Detection of Embryonic Research Topics by Analysing Semantic Topic Networks

Being aware of new research topics is an important asset for anybody involved in the research environment, including researchers, academic publishers and institutional funding bodies. In recent years, the amount of scholarly data available on the web has increased steadily, allowing the development of several approaches for detecting emerging research topics and assessing their trends. However, current methods focus on the detection of topics which are already associated with a label or a substantial number of documents. In this paper, we address instead the issue of detecting embryonic topics, which do not possess these characteristics yet. We suggest that it is possible to forecast the emergence of novel research topics even at such early stage and demonstrate that the emergence of a new topic can be anticipated by analysing the dynamics of pre-existing topics. We present an approach to evaluate such dynamics and an experiment on a sample of 3 million research papers, which confirms our hypothesis. In particular, we found that the pace of collaboration in sub-graphs of topics that will give rise to novel topics is significantly higher than the one in the control group

INFLUENCE OF PROCESS PARAMETERS ON FLUIDISED BED DRYING OF POWDERED MATERIALS

The present study reports preliminary characterization about the fluidised bed drying of powdered materials. Tests were carried out in a Lexan® lab-scale fluidised bed with solids selected to effectively surrogate powders of interest in the manufacture of pharmaceuticals. The process was monitored to correlate the temperature and the flow rate of the fluidising gas, the temperature and the moisture level in the bed, the qualitative fluidisation patterns. Bed material was characterized to assess the modifications of the population of agglomerates as a function of the operating conditions

Efeito do Potato virus X no conteúdo de fenóis totais e alcalóides em folhas de Datura stramonium

The present paper reports results of the effect of Potato virus X (PVX) on the contents of total phenols and alkaloids in leaves of Datura stramonium. A significant decrease in the contents of phenols and alkaloids was observed in leaves inoculated with PVX (X-I). However, there was an increase in the percentage of phenols in leaves rubbed with phosphate buffer (C1-I) and in leaves from the nodes immediately above, possibly induced by mechanical injury. Gas chromatography/mass spectroscopy revealed amounts of scopolamine in samples submitted to all treatments, except X-I, in which the amount of this alkaloid was low. High amounts of an unidentified compound (molecular ion m/z 302 and a prominent peak at m/z 129) were noted in extracts from leaves X-I, C1-I and leaves from the nodes immediately above the leaves inoculated with PVX. It is suggested that the synthesis and accumulation of the unidentified compound is a result of stress from mechanical injury and virus inoculation.O presente trabalho relata resultados sobre a ação do Potato virus X (PVX) no conteúdo de fenóis totais e alcalóides em folhas de Datura stramonium. Uma diminuição significativa no conteúdo dessas substâncias foi observada nas folhas inoculadas com o PVX (X-I). Entretanto, houve um aumento na porcentagem de fenóis nas folhas friccionadas com tampão fosfato (C1-I) e nas acima das friccionadas, possivelmente induzido por injúria mecânica. Cromatografia gasosa/espectroscopia de massas revelou quantidades de escopolamina nas amostras submetidas a todos os tratamentos, exceto em X-I, no qual a quantidade deste alcalóide foi baixa. Altas quantidades de uma substância não identificada (íon molecular m/z 302 e um proeminente pico a m/z 129) foram notadas em extratos a partir de folhas dos tratamentos X-I, C1-I e nas acima das inoculadas com o PVX. Sugere-se que a síntese e acúmulo da substância não identificada é um resultado do estresse causado pela injúria mecânica e pelo vírus

