Artificial reefs

Treball desenvolupat en el marc del programa "European Project Semester".This report is a final report of an EPS project about artificial reefs. The project is being carried out by four engineering students who are studying at Universitat Politécnica de Catalunya in Vilanova I La Geltrù. The aim of the project, which began on February 8th, is to design an artificial reef to restore the flora and fauna in a specific area near a marine observatory established by the company SARTI. The report outlines the methodology used to carry out the project during these months of work, which involved research on the existing fauna in the targeted area (fish and crustacean species), creation and analysis of 3D designs, simulation of the different models and other processes in order to create the most suitable design. The report also contains market and competitive research as well as the analysis of different materials. Overall, the report provides a detailed overview of the two models of artificial reefs that have been created to restore the marine environment.Incomin

Vitamin D deficiency as a risk factor for infection, sepsis and mortality in the critically ill: systematic review and meta-analysis

INTRODUCTION: In Europe, vitamin D deficiency is highly prevalent varying between 40% and 60% in the healthy general adult population. The consequences of vitamin D deficiency for sepsis and outcome in critically ill patients remain controversial. We therefore systematically reviewed observational cohort studies on vitamin D deficiency in the intensive care unit.METHODS: Fourteen observational reports published from January 2000 to March 2014, retrieved from Pubmed and Embase, involving 9,715 critically ill patients and serum 25-hydroxyvitamin D3 (25 (OH)-D) concentrations, were meta-analysed.RESULTS: Levels of 25 (OH)-D less than 50 nmol/L were associated with increased rates of infection (risk ratio (RR) 1.49, 95% (confidence interval (CI) 1.12 to 1.99), P = 0.007), sepsis (RR 1.46, 95% (CI 1.27 to 1.68), P <0.001), 30-day mortality (RR 1.42, 95% (CI 1.00 to 2.02), P = 0.05), and in-hospital mortality (RR 1.79, 95% (CI 1.49 to 2.16), P <0.001). In a subgroup analysis of adjusted data including vitamin D deficiency as a risk factor for 30-day mortality the pooled RR was 1.76 (95% CI 1.37 to 2.26, P <0.001).CONCLUSIONS: This meta-analysis suggests that vitamin D deficiency increases susceptibility for severe infections and mortality of the critically ill

Brown Carbon Production by Aqueous-Phase Interactions of Glyoxal and SO2

Oxalic acid and sulfate salts are major components of aerosol particles. Here, we explore the potential for their respective precursor species, glyoxal and SO2, to form atmospheric brown carbon via aqueous-phase reactions in a series of bulk aqueous and flow chamber aerosol experiments. In bulk aqueous solutions, UV- and visible-light-absorbing products are observed at pH 3–4 and 5–6, respectively, with small but detectable yields of hydroxyquinone and polyketone products formed, especially at pH 6. Hydroxymethanesulfonate (HMS), C2, and C3 sulfonates are major products detected by electrospray ionization mass spectrometry (ESI-MS) at pH 5. Past studies have assumed that the reaction of formaldehyde and sulfite was the only atmospheric source of HMS. In flow chamber experiments involving sulfite aerosol and gas-phase glyoxal with only 1 min residence times, significant aerosol growth is observed. Rapid brown carbon formation is seen with aqueous aerosol particles at \u3e80% relative humidity (RH). Brown carbon formation slows at 50–60% RH and when the aerosol particles are acidified with sulfuric acid but stops entirely only under dry conditions. This chemistry may therefore contribute to brown carbon production in cloud-processed pollution plumes as oxidizing volatile organic compounds (VOCs) interact with SO2 and water

Sustaining star formation rates in spiral galaxies - Supernova-driven turbulent accretion disk models applied to THINGS galaxies

