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It is well known that a small number of graphene nanoparticles embedded in polymers enhance the electrical conductivity; the polymer changes from being an insulator to a conductor. The graphene nanoparticles induce several quantum effects, non-covalent interactions, so the percolation threshold is accelerated. We studied five of the most widely used polymers embedded with graphene nanoparticles: polystyrene, polyethylene-terephthalate, polyether-ketone, polypropylene, and polyurethane. The polymers with aromatic rings are affected mainly by the graphene nanoparticles due to the π-π stacking, and the long-range terms of the dispersion corrections are predominant. The polymers with linear structure have a CH-π stacking, and the short-range terms of the dispersion corrections are the important ones. We used the action radius as a measuring tool to quantify the non-covalent interactions. This action radius was the main parameter used in the Monte-Carlo simulation to obtain the conductivity at room temperature (300 K). The action radius was the key tool to describe how the percolation transition works from the fundamental quantum levels and connect the microscopic study with macroscopic properties. In the Monte-Carlo simulation, it was observed that the non-covalent interactions affect the electronic transmission, inducing a higher mean-free path that promotes the efficiency in the transmission.

This paper reports the design of a biosensor for sensitive, low-cost measurement of lead in drinking water. The biosensor uses a genetically-modified strain of Escherichia coli , which serves as both signal amplifier and reporter of lead in water, measured via colour change. We developed the PlomBOX measurement platform to image this colour change and we demonstrate its capability to detect concentrations as low as the World Health Organisation upper limit for drinking water of 10 ppb. Our approach does not require expensive infrastructure or expert operators, and its automated sensing, detection and result visualisation platform is user-friendly and robust compared to existing lead biosensors—critical features to enable measurement by non-experts at the point of use. Adriana Dias and co-authors report a low-cost bioassay for the detection of low concentrations of lead in drinking water. The approach uses a genetically modified strain of Escherichia coli , which serves as both signal amplifier and reporter of lead in water, measured via colour change.

A windowless supersonic gas jet target (SUGAR) has been put in operation recently in Mexico. It is the first target of its kind in the country and the region. New research opportunities become available with this facility through the study of the direct beam-gas interaction: nuclear physics and astrophysics, atomic physics, interaction of radiation with matter and other interdisciplinary applications. A general description of the apparatus and its commissioning is given here. Air, nitrogen and argon jets were produced. Proton and deuteron beams were used to measure key parameters of the system to compare with theoretical estimates. In addition, as a first study case, we present data from the N14(d,α)C12 reaction, at center of mass energies between 1.9 and 3.0 MeV with an E-ΔE telescope detector at 35°. Excitation functions for several excited states were constructed and an O16 resonance at 22.72 MeV was confirmed.

The γ -ray flux inside La Guadalupe mine, the selected site for the construction of the underground laboratory LABChico in Mexico, is reported for energies below 3 MeV. Data were recorded with a 0.669 kg thallium-activated sodium iodide (NaI) crystal detector deployed for 3.6 hr. The detector response was calculated via Monte Carlo simulations with GEANT4 and validated against point-like calibration sources, and the γ -ray spectrum was extracted using an unfolding technique. The γ -ray flux above 250 keV and below 3 MeV is 0.1768 γ /cm 2 /s. The two most intense γ -rays in the natural radioactive background, 40 K and 208 Tl, were identified. The flux measured for these isotopes is 0.0363 ± 0.0020  γ /cm 2 /s and 0.0016 ± 0.0005  γ /cm 2 /s, respectively. A γ -ray spectrometry analysis of rock samples showed 674.0 ± 2.0 Bq/kg, 24.0 ± 0.1 Bq/kg, and 17.7 ± 0.2 Bq/kg, of 40 K, 232 Th, and 238 U, respectively. These results are compared with deep underground facilities such as SURF, SNOLAB, Boulby, Modane, and Gran Sasso, with differences observed mainly due to the rock composition. Geotechnical studies of the mine and its rock composition are also reported.

Towards the end of 2017, a new beam line was commissioned at the Laboratorio Nacional de Espectrometría de Masas con Aceleradores (LEMA) at Instituto de Física of the Universidad Nacional Autónoma de México (IFUNAM). Initially, LEMA was a 1 MV tandetron accelerator just dedicated to Accelerator Mass Spectrometry (AMS); nowadays, the new line adopted the main characteristics of the AMS system in a natural way: i.e., it has a high precision measurement of the beam energy and a very high and stable current (tens of μ A) depending of charge state of each isotope. The precise low energy limit around 400 keV opens a window to study reactions in the region of interest for Astrophysics. At the same time, the LEMA beam-line allows to develop experiments combining nuclear reactions with AMS, as well the developing of all of kind of Ion Beam Analysis (IBA) studies. In this work the main characteristics of the line, the ancillary systems and the perspectives for low energy measurements for nuclear studies and applications are described.

