Search

Background There is no safe level of lead in children's bodies. The US Centers for Disease Control and Prevention (CDC) estimate that more than half a million children under the age of 6 years are affected by low-level lead exposure in the USA. Low levels of lead can cause irreversible neurological and physiological damage in children. Currently, lead is investigated in the home and environment after a child has been identified as having elevated concentrations of lead in their blood; the source of lead exposure is then sought and removed. However, we seek to reverse this paradigm and allow families to engage in prevention by testing their home and environment before their child is exposed to lead. The aim of this study was to design and pilot a screening device to allow families to test their homes for lead. Methods We recruited participants for this blinded case-control study in Saint Joseph County, Indiana, USA, through community partnerships, a community lead testing event, and flyers. Participants were divided into three groups based on the age of their home: homes built before 1950; homes built between 1951 and 1978; and homes built after 1978. The post-1978 group acted as a control because lead paint was banned in 1978. Participants collected eight samples from their homes, including from soil, dust, and paint. The field team measured the concentration of lead levels in each of the eight samples at the site of collection using an X-ray fluorescence analyser. Samples were then tested at the laboratory where all identifying information was removed and workers were unaware of the age of the home the samples came from. Results from the field were then correlated with results from the laboratory using Bland-Altman plots, linear regression, and ROC curves. Informed consent was obtained and this study was approved by the University of Notre Dame Institutional Review Board. Findings We included results from 45 homes in the analysis: 17 from pre-1950 homes, 11 from 1951–78 homes; and 17 from post-1978 houses. Of the 17 pre-1950 homes, 94% had at least one finding of a lead concentration that exceeded the action level laid out by the US Environmental Protection Agency. Of the 11 1951–78 homes, 36% (4) had at least one elevated lead result, and none of the 1978 homes had an elevated lead result. Bland-Altman plot analysis showed good agreement between onsite and laboratory measurement with biases very close to zero. Correlation coefficients between field and laboratory measurements were 0·97, 0·89, and 0·92 for the soil, dust, and paint samples, respectively. The ROC curves show high sensitivity (87%), specificity (98%), and accuracy (96%). At the time of the study, the cost of the kit was approximately US$7.00, excluding laboratory fees. Interpretation This study lays the foundation for the creation of a lead sample collection kit model that can be implemented in homes, day-care centres, and schools. Although this model will not provide the participant with an in-depth lead risk assessment, it has the potential to be a tool to allow proactive screening of homes for environmental lead hazards. Our team will now work to scale up implementation with our community partners. Our goal is to distribute and test 500 kits in 2019. Funding A local private donor.

Extragenic sequences in genomes, such as microRNA and CRISPR, are vital players in the cell. Repetitive extragenic palindromic sequences (REPs) are a class of extragenic sequences, which form nucleotide stem-loop structures. REPs are found in many bacterial species at a high copy number and are important in regulation of certain bacterial functions, such as Integration Host Factor recruitment and mRNA turnover. Although a new clade of putative transposases (RAYTs or TnpA(REP)) is often associated with an increase in these repeats, it is not clear how these proteins might have directed amplification of REPs. We report here the structure to 2.6 Å of TnpA(REP) from Escherichia coli MG1655 bound to a REP. Sequence analysis showed that TnpA(REP) is highly related to the IS200/IS605 family, but in contrast to IS200/IS605 transposases, TnpA(REP) is a monomer, is auto-inhibited and is active only in manganese. These features suggest that, relative to IS200/IS605 transposases, it has evolved a different mechanism for the movement of discrete segments of DNA and has been severely down-regulated, perhaps to prevent REPs from sweeping through genomes.