Gas disks of spiral galaxies can be described as clumpy accretion disks without a coupling of viscosity to the actual thermal state of the gas. The model description of a turbulent disk consisting of emerging and spreading clumps (Vollmer & Beckert 2003) contains free parameters, which can be constrained by observations of molecular gas, atomic gas and the star formation rate for individual galaxies. Radial profiles of 18 nearby spiral galaxies from THINGS, HERACLES, SINGS, and GALEX data are used to compare the observed star formation efficiency, molecular fraction, and velocity dispersion to the model. The observed radially decreasing velocity dispersion can be reproduced by the model. In the framework of this model the decrease in the inner disk is due to the stellar mass distribution which dominates the gravitational potential. Introducing a radial break in the star formation efficiency into the model improves the fits significantly. This change in star formation regime is realized by replacing the free fall time in the prescription of the star formation rate with the molecule formation timescale. Depending on the star formation prescription, the break radius is located near the transition region between the molecular-gas-dominated and atomic-gas-dominated parts of the galactic disk or closer to the optical radius. It is found that only less massive galaxies (log (M (M_solar)) <~ 10) can balance gas loss via star formation by radial gas accretion within the disk. These galaxies can thus access their gas reservoirs with large angular momentum. On the other hand, the star formation of massive galaxies is determined by the external gas mass accretion rate from a putative spherical halo of ionized gas or from satellite accretion.Comment: 26 pages, 5 figures, full figures 1 and 2 as ancillary pdf files available; accepted by A

Interaction induced magnetic field asymmetry of nonlinear mesoscopic electrical transport

We demonstrate that the nonlinear I-V characteristics of a two probe conductor is not an even function of magnetic field. While the conductance of a two-probe conductor is even in magnetic field, we find that already the contributions to the current which are second order in voltage, are in general not even. This implies a departure from the Onsager microreversibility principle already in the weakly nonlinear regime. Interestingly, the effect that we find is due to the Coulomb interaction. A measurement of the magnetic field asymmetry can be used to determine the effective interaction strength. As a generic example, we discuss the I-V characteristics of a chaotic quantum dot. The ensemble averaged I-V of such a cavity is linear: nonlinearities are due to quantum interference. Consequently, phase-breaking reduces the asymmetry. We support this statement with a calculation which treats inelastic scattering with the help of a voltage probe.Comment: 45th Sanibel Symposium, submitted April 6, 200

Stress-strain curves and derived mechanical parameters of P91 steel from spherical nanoindentation at a range of temperatures

Nanoindentation allows extracting local mechanical properties out of small regions of interest, such as welds, coatings or ion-irradiated layers. Probing the surface with spherical tips combined with several data analysis procedures allows deriving the complete elastic-plastic behaviour of the material under test, from the initial elastic response during loading, to the onset of plasticity and the post-yield behaviour. This works aims at comparing different measurement and analysis protocols to spherical nanoindentation tests performed at different temperatures on a ferritic/martensitic P91 grade steel, in order to derive meaningful indentation stress−strain curves (ISSC) and estimate parameters such as indentation modulus, yield strength, work hardening exponent and ultimate tensile strength. Indentations using spherical indenters have been carried out from room temperature to 600°C in vacuum in a set-up where thermal drift has been minimised by an active surface referencing system and an accurate temperature stabilisation in the contact area. To evaluate indentation tensile properties from nanoindentation results, the determination of the contact area, the definition of representative stress and strain, and the fitting to constitutive equations are the important steps, the most adequate choice of which is still matter of discussion and may depend on the instrument, material analysed and testing procedure. In the present work it is shown that the methodology used to determine the radius of the contact is critical to achieve consistent results. The geometrical definition of the contact radius provides a consistent shape of the ISSC; however it requires a good calibration of the true indenter radius as a function of depth. On the other hand, the Hertz model for the contact radius is very sensitive to the measurement of stiffness and presumes that the elastic modulus of the material is known or derived form the initial loading. The application of the different combinations of contact radius and strain definitions to nanoindentation data obtained by multi-cycle and continuous stiffness measurements revealed that Tabor’s approach combined with geometrically determined radius best represented the ISSC relationship for the P91 characterized. This method was then extended to predict the high temperature tensile properties of the steel. The results of the nanoindentation characterization will be presented and discussed thereby comparing the performance of different measurement and analysis protocols. Please click Additional Files below to see the full abstract

Clonal analysis reveals multiple functional defects of aged murine hematopoietic stem cells

As shown using clonal assays, the mouse HSC population undergoes quantitative as well as qualitative changes with age, including lineage differentiation, HSC pool size, marrow-homing efficiency, and self-renewal