36 research outputs found
The Beaker phenomenon and the genomic transformation of northwest Europe
From around 2750 to 2500 bc, Bell Beaker pottery became widespread across western and central Europe, before it disappeared between 2200 and 1800 bc. The forces that propelled its expansion are a matter of long-standing debate, and there is support for both cultural diffusion and migration having a role in this process. Here we present genome-wide data from 400 Neolithic, Copper Age and Bronze Age Europeans, including 226 individuals associated with Beaker-complex artefacts. We detected limited genetic affinity between Beaker-complex-associated individuals from Iberia and central Europe, and thus exclude migration as an important mechanism of spread between these two regions. However, migration had a key role in the further dissemination of the Beaker complex. We document this phenomenon most clearly in Britain, where the spread of the Beaker complex introduced high levels of steppe-related ancestry and was associated with the replacement of approximately 90% of Britainâs gene pool within a few hundred years, continuing the east-to-west expansion that had brought steppe-related ancestry into central and northern Europe over the previous centuries
Measurement of the electron reconstruction efficiency at LHCb
The single electron track-reconstruction efficiency is calibrated using a sample corresponding to 1.3 fbâ1 of pp collision data recorded with the LHCb detector in 2017. This measurement exploits B+â J/Ï(e+eâ)K+ decays, where one of the electrons is fully reconstructed and paired with the kaon, while the other electron is reconstructed using only the information of the vertex detector. Despite this partial reconstruction, kinematic and geometric constraints allow the B meson mass to be reconstructed and the signal to be well separated from backgrounds. This in turn allows the electron reconstruction efficiency to be measured by matching the partial track segment found in the vertex detector to tracks found by LHCb's regular reconstruction algorithms. The agreement between data and simulation is evaluated, and corrections are derived for simulated electrons in bins of kinematics. These correction factors allow LHCb to measure branching fractions involving single electrons with a systematic uncertainty below 1%
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Study of the and states in decays
The decays are studied using a data
set corresponding to an integrated luminosity of 9fb collected with the
LHCb detector in proton-proton collisions between 2011 and 2018. Precise
measurements of the ratios of branching fractions with the intermediate
, and states are reported. The decay
of with is observed for the first time with a significance of 5.1
standard deviations. The mass differences between the ,
and states are measured to be resulting in the
most precise determination of the mass. The width of the
state is found to be below 5.2MeV at 90\% confidence level. The
Breit-Wigner width of the state is measured to be which is inconsistent with zero by 5.5 standard deviations
Mass spectrometric strategies for the investigation of biomarkers of illicit drug use in wastewater
The analysis of illicit drugs in urban wastewater is the basis of wastewaterâbased epidemiology (WBE), and has received much scientific attention because the concentrations measured can be used as a new nonâintrusive tool to provide evidenceâbased and realâtime estimates of communityâwide drug consumption. Moreover, WBE allows monitoring patterns and spatial and temporal trends of drug use. Although information and expertise from other disciplines is required to refine and effectively apply WBE, analytical chemistry is the fundamental driver in this field. The use of advanced analytical techniques, commonly based on combined chromatographyâmass spectrometry, is mandatory because the very low analyte concentration and the complexity of samples (raw wastewater) make quantification and identification/confirmation of illicit drug biomarkers (IDBs) troublesome. We review the mostârecent literature available (mostly from the last 5 years) on the determination of IDBs in wastewater with particular emphasis on the different analytical strategies applied. The predominance of liquid chromatography coupled to tandem mass spectrometry to quantify target IDBs and the essence to produce reliable and comparable results is illustrated. Accordingly, the importance to perform interâlaboratory exercises and the need to analyze appropriate quality controls in each sample sequence is highlighted. Other crucial steps in WBE, such as sample collection and sample preâtreatment, are briefly and carefully discussed. The article further focuses on the potential of highâresolution mass spectrometry. Different approaches for target and nonâtarget analysis are discussed, and the interest to perform experiments under laboratoryâcontrolled conditions, as a complementary tool to investigate related compounds (e.g., minor metabolites and/or transformation products in wastewater) is treated. The article ends up with the trends and future perspectives in this field from the authorsâ point of view