Post-fire residual mechanical properties of concrete made with recycled concrete coarse aggregates

This paper presents results of an experimental study on the residual mechanical performance of concrete produced with recycled coarse aggregates, after being subjected to high temperatures. Four different concrete compositions were prepared: a reference concrete made with natural coarse aggregates and three concrete mixes with replacement rates of 20%, 50% and 100% of natural coarse aggregates by recycled concrete coarse aggregates. Specimens were exposed for a period of 1 h to temperatures of 400 °C, 600 °C and 800 °C, after being heated in accordance with ISO 834 time–temperature curve. After cooling down to ambient temperature, the following basic mechanical properties were then evaluated and compared with reference values obtained prior to thermal exposure: (i) compressive strength; (ii) tensile splitting strength; and (iii) elasticity modulus. Results obtained show that there are no significant differences in the thermal response and post-fire mechanical behaviour of concrete made with recycled coarse aggregates, when compared to conventional concrete.     

Modeling of the Extraction Equilibrium of Copper from Sulfate Solutions with Acorga M5640

The extraction equilibrium of copper from sulfate media with the aldoxime Acorga M5640 in ShellSol D70 has been investigated. The distribution results were interpreted by taking into account the nonideality of the aqueous phase. The activity of copper and hydrogen ions in the target systems CuSO₄/H₂SO₄/Na₂SO₄ and CuSO₄/H₂SO₄/Fe₂(SO₄)₃/ZnSO₄ were calculated through the speciation of the aqueous solutions and by applying the Pitzer model. The experimental pH values were found in good agreement with the predicted pH values. A model considering the dimerization of the aldoxime extractant was proposed to predict the distribution ratio and the copper loading isotherms. The extraction constant at infinite dilution and the apparent dimerization constant were evaluated from the experimental data and were found to be 10^{3.06 ± 0.07} and 51 ± 9 M^?1, respectively, at 25°C.     

A game-based algorithm for fair bandwidth allocation in Fibre-Wireless access networks

Fibre-Wireless (FiWi) access networks have been proposed as flexible and cost-effective solutions for future access networks. At the wireless mesh section, wireless routers have to forward both local traffic from directly connected users and foreign traffic from neighbour wireless routers. How to allocate resources to local and foreign traffic at each router in a balanced way, while avoiding starvation of routers requiring less resources, is a fundamental issue that must be solved so that new services emerge. Here, we develop a repeated game framework for bandwidth allocation and propose an algorithm that allocates bandwidth in a fair manner. The algorithm is able to detect over claiming routers and avoid possible denial of service that these may cause to others. Moreover, unfruitful use of resource is prevented, avoiding the forwarding of packets that would be dropped at some point later in the path, and queueing delay conditions are kept similar among local and foreign traffic. These fair network conditions open way for QoS support since it is easier to ensure the operationality of services.     

Human dermal exposure to galaxolide from personal care products

Musks are synthetic fragrances applied on personal care and household products as fixatives, by retarding the release of other fragrances with higher volatility. Galaxolide is the most used polycyclic musk since the 90th decade, and it has been detected in several environmental and biological matrices, particularly in human tissues and fluids. For exposure assessment purposes, large‐monitoring data need to be obtained and rapid but reliable analytical techniques are requested. The main objective of this study is to develop and validate a new and fast analytical methodology to quantify galaxolide in personal care products and to apply this method to real matrices like skin care products (creams and lotions), shower products (soap bar), hair care products (shampoo and hair conditioner) and oral care products (toothpaste), to evaluate the human dermal exposure risk. A dispersive solid‐phase extraction is proposed, using QuEChERS methodology, followed by HPLC with fluorescence detection. Some extraction parameters were studied, like the ratio of sample/solvent amounts, the homogenization time, the salt addition effect and the used sorbents. The validation parameters of the developed method were the following: a linearity range of 0.005–1.002 mg kg^?1 sample, a limit of detection of 0.001 mg kg^?1 sample, repeatability between 0.7% and 11.3% (variation coefficient of six standard injections), an intermediate precision of 2.5% (variation coefficient of six independent analysis of the same sample), mean recoveries ranging from 65% (soap bar) to 95% (body cream) and 3% of global uncertainty in most of the working range. The time of analysis, including the extraction steps, is 60 min, allowing a throughput of 4 samples h^?1. Galaxolide was detected in all of the seven analysed products in concentrations ranging from 0.04 ± 0.01 mg kg^?1 sample (toothpaste) to 280.78 ± 8.19 mg kg^?1 sample (perfumed body cream), which may correspond to a significant estimated daily human dermal exposure of 904 μg day^?1.     

The effect of starch isolation method on physical and functional properties of Portuguese nut starches. II. Q. rotundifolia Lam. and Q. suber Lam. acorns starches

A new starch was isolated from fruits of two acorn species, Quercus rotundifolia and Quercus suber by alkaline (A3S) and enzymatic (ENZ) methods and physical and functional properties were studied. The isolation method induced changes in most of those properties in the isolated starches, mainly in resistant starch content, syneresis, pasting, thermal and rheological properties. Isolated acorn starches presented high amylose content (53–59%) and resistant starch content (30.8–41.4%). Acorn starches showed limited and similar solubility values and swelling power values, showing a gradual increase from 60 °C to 90 °C. The pasting temperatures ranged from 67.5 to 72.0 °C and pastes did not present breakdown, which is suggestive of a high paste stability of acorn starches during heating. At ambient temperature the turbidity and syneresis values were low, but when held at freezing temperatures the syneresis significantly increased. Thermal analysis revealed that the acorn starches easily undergo transition phenomena as shown by the low T_o and enthalpy values (4.1–4.3 J/g), these effects were more evident in starches isolated by ENZ method. Pastes are more elastic than viscous and form strong gels after cooling. Q. suber starch was shown to be more sensitive to the effect of isolation method. Generally, starch isolated by enzymatic method presented less interesting functional properties, since this isolation procedure greater affected the raw structure of starches.     