ASSESSMENT OF KINETICS FOR BUTANOL PRODUCTION BY CLOSTRIDIUM ACETOBUTYLICUM

The economic scenario established at the beginning of the third millennium has revived the interest in Acetone-Butanol-Ethanol (ABE) fermentations. Recent developments in molecular techniques applied to solventogenic microrganisms in combination with recent advances in fermentation systems and downstream processing have contributed to improve ABE fermentation processes feasibility and competitiveness. The challenges raised over the last years as regards ABE production may be synthesized in: i) use of renewable resources as substrate; ii) selection of strains characterized by high ABE productivity; iii) development of new fermentation systems; iv) development of new downstream strategies for enhanced solvent recovery. The selection of unconventional substrates is favoured by the ability of clostridia strains to metabolize a wide range of carbohydrates like glucose, lactose, etc...., typically present in wastewater streams e.g. from food industries. Even though clostridia have been proven successful to produce ABE, information about kinetics of substrate conversion, cell growth and butanol production is still lacking. Studies available in literature most typically regard batch tests whose results do not apply easily to continuous processes. The strong interaction between the growth/acidogenesis phase and the solventogenesis phase should be taken into account. The reactor systems investigated for the ABE fermentation belong to the batch and fed-batch typologies. Some attempts are reported in literature regarding continuous fermentation by means of clostridia strains confined in the reactor by immobilization or cell-recycling. The present study reports the preliminary results of a research activity aiming at investigating the feasibility of the ABE production by Clostridium acetobutylicum ATCC824 in a continuous biofilm reactor adopting cheese whey as feedstock. The contribution regards the characterization of the kinetics related to the ABE production process by free C. acetobutylicum ATCC824 adopting as medium lactose solutions, in order to emulate the cheese whey. The conversion process is characterized in terms of cells, acids, solvents, pH, gas composition and total organic compounds as a function of time. Results are worked out to assess the kinetics of the cells growth and of the ABE production. The yields of the carbon source in cells, acids and solvents are also assessed. The investigation is carried out adopting both batch reactors and two continuous reactors. In particular, the continuous reactors are equipped to operate under controlled conversion regimes, acidogenesis or solventogenesis. Tests carried out under batch conditions show that: i) cells growth follows the Monod kinetics for lactose concentration (CL) smaller than 100 g/L; ii) the butanol specific production rate increases linearly with CL; iii) the lactose conversion - measured at the end of the solventogenesis phase - decreases with CL; iv) the selectivity of butanol with respect to total solvents increases with CL and stabilizes at about 72%W for CL larger than 30 g/L. Preliminary tests carried out with the continuous reactor operated under solventogenesis regime show that steady state establishes with respect to cells and metabolites concentration at dilution rate of about 0.04 h-1

Características micromorfológicas e químicas das ceras cuticulares de Cleistes (Orchidaceae, Pogonieae)

Micromorphology of cuticular waxes of leaves of 13 species of South American Cleistes Rich. ex Lindl. (Vanilloideae: Pogonieae) were observed by scanning electron microscopy. Chemical constituents of the waxes of eleven species were identified by gas chromatography. The observations were carried out with individuals of native populations occurring in South, Southeastern, Northeastern and Central-Western Brazil. The micromorphology of the cuticular waxes varied from amorphous deposits to parallel stacked platelets. The latter morphological pattern seems to be more common in plants from dryer habitats. Alkyl acids are predominant constituents of waxes of most species. Alkyl alcohols predominate in other species and alkanes are predominant in only one of the studied species. Alkyl esters, monoglycerides and sterols are minor compounds, having not been detected in some species. Either hexadecanoic or octadecanoic are main homologues of alkyl acids; regarding alkyl alcohol homologue distribution, hexacosanol, octacosanol and triacontanol predominates; pentacosane, heptacosane, octacosane, nonacosane and hentriacontane predominate in alkane homologue distributions. No correlation exists between chemical composition and micromorphology of the wax deposits. Stomata distribution restricted to the adaxial or on both foliar surfaces, morphology of wax deposits and chemical composition do not correlate with molecular phylogeny. On the other hand, all these attributes may be useful for species characterization and distinction between species.A micromorfologia das ceras cuticulares em folhas de 13 espécies de Cleistes Rich. ex Lindl. (Vanilloideae: Pogonieae) sul-americanas foram observadas com o auxílio de um microscópio eletrônico de varredura. Os componentes químicos das ceras epicuticulares de 11 espécies foram identificados por cromatografia gasosa. Todas as análises foram feitas com amostras coletadas no campo, a partir de populações nativas, nas regiões sul, sudeste, nordeste e centro-oeste do Brasil. A micromorfologia das ceras epicuticulares variou desde depósitos amorfos até pequenas placas paralelamente orientadas. A presença de ceras epicuticulares formando placas é mais comum em plantas que ocorrem em ambientes secos. Ácidos alquílicos são os principais constituintes das ceras epicuticulares da maioria das espécies do gênero. Álcoois alquílicos predominam em outras espécies e alcanos são os principais constituintes das ceras de uma das espécies. Ésteres alquílicos, mono-glicerídeos e esteróis são encontrados em pequenas quantidades, e não estão presentes em todas as espécies. O ácido hexadecanóico ou o octadecanóico são os homólogos principais de ácidos alquílicos; em relação à distribuição de álcoois alquílicos, predominam octacosanol e triacontanol; pentacosano, heptacosano, octacosano, nonacosano e hentriacontano predominam nas distribuições de homólogos alcanos. De acordo com nossos dados não existe correlação entre a composição química e a micromorfologia das ceras. A posição dos estômatos, distribuídos por toda a face adaxial ou em ambas as superfícies da folha, a micromorfologia e a composição química das ceras epicuticulares não possuem correlação com a filogenia do grupo. Por outro lado, todas essas características podem ser usadas na caracterização e distinção entre as espécies do gênero

