An electrically compensated radiometer

The radiometer described applies electronic feedback to dynamically balance the radiant power absorbed by a radiation absorbing sensor through an equivalent electric joule heating of a compensating sensor shielded from incident radiation. The instrument combines simple construction and the small time constant achieved in thermocouple detectors with the self-calibration and large output signal characteristic of resistance thermometer instruments. Theoretical instrument response equations indicate that, for perfect compensation, with identical sensor geometries, orientations and materials, output is independent of ambient temperature or sensor inclination. Measurement stability is determined principally by feedback amplifier drift. Initial measurements on a simple model pyranometer confirm the validity of the concept. For 3500 readings with radiant flux in the range of 100 to 800 W/m² and incidence within about 40° from the vertical, the standard deviation of the model was 0.4% and the linear correlation coefficient 0.988 with respect to an Eppley PSP pyranometer. Threshold radiant flux was about 100 ± 8 mW/m² and the expected uncertainty at a radiant flux of 1 kW/m² about 2 W/m². The time constant, for 20 μm tungsten wire sensors was of the order of 45 ms.     

Spectrokinetic Analysis of the NOx Storage Over a Pt–Ba/Al2O3 Lean NOx Trap Catalyst

In this work the kinetics of the (reactive) lean accumulation phase of the NO_x storage-reduction process is described through a detailed kinetic model, involving both the gas-phase molecules and the adsorbed species. Kinetic data have been collected following a novel approach based on simultaneous operando spectroscopic measurements and on-line pulse reactor effluent analysis. To our knowledge, this is the first time the temporal evolutions of the concentration of both the surface and the gas species are used jointly to describe the kinetic of a transient catalytic process.     

Gelatine/PLLA sponge-like scaffolds: morphological and biological characterization

Biodegradable synthetic polymers such as poly(lactic acid) (PLA) are widely used to prepare scaffolds for cell transplantation and tissue growth, using different techniques set up for the purpose. However the poor hydrophilicity of these polymers represents the main limitation to their use as scaffolds because it causes a low affinity for the cells. An effective way to solve this problem could be represented by the addition of biopolymers that are in general highly hydrophilic. The present work concerns porous biodegradable sponge-like systems based on poly(l-lactic acid) (PLLA) and gelatine. Morphology and porosity characteristics of the sponges were studied by scanning electron microscopy and mercury intrusion porosimetry respectively. Blood compatibility was investigated by bovine plasma fibrinogen (BPF) adsorption test and platelet adhesion test (PAT). The cell culture method was used in order to evaluate the ability of the matrices to work as scaffolds for tissue regeneration. The obtained results indicate that the sponges have interesting porous characteristics, good blood compatibility and above all good ability to support cell adhesion and growth. In fact viable and metabolically active animal cells were found inside the sponges after 8 weeks in culture. On this basis the systems produced seem to be good candidates as scaffolds for tissue regeneration.     

Detailed Kinetics of the Fischer�CTropsch Synthesis on Cobalt Catalysts Based on H-Assisted CO Activation

A complete mechanistic kinetic model of the Fischer?CTropsch synthesis (FTS) over a Co/Al₂O₃ state-of-the-art catalyst is developed here under conditions relevant to industrial operation. On the basis of the most recent findings on the reaction mechanism, here described according to the H-assisted CO dissociation theory and the alkyl chain growth mechanism, and on the basis of the latest indications available on the rate determining step involved in the CO activation process, rate expressions for all the steps leading to CO and H₂ consumption and n-paraffins, ??-olefins and H₂O formation are derived. Such expressions are functions of the molar fraction of CO, H₂ and olefins in the liquid phase surrounding the catalyst pellets, that in turn are related to the gas-phase pressure and composition, and of the surface coverage of the adsorbed species. Thermodynamic and kinetic parameters involved in the model are estimated by non-linear multi-response regression on a complete set of FTS experimental data collected in a lab-scale tubular reactor at steady-state conditions (P = 8?C25 bar, T = 210?C235 °C, H₂/CO feed ratio = 1.8?C2.7 mol mol^?1, GHSV = 2,000?C7,000 cm³(STP) h^?1 g _cat ^?1 ). Both the experimental CO conversion and the hydrocarbon distribution (up to N = 50) in FTS are well predicted by the model with 13 adaptive parameters, without the need of introducing any empirical parameter. Analysis of the model offers insight in the rates of the elementary steps associated with the reaction mechanism and in the surface coverages of the adsorbed species. Such information explains the peculiar reactivity observed over cobalt-based Fischer?CTropsch catalysts, and can provide guidelines for the design of more active and selective catalytic materials.     

