Laser Shock Microformingof Thin Metal Sheets with ns Lasers

Continuous and long-pulse lasers have been used for the forming of metal sheets in macroscopic mechanical applications. However, for the manufacturing of micro-electromechanical systems (MEMS), the use of ns laser pulses provides a suitable parameter matching over an important range of sheet components that, preserving the short interaction time scale required for the predominantly mechanical (shock) induction of deformation residual stresses, allows for the successful processing of components in a medium range of miniaturization without appreciable thermal deformation.. In the present paper, the physics of laser shock microforming and the influence of the different experimental parameters on the net bending angle are presented

Assessment of the methane emission for different typologies of fattening swine facilities in the department of Antioquia – Colombia

The explosive growth of swine production at high stocking densities in confinement farming worldwide, has raised concerns the environmental impact, health and livestock productivity and the production of associated gases in this type of large-scale farms. The aim of this paper was to study the methane gas concentration and emissions of ten different typologies of swine production installations. The facilities were in the department of Antioquia - Colombia, they were located between 800–2,300 meters above sea level (m.a.s.l.) of heights, they mainly employed natural ventilation as refrigeration strategy and they were used for pigs in fattening stage. Methane measurements were taken at animal height. Sensors were located at intermediate points of the ventilation inlet and outlet areas. The behaviour of methane concentration and emission of the facilities were analysed along with the correlation and temporal evolution of climatic variables, comfort indices and construction typologies. The information was analysed using descriptive statistics, analysis of variance (ANOVA) and principal component analysis (PCA). Were found an average of CH4 Emission Rate (ER) per facility (kg year-1 ) of 607.9, Global Warming Potential (GWP) per facility (kg year-1 ) of 15,197.42 and significant correlations between ER and cleaning frequency (CF), animal unit (AU), air flow (Q), animal density(AD) and relative humidity (RH) were evidenced. This is the first research reported in Colombia, that will be important to create some governmental policies

Impact of terrestrial mining and intensive agriculture in pollution of estuarine surface sediments: Spatial distribution of trace metals in the Gulf of Uraba, Colombia

The Gulf of Uraba (northwestern Colombia) is a geostrategic region, rich in biodiversity and natural resources. Its economy is mainly based on agribusinesses and mining activities. In this research is determined the impact of these activities in bottom surface sediments of the estuary. Thus, grain size, total organic carbon, total nitrogen, carbonates, Ag, Al, Ca, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb and Zn concentrations from 17 surface sediment samples were obtained and enrichment factors (EF) as well as geo-accumulation indices (Igeo) were calculated to determine the contamination level in the gulf. EF and Igeo values revealed that the estuary is extremely contaminated with Ag and moderately contaminated with Zn. Therefore, the observed enrichment of Ag may be explained as a residue of the extraction of gold and platinum-group metals and the enrichment with Zn associated mainly to pesticides used in banana plantations. (C) 2016 Elsevier Ltd. All rights reserved

Exudados radicales de alfalfa (Medicago sativa L.) en condiciones de estrés salino. Expresión de genes nod en Rhizobium

El estrés salino puede interferir con la transcripción de los genes de nodulación(nod) en Rhizobium al modificar la composición de exudados radicales o la respuesta de rizobia. Exudados de raíces de alfalfa (Medicago sativa L .) crecidas en NaCI 0 ,5 % fueron colectados durante 6 días y analizados por TLC. La inducción de la transcripción de los genes nod de rizobia se realizó mediante el empleo de un vector de expresión con la fusión nod-lacZ. Los resultados indican que los perfiles de exudados de las plantas tratadas difieren en tiempo con los controles , y que este retardo inducido por la concentración salina no afecta la capacidad inductora de los genes nod

Estudios In Vitro de Cementos de α-Fosfato Tricálcico Modificados con β-Silicato Dicálcico