Modelling of a chemical looping combustion system equipped with a two- stage fuel reactor

The proper selection of the oxygen carrier and the correct design of the fuel reactor represent the main criticalities for the success of the chemical looping combustion (CLC) process for solid fuels. In a previous work (1) a two-stage fuel reactor (t-FR), consisting of two bubbling beds in series (bottom bed and top bed) (Fig. 1), has been proposed in order to overcome the limitations of a single-stage fuel reactor (poor char conversion, slip of unburnt volatiles, extensive elutriation of char fines). A mathematical model has been developed with the aim of assessing the performances of the two-stage fuel reactor varying operating conditions in comparison with a benchmark case consisting of a single-stage fuel reactor equipped with and without carbon stripper. The t-FR showed the best performances in terms of combustion efficiency, volatile matter and char conversion, carbon-to-CO2 conversion efficiency and loss of elutriated carbon for all the operating conditions investigated. In the present work a further enhancement of the model has been developed in order to study the hydrodynamics of the proposed multiple interconnected fluidized beds (MIFB) system for the CLC of solid fuels. The modelled system consists of the two-stage fuel reactor, a riser (Air Reactor) and non-mechanical valves for the regulation of the solid circulation between the two reactors. The different parts are considered as separate blocks mutually interconnected (Fig. 1). The operation of the system has been simulated by considering chemical looping combustion of a bituminous coal with an oxygen carrier consisting of CuO supported on zirconia. The numerical simulation has been addressed to evaluate (at steady state) the solid circulation rate, the temperature and oxidation degree of solids and concentrations profiles of gaseous species at the exit of both air and fuel reactors, with the utilization of proper constitutive equations for each block. Specific attention has been paid to the fluid dynamic behaviour of the t-FR. Results of the CLC-MIFB system with the t-FR are presented and the effects on the feasibility of the process of a variation in operating conditions are commented. Please click Additional Files below to see the full abstract

Laser Diagnostics of Hydrodynamics and Gas-Mixing in the Splash Zone of Gas-Fluidized Beds

The hydrodynamic patterns of gas flow associated with bubbles bursting at the surface of gas-fluidized beds have been investigated by means of planar laser induced fluorescence using acetone as diffusive gas tracer. The flow structures generated by the eruption of an isolated bubble have been characterized as a function of bed material size and of bubble injection level

A twin-bed test reactor for characterization of calcium looping sorbents

The reduction of sorbent CO2 capture capacity and the extent of particle attrition over iterated cycles are relevant to design of Calcium Looping processes (1-2). Thermogravimetric analyzers or fluidized bed reactors are generally used to evaluate the sorbent performance. One drawback of these reactors is that they do not reproduce the thermal history that is actually experienced by sorbent particles in real looping cycles. In this study, a novel experimental technique is proposed to overcome this limitation. The apparatus consists of two interconnected fluidized bed reactors operating as calciner and carbonator, respectively (Fig. 1). The two reactors are connected each other by a duct (whose openings can be located at adjustable level above the gas distributor) which permits pneumatic transport of the solids between the reactors. Silica sand is used as buffering inert material to prevent excessive temperature fluctuations due to solid transport and chemical reactions. The operating conditions (fluidization velocity and duct height) of the reactor have been tuned to maximize transfer of the sorbent at each cycle, while limiting the transport of sand (Fig. 2). Further tests were carried out to simulate multiple calcination/carbonation cycles (Fig. 3). Under the optimal experimental conditions more than 95% collection efficiency of the limestone was obtained while less than half of the sand was transferred. Additional tests were carried out at high temperature but under non-reacting conditions, so as to simulate the real thermal history of the particles. Please click Additional Files below to see the full abstract