Analysis of design variables for water-gas-shift reactors by model-based optimization

This work analyzes the water-gas-shift reactor design as component of the CO clean-up system of the ethanol processor for H₂ production applied to PEM fuel cells. The WGS reactor constitutes the element of greater volume of the processor motivating its optimization. A model-based reactor optimization for different reactor configurations permits to obtain both designs for reducing volumes and optimal operating conditions. The heterogeneous model used allows computing the optimal reactor length and diameter, and the optimal catalyst particle diameter. The model computes the constraints required for catalyst, such as maximum and minimum operation temperature. The volume is sensitive to the CO outlet concentration. According to the required CO conversion it is necessary more than one reactor unit for the case study analyzed. When considering the insulating material, there exists an optimal thickness that affects the final volume and the design variables. These results are useful for estimating the minimum and relative sizes that allows conventional reactor technology.     

Biochemical composition of two red seaweed species grown on the Brazilian coast

BACKGROUND: Algae species have been used as an important source of food because they are highly nutritive considering their vitamin, protein, mineral, fiber, essential fatty acid and carbohydrate contents. However, a large number of seaweeds have been poorly studied, especially Brazilian species. Two red macroalgae species from the Brazilian coast (Plocamium brasiliense and Ochtodes secundiramea) were assessed with respect to their total lipid, fatty acid, total nitrogen, protein, amino acid and total carbohydrate contents. RESULTS: The total lipid contents (dry weight) were 36.3 and 35.4 g kg^?1; fatty acid contents were 9.3 and 12.1 g kg^?1; total nitrogen contents were 37.4 and 24.9 g kg^?1; protein contents were 157.2 and 101.0 g kg^?1; amino acid contents were 127.5 and 91.4 g kg^?1; and total carbohydrate contents were 520.3 and 450.7 g kg^?1 for P. brasiliense and O. secundiramea, respectively. CONCLUSION: Considering these compositions, both algae species were determined to have sources of protein, essential amino acids and carbohydrates similar to the edible seaweeds Laminaria japonica and Palmaria palmata. Copyright © 2011 Society of Chemical Industry     

Supported Faceted Gold Nanoparticles with Tunable Surface Plasmon Resonance for NIR‐SERS

A novel dry plasma methodology for fabricating directly stabilized substrate‐supported gold nanoparticle (NP) ensembles for near infrared surface enhanced Raman scattering (NIR SERS) is presented. This maskless stepwise growth exploits Au‐sulfide seeds by plasma sulfidization of gold nuclei to produce highly faceted Au NPs with a multiple plasmon resonance that can be tuned from the visible to the near infrared, down to 1400 nm. The role of Au sulfidization in modifying the dynamics of Au NPs and of the corresponding plasmon resonance is discussed. The tunability of the plasmon resonance in a broad range is shown and the effectiveness as substrates for NIR SERS is demonstrated. The SERS response is investigated by using different laser sources operating both in the visible and in the NIR. SERS mapping of the SERS enhancement factor is carried out in order to evaluate their effectiveness, stability, and reproducibility as NIR SERS substrates, also in comparison with gold NPs fabricated by conventional sputtering and with the state‐of‐the‐art in the current literature.     

