Coulomb Excitation of 68,70Cu: First Use of Postaccelerated Isomeric Beams

We report on the first low-energy Coulomb excitation measurements with radioactive Iπ=6- beams of odd-odd nuclei 68,70Cu. The beams were produced at ISOLDE, CERN and were post-accelerated by REX-ISOLDE to 2.83  MeV/nucleon. γ rays were detected with the MINIBALL spectrometer. The 6- beam was used to study the multiplet of states (3-, 4-, 5-, 6-) arising from the π2p3/2ν1g9/2 configuration. The 4- state of the multiplet was populated via Coulomb excitation and the B(E2;6-→4-) value was determined in both nuclei. The results obtained illustrate the fragile stability of the Z=28 shell and N=40 subshell closures. A comparison with large-scale shell-model calculations using the 56Ni core shows the importance of the proton excitations across the Z=28 shell gap to the understanding of the nuclear structure in the neutron-rich nuclei with N≈40

Pricing and revenue management: The value of coordination

Cataloged from PDF version of article.The integration of systems for pricing and revenue management must trade off potential revenue gains against significant practical and technical challenges. This dilemma motivates us to investigate the value of coordinating decisions on prices and capacity allocation in a stylized setting. We propose two pairs of sequential policies for making static decisions-on pricing and revenue management-that differ in their degree of integration (hierarchical versus coordinated) and their pricing inputs (deterministic versus stochastic). For a large class of stochastic, price-dependent demand models, we prove that these four heuristics admit tractable solutions satisfying intuitive sensitivity properties. We further evaluate numerically the performance of these policies relative to a fully coordinated model, which is generally intractable. We find it interesting that near-optimal performance is usually achieved by a simple hierarchical policy that sets prices first, based on a nonnested stochastic model, and then uses these prices to optimize nested capacity allocation. This tractable policy largely outperforms its counterpart based on a deterministic pricing model. Jointly optimizing price and allocation decisions for the high-end segment improves performance, but the largest revenue benefits stem from adjusting prices to account for demand risk

A 10B-based neutron detector with stacked Multiwire Proportional Counters and macrostructured cathodes

We present the results of the measurements of the detection efficiency for a 4.7 \r{A} neutron beam incident upon a detector incorporating a stack of up to five MultiWire Proportional Counters (MWPC) with Boron-coated cathodes. The cathodes were made of Aluminum and had a surface exhibiting millimeter-deep V-shaped grooves of 45{\deg}, upon which the thin Boron film was deposited by DC magnetron sputtering. The incident neutrons interacting with the converter layer deposited on the sidewalls of the grooves have a higher capture probability, owing to the larger effective absorption film thickness. This leads to a higher overall detection efficiency for the grooved cathode when compared to a cathode with a flat surface. Both the experimental results and the predictions of the GEANT4 model suggests that a 5-counter detector stack with coated grooved cathodes has the same efficiency as a 7-counter stack with flat cathodes. The reduction in the number of counters in the stack without altering the detection efficiency will prove highly beneficial for large-area position-sensitive detectors for neutron scattering applications, for which the cost-effective manufacturing of the detector and associated readout electronics is an important objective. The proposed detector concept could be a technological option for one of the new chopper spectrometers and other instruments planned to be built at the future European Spallation Source in Sweden. These results with macrostructured cathodes generally apply not just to MWPCs but to other gaseous detectors as well.Comment: 14 pages, 9 figure

