-5420.5 and -120.4-35.4 μmol m–2 d–1, respectively). This is a probable consequence of insufficient vertical resolution of nutrient profiles and lack of steady state conditions. A sediment resuspension experiment, carried out under controlled laboratory conditions, indicated large instantaneous oxygen and nitrate consumption, a transient increase of denitrification rates and the rapid release of ammonium and soluble reactive phosphorus. In unconsolidated sediments, resuspension and mixing of sediment particles are key processes regulating mineralisation rates and benthic-pelagic coupling
Do oxic–anoxic transitions constrain organic matter mineralization in eutrophic freshwater wetlands?
No full textThis study aims at investigating decomposition processes in wetlands that are daily or seasonally exposed to intermittent oxic and anoxic conditions. We hypothesized that in wetland ecosystems where anoxia regularly establishes, decomposition rates are not affected by oxygen shortage, especially when nitrates are available. Monitoring and experiments were performed from December 2003 to January 2005 in one of the widest (81 ha) freshwater wetlands in the Po river floodplain (Natural Reserve Paludi del Busatello, Italy). Intact sediment cores were sampled on a seasonal basis. Sediment–water fluxes of oxygen, dissolved inorganic carbon, methane, and inorganic nitrogen were determined under oxic and anoxic conditions. Oxic–anoxic transitions always resulted in enhanced ammonium, dissolved inorganic carbon, and methane effluxes. At high temperatures, the methane release from sediments was inversely related to both nitrate concentrations and uptake. Likely, nitrate can compensate for the oxygen deficiency while maintaining an oxidative metabolism, either supporting microbial decomposition as an electron acceptor or stimulating the oxidation of the byproducts of the anaerobic metabolism, e.g., methane. This is a key point as the number of temperate wetlands with concurrent nitrate pollution and oxygen shortage is increasing throughout the world
La sospensione con messa alla prova: l'ambiguità come paradigma
No full textNell'ambito di un convegno dedicato alle forme, alle riforme e ai valori della giustizia penale futura, il contributo riflette sulle traiettorie d'evoluzione di uno dei più giovani moduli processuali dell'ordinamento: la sospensione con messa alla prova
The maximum and the minimum sizes of complete (n,3)-arcs inPG(2,16)
No full textIn this work we solve the packing problem for complete (n,3)-arcs in
PG(2,16), determining that the maximum size is 28 and the minimum size is 15. Both
the complete (28,3)-arc and the complete (15,3)-arc are unique up to collineations
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