Modified Newtonian Dynamics as an entropic force

Under natural assumptions on the thermodynamic properties of space and time with the holographic principle we reproduce a MOND-like behaviour of gravity on particular scales of mass and length, where Newtonian gravity requires a modification or extension if no dark matter component is introduced in the description of gravitational phenomena. The result is directly obtained with the assumption that a fundamental constant of nature with dimensions of acceleration needs to be introduced into gravitational interactions. This in turn allows for modifications or extensions of the equipartion law and/or the holographic principle. In other words, MOND-like phenomenology can be reproduced when appropriate generalised concepts at the thermodynamical level of space and/or at the holographic principle are introduced. Thermodynamical modifications are reflected in extensions to the equipartition law which occur when the temperature of the system drops below a critical value, equals to Unruh's temperature evaluated at the acceleration constant scale introduced for the description of the gravitational phenomena. Our calculations extend the ones by Verlinde (2011) in which Newtonian gravity is shown to be an emergent phenomenon, and together with it reinforces the idea that gravity at all scales is emergent.Comment: 6 pages. Accepted for publication in Journal of Modern Physics (JMP

CMOS compatible metamaterial absorbers for hyperspectral medium wave infrared imaging and sensing applications

We experimentally demonstrate a CMOS compatible medium wave infrared metal-insulator-metal (MIM) metamaterial absorber structure where for a single dielectric spacer thickness at least 93% absorption is attained for 10 separate bands centred at 3.08, 3.30, 3.53, 3.78, 4.14, 4.40, 4.72, 4.94, 5.33, 5.60 μm. Previous hyperspectral MIM metamaterial absorber designs required that the thickness of the dielectric spacer layer be adjusted in order to attain selective unity absorption across the band of interest thereby increasing complexity and cost. We show that the absorption characteristics of the hyperspectral metamaterial structures are polarization insensitive and invariant for oblique incident angles up to 25° making them suitable for practical implementation in an imaging system. Finally, we also reveal that under TM illumination and at certain oblique incident angles there is an extremely narrowband Fano resonance (Q < 50) between the MIM absorber mode and the surface plasmon polariton mode that could have applications in hazardous/toxic gas identification and biosensing

Extreme Galactic-Winds and Starburst in IR Mergers and IR QSOs

We report -as a part of a long-term study of mergers and IR QSOs- detailed spectroscopic evidences for outflow (OF) and/or Wolf Rayet features in: (i) low velocity OF in the ongoing mergers NGC 4038/39 and IRAS 23128-5919; (ii) extreme velocity OF (EVOF) in the QSOs IRAS 01003-2238 and IRAS 13218+0552; (iii) OF and EVOF in a complete sample of ultra-luminous IR galaxies/QSOs ("The IRAS 1 Jy MKO-KPNO Survey", of 118 objects). We found EVOF in IRAS 11119+3257, 14394+5332, 15130+1958 and 15462-0450. The OF components detected in these objects were mainly associated to starburst processes: i.e., to galactic-winds generated in multiple type II SN explosions and massive stars. The EVOF were detected in objects with strong starburst plus obscured IR QSOs; which suggest that interaction of both processes could generate EVOF. In addition, we analyze the presence of Wolf Rayet features in the large sample of Bright PG-QSOs (Boroson and Green 1992), and nearby mergers and galactic-wind galaxies. We found clear WR features in the Fe II QSOs (type I): PG 1244+026, 1444+407, 1448+273, 1535+547; and in the IR merger Arp 220. HST archive images of IR+BAL QSOs show in practically all of these objects "arc or shell" features probably associated to galactic-winds (i.e., to multiple type II SN explosions) and/or merger processes. Finally, we discuss the presence of extreme starburst and galactic wind as a possible evolutive link between IR merger and IR QSOs; where the relation between mergers and extreme starburst (with powerful galactic-winds) plays in important role, in the evolution of galaxies.Comment: 14 pages, 6 figure

Literature review on <i>Acacia melanoxylon</i>: its silviculture and wood

La acacia australiana (A. melanoxylon R. Br.) es una especie exótica que se ha naturalizado en el sudeste bonaerense a partir de pequeños bosquetes establecidos con fines ornamentales y de protección. Su madera es valiosa y muy apreciada tanto en su región de origen (Australia continental e isla de Tasmania), donde existe una industria dependiente de ella, como en Sudáfrica, Nueva Zelanda y más recientemente, Brasil y Chile, donde es una exótica con comportamiento y rendimientos satisfactorios bajo una apropiada ordenación forestal. El presente trabajo resume aspectos de su particular e intensiva silvicultura, como podas, raleos, especies protectoras o acompañantes y manejo de la luz con el fin obtener fustes rectos, largos y sin nudos tanto en monte nativo como en plantaciones. También se enuncian los datos volumétricos y de crecimiento para diferentes sitios. Finalmente, se caracteriza su madera, que constituiría una importante materia prima alternativa y disponible en las regiones de Balcarce y Azul, frente a las Mirtáceas, Pináceas y Salicáceas que tradicionalmente han sido utilizadas en los emprendimientos forestales.Blackwood (A. melanoxylon R. Br.) is an exotic turned into a naturalised species in the south-eastern region of the province of Buenos Aires originating from afforestations of small scale established with ornamental and shelter purposes. It is a highly valued timber species in its original region (continental Australia and Tasmania) where the industry has developed depending on it. In South Africa, New Zealand, and more recently, Brazil and Chile, it thrives as an exotic with satisfactory behaviour and performance under the appropriate forest management. The present work summarises aspects of its particular intensive silviculture as form pruning, thinning, nurse crops and light management aiming to obtain acceptable sawlogs and knot-free timber in the native forest as well as in plantations. Volume and growth data from different site conditions are also discussed. Finally, its wood is characterised as an important raw material available in the regions of Balcarce and Azul and an alternative wood to that coming from Mirtaceae, Pinaceae and Salicaceae traditionally used by forest enterprises.Facultad de Ciencias Agrarias y Forestale