Functionalization of cellulose and chitosan in ionic liquids

Chemistry of cellulose in ionic liquids has been briefly reviewed and, accordingly, the phthalation of chitosan in these ionic solvents has been investigated. Chitosan (K) has been reacted at 100 °C for 4 hours with phthalic anhydride (PA) in ionic liquids 1-butyl-3-methylimidazolium acetate (BMIMAc) and 1-butyl-3-methylimidazolium chloride (BMIMCl) in the presence of bases, pyridine and 1,4-diazobicyclo[2.2.2] octane (DABCO), or the phthalation has been catalyzed by N-bromosuccinimide (NBS). Depending on the nature of the reaction components, the samples were prepared with molar ratios of PA to anhydroglucose unit (PA:K) from 3:1 to 10:1, including molar ratios of bases or catalyst to chitosan, ranging also from 3:1 to 10:1. All the reaction products were soluble in dimethyl sulfoxide and dimethylformamide. Both functional groups of chitosan units, -OH and -NH2, reacted, resulting in FTIR confirmed products containing esters, amide, and imide functional groups. Heating the isolated phthalated chitosan products to 200 °C led to cyclization with the formation of imide groups and elimination of water. When bases controlled the reactions, the highest degrees of substitution of DABCO product (DS = 0.80) was slightly higher than the highest DC of the reaction products obtained in the presence of pyridine (DS = 0.77). However, the presence of the N-bromosuccinimide catalyst in the system led to an increase of the degree of substitution of the functional groups of chitosan (DS = 1.75), compared with that listed above for the products resulted when the reactions were carried out in the presence of bases. The thermal stability of the chitosan derivatives obtained in the presence of a base depended primarily upon the nature of the counter ion of the ionic liquid. When the reaction was conducted in the acetate ionic liquid BMIMAc, the phthalated chitosan exhibited a lower thermal stability than that of chitosan, while when the chloride ionic liquid BMIMCl was used as solvent, the thermal stability of the phthalated chitosan increased, indicating an interference of the ionic solvents in the mechanisms of reactions. Nevertheless, the thermal behavior of the phthalated products obtained in reactions catalyzed by NBS may be correlated with the increasing degrees of substitution achieved with increased catalyst concentrations: a higher DS resulted in a higher weight loss at higher temperatures

Les papallones com a bioindicadores dels hàbitats a Catalunya: l'exemple dels prats de dall i le pastures del Parc Natural dels Aiguamolls de l'Empordà