Performance assessment of drop tube reactor for biomass fast pyrolysis using process simulator

Biomass pyrolysis process from a drop tube reactor was modelled in a plug flow reactor using Aspen Plus process simulation software. A kinetic mechanism for pyrolysis was developed considering the recent improvements and updated kinetic schemes to account for different content of cellulose, hemicellulose, and lignin. In this regard, oak, beechwood, rice straw, and cassava stalk biomasses were analyzed. The main phenomena governing the pyrolysis process are identified in terms of the characteristic times. Pyrolysis process was found to be reaction rate controlled. Effects of pyrolysis temperature on bio-oil, gases, and char yields were evaluated. At optimum pyrolysis conditions (i.e., 500°C), a bio-oil yield of 67.3, 64, 43, and 52 wt.% were obtained from oak, beechwood, rice straw, and cassava stalk, respectively. Oak and beechwood were found to give high yields of bio-oil, while rice straw produced high gas and char yields compared to other biomasses. Although temperature is the main factor that plays a key role in the distribution of pyrolysis products, the composition of cellulose, hemicellulose, and lignin in the feedstock also determines the yield behaviour and composition of products. With the rise in pyrolysis temperature, further decomposition of intermediate components was initiated favouring the formation of lighter fractions. Comparably, species belonging to the aldehyde chemical family had the highest share of bio-oil components in all the investigated feedstocks. Overall, the present study shows a good agreement with the experimental study reported in the literature, confirming its validity as a predictive tool for the biomass pyrolysis process.     

A cyclically pressurised soaking process for the hydration and aromatisation of cannellini beans

Hydrating beans before cooking reduces cooking time, increases their tenderness and weight and improves their appearance after cooking. In this paper, we describe a process of cyclically pressurised soaking for the rapid hydration of cannellini beans at room temperature. This hydration process is approximately ten-fold faster than the traditional soaking procedure, and the microbial load developed by the end of this process is much lower compared to that obtained using the traditional process. This bean hydration process was achieved with a new extraction technique using the Naviglio extractor, which subjected the water containing the beans to cycles of pressurisation in which the pressure values ranged between 0 (atmospheric pressure) and 10 bar. This innovative hydration process (I) reduced the time required for the complete hydration of the beans to approximately 60 min and produced a product saturated with the same final amount of moisture as the product obtained from the conventional soaking process (T) that lasts 12–20 h. The numerical simulation of the hydration process (I) has provided useful indications on how the diffusion of humidity inside the beans occurred during the pressurised soaking process. The treated beans were packaged, and organoleptic tests, including taster panel tests, were conducted. Finally, the aromatisation of the legumes was conducted in conjunction with the hydration process to introduce flavouring elements used in some famous traditional recipes for Italian cuisine.     

Detecting the imprints of past clear-cutting on riparian forest plant communities along a Mediterranean river

In riparian forests, clear-cutting causes long-lasting changes in both riparian and aquatic biota. In this work, we examined if past clear-cutting events occurred at different times have imprints on riparian forests in a Mediterranean river in central Italy. We carried out a randomized, plot-based vegetation survey of riparian forests in systematically sampled 500 m-long sectors along the whole river, dividing the riparian zone into two internal and two external strips. From historical aerial photos, past clear-cutting events within plots were detected and classified in age classes: (i) cut in the past 8 years (recent); (ii) cut between 8 and 19 years ago (intermediate); (iii) no signs of clear-cutting in the last 19 years (distant). We analyzed the responses of vegetation to clear-cutting and strip position. Alien species richness was higher and woody species richness was lower in recently clear-cut areas compared to those with a distant clear-cutting event. Moreover, recently cut woods had more alien and synanthropic species. Intermediate clear-cut areas had higher levels of invasion by alien species compared to areas with distant cut. Riparian forests of internal strips are impacted by clear-cutting, but seem to recover in 8–19 years thanks to their natural resilience. Conversely, recent or intermediate clear-cutting events did not affect any of the investigated vegetation attributes in the external strips since such forests were already invaded by alien and synanthropic species after human disturbance. Our results confirm that clear-cutting events can have long-lasting effects on Mediterranean riparian forests, confirming the vulnerability of river ecosystems to clear-cutting and suggesting the need for more caution in management practices to improve the conservation status of riparian forests.