The combination of in situ self-setting and biocompatibility, makes calcium phosphate cements highly promising materials for a wide range of clinical applications. However, its low strength limits their use only to lowstress applications. β-Dicalcium silicate (β-C2S) is a Portland cement component, able to react with water to form a hydrated phase that enhance mechanical strength of material. Different authors reported the bioactive capacity of this compound. In this investigation, α-TCP cements modified with β-C2S were prepared. The α-tricalcium phosphate (αTCP) powder was prepared through acid-base method, and β-C2S was synthesized by sol-gel method. Materials were characterized both chemically and physically. Biodegradability was studied by soaking the materials in simulated body fluid for various time periods. The results showed that a cement with 20 % of β-C2S exhibited greater compressive strength and pH values (19,8 MPa and 8,09 respectively).La capacidad que presentan los cementos de fosfato de calcio de fraguar en condiciones fisiológicas, así como su excelente biocompatibilidad, hacen estos materiales factibles para diferentes aplicaciones clínicas. Sin embargo sus bajas propiedades mecánicas limitan dichas aplicaciones a zonas de menores esfuerzos físicos. El βsilicato dicálcico (β-C2S) es un componente del cemento Portland, que reacciona con agua formando una fase hidratada de elevada resistencia mecánica. Diferentes autores han demostrado la capacidad bioactiva de este compuesto. En el presente trabajo fueron preparados cementos de α-fosfato tricálcico (α-TCP) modificados con β-C2S.El polvo de α-TCP fue obtenido por reacción ácido-base y el β-C2S vía sol-gel. Los materiales fueron caracterizados físico-químicamente, además de estudiar la biodegradación de los mismos a través de su inmersión en solución fisiológica simulada. Los mayores valores de resistencia a la compresión y pH correspondieron al cemento con 20% de β-C2S (19,8 MPa and 8,09 respectivamente

Comments on the Boundary Scattering Phase

We present a simple solution to the crossing equation for an open string worldsheet reflection matrix, with boundaries preserving a SU(1|2)^2 residual symmetry, which constrains the boundary dressing factor. In addition, we also propose an analogous crossing equation for the dressing factor where extra boundary degrees of freedom preserve a SU(2|2)^2 residual symmetry.Comment: 14 pages, 2 figures; v2: affiliation correcte

Giant Gravitons - with Strings Attached (III)

We develop techniques to compute the one-loop anomalous dimensions of operators in the ${\cal N}=4$ super Yang-Mills theory that are dual to open strings ending on boundstates of sphere giant gravitons. Our results, which are applicable to excitations involving an arbitrary number of open strings, generalize the single string results of hep-th/0701067. The open strings we consider carry angular momentum on an S$^3$ embedded in the S$^5$ of the AdS$_5\times$S$^5$ background. The problem of computing the one loop anomalous dimensions is replaced with the problem of diagonalizing an interacting Cuntz oscillator Hamiltonian. Our Cuntz oscillator dynamics illustrates how the Chan-Paton factors for open strings propagating on multiple branes can arise dynamically.Comment: 66 pages; v2: improved presentatio

A study of open strings ending on giant gravitons, spin chains and integrability

We systematically study the spectrum of open strings attached to half BPS giant gravitons in the N=4 SYM AdS/CFT setup. We find that some null trajectories along the giant graviton are actually null geodesics of AdS_5x S^5, so that we can study the problem in a plane wave limit setup. We also find the description of these states at weak 't Hooft coupling in the dual CFT. We show how the dual description is given by an open spin chain with variable number of sites. We analyze this system in detail and find numerical evidence for integrability. We also discover an interesting instability of long open strings in Ramond-Ramond backgrounds that is characterized by having a continuum spectrum of the string, which is separated from the ground state by a gap. This instability arises from accelerating the D-brane on which the strings end via the Ramond-Ramond field. From the integrable spin chain point of view, this instability prevents us from formulating the integrable structure in terms of a Bethe Ansatz construction.Comment: 38 pages+appendices, 9 figures. Uses JHEP3. v2: added reference

Bound State Transfer Matrix for AdS5 x S5 Superstring

We apply the algebraic Bethe ansatz technique to compute the eigenvalues of the transfer matrix constructed from the general bound state S-matrix of the light-cone AdS5 x S5 superstring. This allows us to verify certain conjectures on the quantum characteristic function, and to extend them to the general case.Comment: 36 pages, LaTeX, v2: typos corrected, ref added; v3: accepted for publication in JHEP