El Parque Natural de los Aiguamolls de l’Empordà (PNAE) es uno de los espacios protegidos más conocidos y emblemáticos de Cataluña. Uno de sus hábitats más localizados y amenazados son las denominadas closes, prados de siega destinados a la producción de forraje, rodeados de canales de desagüe e inundados durante parte del invierno. Recientemente, se ha demostrado que la comunidad vegetal más típicamente asociada con estos prados es la más rica del Parque y la que alberga las especies más raras. En este trabajo se utilizan datos de mariposas diurnas (ropalóceros), obtenidos después de aplicar durante 17 años la metodología del Butterfly Monitoring Scheme, para evaluar el interés de conservación de los principales ambientes del PNAE. Las closes constituyen también para los ropalóceros el hábitat más valuoso. La coincidencia en los resultados obtenidos en dos grupos taxonómicos amplios y que ocupan niveles tróficos distintos, sumada a la alarmante regresión que han experimentado las closes en los últimos 50 años y a su singularidad en el área mediterránea, permiten considerarlas objetivamente como uno de los hábitats más amenazados del PNAE y del conjunto de Cataluña. En una segunda parte del trabajo, se analizan las respuestas de las mariposas frente al abandono de las closes y a su recuperación a partir de antiguos cultivos intensivos. Los cambios que experimentan las comunidades de mariposas pueden pasar del todo desapercibidos si los análisis se focalizan en indicadores generales (p. ej., riqueza específica y abundancia). Contrariamente, se demuestra que la respuesta de algunas especies potencialmente bioindicadoras puede ser muy acusada, si bien es necesario conocer su ecología para poder interpretarla correctamente. En concreto, se concluye que Plebejus argus representa la mejor especie bioindicadora de las peculiares condiciones ambientales propias de las closes: las poblaciones responden con descensos rapidísimos cuando estas condiciones se deterioran, y también con aumentos progresivos cuando el hábitat mejora. Además, se trata de una especie muy sedentaria que se estructura en forma de metapoblaciones, por lo cual el monitoreo de una población local refleja también las condiciones del paisaje de su entorno.Aiguamolls de l’Empordà Natural Park is one of the most important protected wetland areas on the Mediterranean coast. In this article, butterfly assemblages were used to characterize and evaluate the conservation value of the main habitat types in this protected area. Butterfly data were obtained from a number of transects walked as part of the Catalan Butterfly Monitoring Scheme, which uses a standardized methodology for monitoring butterflies. Hay meadows flooded in winter (the so-called closes) appeared always as the highest ranked habitat in terms of conservation evaluation: they have more butterflies and a slight tendency to harbour more and generally rarer species. This conclusion coincides with that of previous investigations indicating that the most diverse and rare plant communities in the whole Natural Park are present in the closes, and highlights the importance of traditionally managed hay meadows for wildlife. However, these hay meadows are in alarming decline and have become one of the most threatened habitats in this area and the whole Mediterranean region. In a second part of the article, we analysed the responses of butterfly communities once the closes are abandonned or when they are recovered from former arable fields. Changes may be completely overlooked if the analyses are focussed on general patterns for the whole community (e.g. species richness and abundance). On the other hand, several individual species showed strong population trends and some of them may be considered as true bioindicators of the narrow environmental conditions associated with this kind of habitat. In particular, we suggest that Plebejus argus represents an excellent bioindicator of these traditionally managed hay meadows: its populations always showed dramatic decreases once the closes were abadonned, overgrazed or invaded by exotic weeds, and progressive increases once the quality of the meadows improved. Moreover, this highly sedentary species exists as metapopulations and, therefore, the wealth of local populations also reflects that of the surrounding landscape.El Parc Natural dels Aiguamolls de l'Empordà (PNAE) és un dels espais protegits més coneguts i emblemàtics a Catalunya. Un dels seus hàbitats més localitzats i amenaçats són les anomenades closes, prats destinats a la producció de farratge, envoltats per canals de desguàs i bosc de ribera, inundats durant part de l'hivern i dallats periòdicament. Recentment s'ha demostrat que la comunitat vegetal més típica de les closes és la més rica del Parc i la que alberga les espècies més rares. En aquest treball s'utilitzen dades de papallones diürnes (ropalòcers), obtingudes després d'aplicar durant 17 anys la metodologia del Butterfly Monitoring Scheme, per avaluar l'interès de conservació dels principals ambients del PNAE. Les closes constitueixen l'hàbitat més valuós també per als ropalòcers. La coincidència dels resultats per a dos grups taxonòmics amplis que ocupen nivells tròfics diferents, sumada a l'alarmant regressió que han experimentat les closes en els darrers 50 anys i a la seva singularitat dins de l'àrea mediterrània, permeten considerar-les objectivament com un dels hàbitats més amenaçats del PNAE i de tot Catalunya. En una segona part del treball, s'analitzen les respostes de les papallones enfront de l'abandonament de les closes i de la seva recuperació a partir d'antics conreus intensius. Els canvis que experimenten les comunitats de ropalòcers poden passar del tot desapercebuts si les anàlisis es focalitzen en indicadors generals (p. ex., riquesa específica i abundància). Contràriament, es demostra que la resposta d'algunes espècies potencialment bioindicadores pot ser molt més acusada, encara que cal conèixer la seva ecologia per poder-la interpretar correctament. En concret, es conclou que Plebejus argus representa la millor espècie bioindicadora d'unes condicions ambientals pròpies de les closes empordaneses tradicionals: les poblacions responen amb descensos rapidíssims quan les condicions òptimes es deterioren, i també amb augments progressius quan l'hàbitat millora. A més, es tracta d'una espècie molt sedentària que s'estructura en forma de metapoblacions, per la qual cosa el monitoratge d'una població reflecteix també les condicions del paisatge del seu entorn