Copper(I)/N‐Heterocyclic Carbene (NHC)‐Catalyzed Addition of Terminal Alkynes to Trifluoromethyl Ketones for Use in Continuous Reactors

A copper(I)/N‐heterocyclic carbene complex‐catalyzed addition of terminal alkynes to trifluoromethyl ketones at low loading is described. The developed process functions well using a range of terminal alkynes but functions best when an aryl trifluoromethyl ketone is used. This substrate scope is well‐suited for the production of active pharmaceutical ingredients (APIs) such as efavirenz. In this vein, we demonstrate that the described method can be translated into a flow process laying the framework for a completely continuous synthesis of efavirenz in the future.

     

Alcohol use by undergraduate students on their 21st birthday: Predictors of actual consumption, anticipated consumption, and normative beliefs.

Recent research has identified celebration of a 21st birthday as an environmental event during which many college students engage in risky levels of alcohol consumption. The current study examined the relationship between personality and different aspects of alcohol use during 21st birthday celebrations: actual amount consumed for those who had turned 21, anticipated amount consumed for those under the age of 21, and normative beliefs regarding the amount other students consume on their 21st birthdays. Sensation seeking and impulsivity both displayed significant bivariate relationships with all three aspects of 21st birthday drinking. Personality traits did not contribute unique variance to actual 21st birthday drinking after the effects of typical alcohol consumption were accounted for in the models. Impulsivity contributed unique variance to models accounting for anticipated drinking and normative beliefs. Additional research is necessary to better understand the role personality variables play on alcohol consumption during 21st birthday celebrations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Atomic layer deposition of tantalum nitride based thin films from cyclopentadienyl type precursor

Tantalum nitride based thin films have been deposited on p-Si (100) and SiO₂/Si by thermal Atomic Layer Deposition (ALD) using either the Ta(= N^tBu)(NEt₂)₃ or a derivative, in which one dialkylamido ligand is substituted by a η⁵-cyclopentadienyl (η⁵-Cp), as metal organic precursors with ammonia as reducing agent. TaN_xC_y self-limiting temperature dependent ALD growth was achieved for the TaCp(= N^tBu)(NEt₂)₂/NH₃ process with a growth rate of 0.51-0.91 Å cycle⁻¹ in the 400-425 °C temperature range while between 240 and 280 °C, the growth of TaN based films from the Ta(= N^tBu)(NEt₂)₃ was accompanied by a partial decomposition of the precursor. The η⁵-cyclopentadienyl type compound allows lower nitrogen content in the precursor and thereafter in the deposited film. Although N/Ta ratio is close to one at temperatures of 390 and 400 °C, as analyzed by Rutherford Back Scattering and Nuclear Reaction Analysis, films were amorphous independently of the deposition temperature. Since Ta-C bonds are present in the Cp derivative, the TaCp(= N^tBu)(NEt₂)₂ tends more likely to form tantalum carbide compared to Ta(= N^tBu)(NEt₂)₃, which leads to lower thin film resistivity. For both precursors, employed in their respective ALD window, films were smooth with a root-mean-square roughness close to 1 nm.     

A propagation model for urban microcellular systems at the UHF band

This paper presents a new propagation model for urban environments, which takes into account propagation over buildings and inside streets. The formulation for multiple diffraction loss over rooftops results from a combination of the Vogler (1982) and Xia and Bertoni (1992) models, which enables its application to profiles of buildings with nonuniform heights and spacings, keeping the calculation time low. A ray-tracing tool based on the image method and on the uniform theory of diffraction (UTD) has been developed to estimate the attenuation inside streets; loss introduced by vegetation is also accounted for. The results obtained with the application of the model to two areas of Lisbon show the importance of rays conducted by transversal streets and diffracted by vertical edges when predicting the signal near crossroads. Average values of 3.5 dB, -0.07 dB, and 2.6 dB were obtained for the mean absolute and relative errors and for the standard deviation error, respectively     

A CMOS optical microspectrometer with light-to-frequency converter,bus interface, and stray-light compensation

A single-chip CMOS optical microspectrometer containing an array of 16 addressable Fabry-Perot (F-P) etalons (each one with different resonance cavity length), photodetectors, and circuits for readout, multiplexing, and driving a serial bus interface has been fabricated in a standard 1.6-μm CMOS technology (chip area 3.9 × 4.2 mm² ). The result is a chip that can operate using only four external connections (including V_dd and V_ss) covering the optical range of 380-500 nm with FNVHM = 18 nm. Frequency output and serial bus interface allow easy multisensor, multichip interfacing using a microcontroller or a personal computer. Also, stray-light compensation techniques are implemented. Power consumption is 1250 μW at a clock frequency of 1 MHz