3,915 research outputs found

    Synthesis of monoalkylated calix[4]arenes via direct alkylation

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    A new one-step procedure for the synthesis of monoalkylated calix[4]arenes is presented. Reaction of calix[4]arene 1a or 1b with 1.2 equivalent of a weak base (K2CO3 in MeCN or CsF in DMF) and excess of alkylating agent affords the monoalkylated calix[4]arenes in moderate to good yield

    Effectiveness of a soil mapping geomatic approach to predict the spatial distribution of soil types and their properties

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    A soil map (1:50,000 scale) was recently produced in Sardinia (Italy) using a cost-effective GIS approach. In this study we aimed to verify, in two pilot areas and by means of statistical analysis, the effectiveness of the adopted methodology in representing and predicting the spatial distribution of soil types and properties. We focused on evaluation of 1) the influence of landforms and parent materials on soil types (WRB Reference Soil Groups) and selected soil properties and 2) the suitability of the adopted methodology for calibrating a model to predict land unit composition in terms of different soil types. Leptosols, Regosols and Cambisols were prevalent on slopes, with Leptosols being more frequent on convex slopes and Regosols and Cambisols on concave slopes. In flat areas, soil types mainly depended on the type and age of parent material, with Regosols and Cambisols prevailing on Holocene deposits and highly developed soils (mainly Luvisols) largely prevailing on Pleistocene deposits. On hard rock, Leptosols were very frequent on terrigenous metamorphic rock and frequent on granite. Besides Leptosols, Regosols occurred more frequently than Cambisols on both parent materials. Landforms strongly influenced soil depth and available water capacity. Soils on plains were deeper than those on slopes, where convex forms had shallower soils than concave forms. A similar trend applied to the available water capacity. The parent material had a significant effect on topsoil properties (thickness, texture, pH and organic carbon content) of soils belonging to the same WRB Reference Soil Group (analysis done on the most relevant WRB Reference Soil Groups, i.e. Leptosols, Regosols and Cambisols). We calibrated and tested stepwise multiple linear regressions (MLR) and general linear models (GLM) to predict the composition of map units in terms of different WRB Reference Soil Groups. The two models gave very similar results, with distinct distribution patterns that were coherent with the relationships observed between soil groups and specific combination of terrain attributes and parent materials. Results showed that both models were more reliable in predicting the absence rather than presence of a given soil type

    Comparison of Surgical Outcomes between Canaloplasty and Schlemm’s Canal Scaffold at 24 Months’ Follow-Up

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    The results of canaloplasty (CP) and Hydrus Microstent (HM) implantation were retrospectively compared at 24 months' follow-up in a cohort of subjects referred to our Institution for uncontrolled IOP in primary or secondary (e.g., pseudoexfoliative and pigmentary) open-angle glaucoma. The outcome was labelled as "complete" success, "qualified" success, or "failure" if, two years after surgery, the eyes operated on needed "no" hypotensive medications, "some" hypotensive medications, or further glaucoma surgery to attain the target IOP, respectively. Both CP and HM implant allowed significant IOP reductions, with comparable rate of clinical success and safety profile. A slightly (albeit not significant) better trend for a "complete" clinical success was observed in the CP group

    Novel Data Acquisition System for Silicon Tracking Detectors

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    We have developed a novel data acquisition system for measuring tracking parameters of a silicon detector in a particle beam. The system is based on a commercial Analog-to-Digital VME module and a PC Linux based Data Acquisition System. This DAQ is realized with C++ code using object-oriented techniques. Track parameters for the beam particles were reconstructed using off-line analysis code and automatic detector position alignment algorithm. The new DAQ was used to test novel Czochralski type silicon detectors. The important silicon detector parameters, including signal size distributions and signal to noise distributions, were successfully extracted from the detector under study. The efficiency of the detector was measured to be 95 %, the resolution about 10 micrometers, and the signal to noise ratio about 10.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 6 pages, LaTeX, 5 eps figures. PSN TUGP00

    Sunflower and peanut emergency : initial development under sugarcane mulch.

