534 research outputs found

    Searches for invisibly decaying Higgs bosons with the CMS detector

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    Searches for invisibly decaying Higgs bosons using the Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) and their interpretations are described. These searches are motivated both by a desire to characterise the newly observed Higgs boson, and by the cosmological observation of very weakly interacting matter in the universe, which is called dark matter. In order to provide context for these searches, introductions to the Standard Model (SM) of particle physics and several extensions to the SM which incorporate dark matter are given. The searches described in this thesis use data recorded in proton-proton collisions in 2012 and focus on the most sensitive mode, Vector Boson Fusion (VBF) production. The first search uses 19.5 fb 1 of data promptly reconstructed in 2012 and results in an observed (expected) limit on the invisible branching fraction of the 125 GeV Higgs boson, B (H -> inv), of 0.65 (0.49) at the 95% confidence level (CL) [1]. The second search uses 19.2 fb 1 of data collected using triggers with looser thresholds and reconstructed later, in 2013. This search resulted in an observed (expected) limit on B (H -> inv) of 0.57 (0.40) at the 95% CL [2]. Combinations of these searches with searches in other production channels are also described, the most sensitive of which results in an observed (expected) limit on B (H -> inv) of 0.36 (0.30) at 95% CL [3]. Projections of the sensitivity of these analyses in Run 2 and interpretations of their results as limits on various models of dark matter are also given [4].Open Acces

    Study of strawberry flavored milk under pulsed electric field processing

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    Few studies exist on flavored milk processed by pulsed electric fields (PEF). The main concern is product stability. This study aimed to analyze the degradation of coloring agent Allura Red in strawberry milk under PEF. Four systems were tested containing Allura Red: two commercial milks and two model systems. PEF conditions were 40 kV/cm, 48 pulses (2.5 μs), and 55 °C; coloring agent was quantified via RP-HPLC. After processing, only minor changes were observed in color, Allura Red concentration, and pH. During storage (32 d) at refrigerated conditions (4 °C) commercial samples maintained pH above 6. Model systems dropped below pH 6 after 10 days of storage. Color of samples showed important decrease in a⁎; hue angle and chroma changed during storage. HPLC analysis reported a bi-phasic effect in Allura Red concentrations versus time. Concentration changed, reaching a maximum value during the middle of storage, possibly attributed to microbial growth, pH reduction, or interaction of proteins. However, PEF affected the stability of Allura Red in milk when additional ingredients were not added to the product

    Study of strawberry flavored milk under pulsed electric field processing

    Get PDF
    Few studies exist on flavored milk processed by pulsed electric fields (PEF). The main concern is product stability. This study aimed to analyze the degradation of coloring agent Allura Red in strawberry milk under PEF. Four systems were tested containing Allura Red: two commercial milks and two model systems. PEF conditions were 40 kV/cm, 48 pulses (2.5 μs), and 55 °C; coloring agent was quantified via RP-HPLC. After processing, only minor changes were observed in color, Allura Red concentration, and pH. During storage (32 d) at refrigerated conditions (4 °C) commercial samples maintained pH above 6. Model systems dropped below pH 6 after 10 days of storage. Color of samples showed important decrease in a⁎; hue angle and chroma changed during storage. HPLC analysis reported a bi-phasic effect in Allura Red concentrations versus time. Concentration changed, reaching a maximum value during the middle of storage, possibly attributed to microbial growth, pH reduction, or interaction of proteins. However, PEF affected the stability of Allura Red in milk when additional ingredients were not added to the product

    Iron-Catalyzed Heck-Type Alkenylation of Functionalized Alkyl Bromides

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    The ability of iron to controllably generate alkyl radicals from alkyl halides as a key step in atom transfer radical polymerization (ATRP) has been adapted to facilitate a formal Heck cross-coupling between styrenes and functionalized alkyl bromides. A simple FeCl<sub>2</sub> catalyst in a coordinating solvent gave excellent activity without the need for expensive ligands. Tertiary, secondary, and even primary alkyl bromides are tolerated to give the products in moderate to good yields (up to 94% yield). The easily accessible reagents and operational simplicity make this reaction a method of choice for the alkenylation of alkyl halides, especially for functionalized tertiary alkyl halides, which are difficult to target by classic palladium-catalyzed Heck reactions because of the competing β-hydride elimination

    Early Neolithic Pits at Principal Place, Shoreditch, London Borough of Hackney

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    A group of four pits excavated in the upper Walbrook valley at Principal Place, Shoreditch by MOLA in 2015 produced the largest assemblage of Early Neolithic Bowl pottery recovered to date from the City of London and its immediate surrounds. The Neolithic pits had been fortuitously preserved within part of the northern extramural Roman cemetery of Londinium and conjoining sherds of Bowl pottery were also recovered from the fill of an isolated late Roman cremation. A range of analyses showed that the vessels – comprising essentially Plain Bowl with some Decorated Bowl, the latter incorporating Peterborough Ware traits – were probably locally made and had been used to process dairy products and to stew beef and mutton (though not pork). Radiocarbon dating of the lipids absorbed within the vessel walls – employing a novel technique developed at the University of Bristol – suggest that the pottery was being used in the mid-fourth millennium cal BC. The pits also contained small assemblages of struck flint, fauna (some burnt) and archaeobotanical remains (some intrusive) and may have been filled using material drawn from a long-vanished ‘pre-pit’ source, possibly a midden; they presumably represent episodic activity on the part of semi-sedentary Neolithic communities
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