Phenological sensitivity and seasonal variability explain climate-driven trends in Mediterranean butterflies

Although climate-driven phenological shifts have been documented for many taxa across the globe, we still lack knowledge of the consequences they have on populations. Here, we used a comprehensive database comprising 553 populations of 51 species of north-western Mediterranean butterflies to investigate the relationship between phenology and population trends in a 26-year period. Phenological trends and sensitivity to climate, along with various species traits, were used to predict abundance trends. Key ecological traits accounted for a general decline of more than half of the species, most of which, surprisingly, did not change their phenology under a climate warming scenario. However, this was related to the regional cooling in a short temporal window that includes late winter and early spring, during which most species concentrate their development. Finally, we demonstrate that phenological sensitivity-but not phenological trends-predicted population trends, and argue that species that best adjust their phenology to inter-annual climate variability are more likely to maintain a synchronization with trophic resources, thereby mitigating possible negative effects of climate change. Our results reflect the importance of assessing not only species' trends over time but also species' abilities to respond to a changing climate based on their sensitivity to temperature

The Catalan butterfly monitoring scheme has the capacity to detect effects of modifying agricultural practices

Impacts of agricultural management practices on the receiving environment are seldom suitably assessed because environmental monitoring is costly. In this regard, data generated by already existing environmental survey networks (ESNs) may have sufficient capacity to detect effects. Here, we study the capacity of the Catalan butterfly monitoring scheme (CBMS) to detect differences in butterfly abundance due to changes in agricultural practices. As a model, we compared butterfly abundance across two landscape types according to agricultural intensification. A 2 km diameter buffer area was centered on the CBMS transect, the control group were transects located in areas where intensive agriculture represented <20% of the area; a treated group was simulated by selecting transects located in areas where intensive agriculture occupied an area over 40%. The Welch t‐test (α = 0.05 and 80% power) was used to compare butterfly abundance per section across landscape types. The capacity of the t‐test to detect changes in mean butterfly abundance, of 12 butterfly indicators relevant to farmland, was calculated annually and for 5‐, 10‐, and 15‐yr periods. Detection capacity of the t‐test depended mainly on butterfly data sample size and variability; difference in butterfly abundance was less important. The t‐test would be capable of detecting acceptably small population changes across years and sites. For instance, considering a 15‐yr period, it would be possible to detect a change in abundance below 10% of the multispecies indicators (all butterfly species, open habitat species, mobile species, and grassland indicators) and two single species (Lasiommata megera and Lycaena phlaeas). When comparisons were carried out within each year, the t‐test would only be capable of detecting a change below 30% for all butterfly species, mobile species, and L. megera. However, detection capacity rapidly improved with the addition of further years, and with 5 yr of monitoring, all indicators but Thymelicus acteon had a detection capacity below 30%. We therefore conclude that, from a statistical point of view, the CBMS data “as is” are sensitive enough for monitoring effects of changes in agricultural practices. It could be used, for instance, for the general surveillance of genetically modified crops.This work was partially supported by the Spanish Government‐funded project AGL2011‐23996 and a FI‐DGR scholarship to M. Lee from the Catalan Government

On assessment of processing variables on vertical centrifugal casting technique

The aim of the present study is to investigate the influence of the vertical centrifugal casting technique over mechanical and metallurgical properties of a hypereutectic Al–18Si alloy. Due to the inherent vibration of the centrifugal casting technique, and in order to study and understand the individual effects of the equipment vibration and the centrifugal force itself (pressure or fluid dynamics), as well as the combined effect of both, three different tests were performed: gravity casting, gravity casting with vibration and centrifugal casting. It was concluded that the metallurgical and mechanical properties of castings obtained by the centrifugal casting process depend on the combined effect of the centrifugal pressure and/or fluid dynamics and on the inherent vibration of the technique itself. Correlations between the different casting techniques and obtained mechanical and metallurgical properties are presentedFCT - Fundação para a Ciência e Tecnologi