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    The research aimed to evaluate the effect of residual sugarcane mulch on sunflower and peanut plant emergence and initial development. Vases of 4.0 L were disposed in a randomized experimental blocks design, with four replications, in a factorial arrangement of five mulch amounts and three cultivars of each crop. The mulch treatments consisted of four increasing amounts (5, 10, 15 e 20 t ha-1) and a tester with no mulch. The sunflower cultivars were the varieties IAC-iarama and Catissol and the hybrid H-358; the peanut cultivars were IAC-Caiapó, Runner 886 and Tatu. The speed emergency index and final percentage, the plant height and shoot dry mass were evaluated. The presence of different levels of sugarcane mulch negatively influences the emergency and initial plant development mainly in peanut but also in sunflower. The negative effects are stronger especially for the runner type of peanut cultivars, while cultivar Tatu was less influenced by the mulch thickness

    Divergência genética em genótipos de girassol.

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    Uma investigação sobre a diversidade genética em 15 genótipos de girassol, por meio de 12 características agronômicas, foi implementada no Instituto Agronômico de Campinas, Brasil. Análises de variância univariada e multivariada revelaram diferenças entre os genótipos. A distância generalizada de Mahalanobis indicou um alto grau de divergência genética. Os genótipos foram agrupados em três grupos. As características início do florescimento, 50% do florescimento, número de folhas e altura da inserção do capítulo contribuíram com grande parte da divergência genética observada. Por meio desses resultados, é possível identificar materiais divergentes e complementares para o desenvolvimento de novos cultivares superiores

    Improvement of spatial contrast sensitivity threshold after surgical reduction of intraocular pressure in unilateral high-tension glaucoma.

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    PUKPOSE. To measure the effect of a surgical reduction of IOP on the spatial contrast sensitivity threshold in eyes showing a considerably increased IOP but no glaucomatous visual field defect, on white-on-white computer-assisted static perimetry. METHODS. Prospective clinical trial, lasting 36 months; 10 consecutive subjects with untreated IOP ≥ 30 mm Hg in one eye and <18 mm Hg in the fellow eye, no evidence of field damage in both eyes, best corrected visual acuity ≥ 20/20 in both eyes, and scheduled for a primary trabeculectomy in the eye showing a high IOP. The spatial contrast sensitivity threshold was measured before surgery and at each follow-up visit. RESULTS. Preoperative spatial contrast sensitivity was worse in those eyes bearing a high IOP relative to the normal fellow eyes (paired samples t-test, P < 0.0005). An improvement of contrast sensitivity threshold, exceeding the 95% confidence limits of the preoperative test-retest variability, was observed at 3, 6, and 12 cyc/deg in each surgical eye at the end of follow-up. No change was observed in the fellow untreated normal eyes. The improvement correlated directly with the amount of decrease in pressure obtained by surgery. CONCLUSIONS. Eyes with no field defects on white-on-white computer-assisted static perimetry, but bearing a IOP ≥ 30 mm Hg, show a decreased spatial contrast sensitivity. A surgically obtained reduction of IOP is paralleled by an improvement of spatial contrast sensitivity

    The Heavy Photon Search beamline and its performance

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    The Heavy Photon Search (HPS) is an experiment to search for a hidden sector photon, aka a heavy photon or dark photon, in fixed target electroproduction at the Thomas Jefferson National Accelerator Facility (JLab). The HPS experiment searches for the e+^+e−^- decay of the heavy photon with bump hunt and detached vertex strategies using a compact, large acceptance forward spectrometer, consisting of a silicon microstrip detector (SVT) for tracking and vertexing, and a PbWO4_4 electromagnetic calorimeter for energy measurement and fast triggering. To achieve large acceptance and good vertexing resolution, the first layer of silicon detectors is placed just 10 cm downstream of the target with the sensor edges only 500 μ\mum above and below the beam. Placing the SVT in such close proximity to the beam puts stringent requirements on the beam profile and beam position stability. As part of an approved engineering run, HPS took data in 2015 and 2016 at 1.05 GeV and 2.3 GeV beam energies, respectively. This paper describes the beam line and its performance during that data taking
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