The 02+ Hoyle state and few other excited levels of 12C are fundamental for the production of carbon in the universe. In particular, the γ decay branching ratio is of utmost importance, being the only way to produce a carbon at the ground state. For the purpose to precisely investigate the decay mechanism of such states we conducted an experiment, at Laboratori Nazionali del Sud-Istituto Nazionale di Fisica Nucleare (INFN-LNS), using the reaction α + 12 C at 64 MeV. We used the 4π CHIMERA detector to detect both α and γ 12 C decay channels. Details of the experiment and preliminary results are discussed in the paper.

The γ-decays of 12C excited levels (the Hoyle state 0+ at 7.65 MeV and the 9.64 MeV 3) are essential for its production in the universe. We present here a new attempt to precisely measure such γ-decay probabilities. The measurement was performed at INFN-LNS in Catania using the 4π CHIMERA multidetector. In order to measure these low probability decay-channels we performed 4-fold coincidence measurements. The 12C target nuclei were excited by using a beam of 64 MeV α-particles produced by the Superconducting Cyclotron (CS) of INFN-LNS. The scattered α-particles and the 12C recoils were detected and identified by? E-E and ToF methods using CHIMERA telescopes. The two emitted γ-rays in the decay chain were detected and identified by using the second stage of the telescopes, CsI(Tl) scintillators, by means of fast-slow and rise time techniques. Kinematics and energy-momentum conservation laws were used to constrain the data analysis. Also the 3-α decay channel probability was measured. Such a simultaneous measurement of all known decay channels was useful to reduce the systematic errors. Preliminary results of the data analysis are reported.

We describe the use of the 4tt CHIMERA charged particle detector as a large efficiency y-ray detector. The CsI(Tl) stage of the CHIMERA telescope is used to detect and identify y-rays. The high detection efficiency and the sufficient energy resolution guaranteed by CsI(Tl) allows us to use the detector for the study of rare decays. Two examples are reported: the low probability gamma decay (<10%) of the Pygmy resonance of a radioactive nucleus as the 68Ni; the measurement of the gamma decay probability of excited levels of 12C as the Hoyle state at 7.65 (∼10−4) MeV and the 3- level at 9.64 MeV (∼107), both important for the Carbon production in stars. Future experiments made possible at INFN-LNS by the availability of the new fragment separator FRAISE are also outlined.

The World Health Organisation (WHO) presents an upper limit for lead in drinking water of 10 parts per billion ppb. Typically, to reach this level of sensitivity, expensive metrology is required. To increase the sensitivity range of low-cost devices, this paper explores the prospects of using a volume reduction technique of a boiled water sample doped with Lead-210 (210 Pb), as a means to increase the solute’s concentration. 210Pb is a radioactive lead isotope and its concentration in a water sample can be measured with e.g. High Purity Germanium (HPGe) detectors at the Boulby Underground Germanium Suite. Concentrations close to the WHO limit have not been examined. This paper presents a measurement of the volume reduction technique retaining 99±(9)% of 210Pb starting from a concentration of 1.9×10-6 ppb before reduction and resulting in 2.63×10-4 ppb after reduction. This work also applies the volume reduction technique to London tap water and reports the radioassay results from gamma counting in HPGe detectors. Among other radio-isotopes, 40K, 210Pb, 131I and 177Lu were identified at measured concentrations of 2.83×103 ppb, 2.55×10-7 ppb, 5.06×10-10 ppb and 5.84×10-10 ppb in the London tap water sample. This technique retained 90±50% of 40K. Stable lead was inferred from the same water sample at a measured concentration of 0.012 ppb, prior to reduction.

The genetic variant rs10974944 (C>G) in the JAK2 gene is associated with a higher risk of myeloproliferative neoplasms (MPNs) by increasing the probability of the somatic mutation V617F in the JAK2 protein. For this reason, we evaluated the distribution of rs10974944 in Mexican populations, including published data from association studies in worldwide populations. We analyzed five Mestizo (admixed; n = 200) and four Native American (n = 200) population samples from Mexico, representing the northern, central, western, and southern regions of the country, genotyping rs10974944 by quantitative PCR using Taqman probes. Allele and genotype frequencies were estimated in each population sample. The wild-type allele C, the homozygous C/C, and the heterozygous C/G variants were the most frequent in all Mexican populations, and the genotype distribution in all samples was in Hardy-Weinberg equilibrium. Interestingly, genetic distances clustered most of the worldwide patient samples, including Tarahumaras and Mayas, which differed from Mexican and control samples. Although higher genetic susceptibility to MPNs could be predicted in these Native American populations, the homogeneous allele distribution among Mexican and worldwide control populations warrants analysis of further genetic and nongenetic factors. In sum, although worldwide population samples displayed homogeneous distribution for rs10974944, genetic clustering of worldwide patients supports the claimed association with MPNs.