Environmental Health Perspectives, 123 (5), ISSN:1552-9924, ISSN:0091-6765

Environmental Health Perspectives, 123 (7), ISSN:1552-9924, ISSN:0091-6765

Neutron decay spectroscopy has become a successful tool to explore nuclear properties of nuclei with the largest neutron-to-proton ratios. Resonances in nuclei located beyond the neutron dripline are accessible by kinematic reconstruction of the decay products. The development of two-neutron detection capabilities of the Modular Neutron Array (MoNA) at NSCL has opened up the possibility to search for unbound nuclei which decay by the emission of two neutrons. Specifically this exotic decay mode was observed in 16Be and 26O., To be published in Acta Physica Polonica B

The elemental composition of electrodeposited NiFe thin films was analyzed with particle-induced X-ray emission (PIXE). The thin films were electrodeposited on polycrystalline Au substrates from a 100 mM NiSO4, 10 mM FeSO4, 0.5 M H3BO3, and 1 M Na2SO4solution. PIXE spectra of these films were analyzed to obtain relative amounts of Ni and Fe as a function of deposition potential and deposition time. The results show that PIXE can measure the total deposited metal in a sample over at least four orders of magnitude with similar fractional uncertainties. The technique is also sensitive enough to observe the variations in alloy composition due to sample nonuniformity or variations in deposition parameters.

Central Au+Au collisions at 35 A MeV are analyzed to find the characteristics of a thermal source, in the framework of the statistical multifragmentation model SMM. A recently introduced backtracing protocol provides an effective comparison of theory and experiment. For the first time the distributions of the central source parameters (density, mass number, excitation energy) are found. The collective energy of primary fragments is also deduced. It is shown that the backtracing procedure allows an estimation of the pre-equilibrium emission. (C) 1998 Published by Elsevier Science B.V.

M. L. Begemann-Blaich, F. Cosmo, A. Ferrero, J. Hubele, G. Imme, I. Iori, J. Kempter, P. Kreutz, G. J. Kunde, W. D. Kunze, V. Lindenstruth, U. Lynen, M. Mang, A. Moroni, W. F. J. Muller, M. Neumann, B. Ocker, C. A. Ogilvie, J. Pochodzalla, G. Raciti, F. Rosenberger, T. Rubehn, H. Sann, R. Scardaoni, A. Schuttauf, C. Schwarz, W. Seidel, V. Serfling, W. Trautmann, A. Tucholski, A. Worner, and B. Zwieglinski

Multifragment disintegrations, measured for central Au + Au collisions at E/A = 35 MeV, are analyzed with the Statistical Multifragmentation Model. Charge distributions, mean fragment energies, and two-fragment correlation functions are well reproduced by the statistical breakup of a large, diluted and thermalized system slightly above the multifragmentation threshold., Latex file, 8 pages + 4 postscript figures available upon request from Dagostino@axpbo4.bo.infn.it

The charge distributions and their dependence on fragment multiplicity have been studied for the multifragmentation of 30 MeV/nucleon Xe1Au, Cu. For both targets, the charge distributions are approximately independent of the fragment multiplicity n. However, a residual systematic dependence on n is detectable at the largest values of the total charge multiplicity Nc . Such n dependence obeys a simple scaling law and suggests the presence of an entropic term possibly related to the mechanism of multifragmentation. Thermal scaling between the different bins of Nc seems to occur. PACS number~s!: 25.70.Pq In the multifragmentation of Ar1Au at 110 MeV/nucleon @1# the fragment multiplicity distribution Pn , at any given event transverse energy Et5(Eisin 2 qi , was shown to be reducible to an elementary one-fragment emission probability p by means of the well known binomial equation. It was also noticed that the logarithm of the extracted p depends linearly on 1/AEt ~Arrhenius plot!. These empirical observations were confirmed at other energies and for other systems @2#. Binomial reducibility permits the reconstruction of the probability of an n-fragment event in terms of a binomial combination of a fixed one-fragment probability, and suggests that the fragments are emitted independently with constant probability p. The linearity of the Arrhenius plots in turn suggests that the probability p has a Boltzmann-like thermal dependence

The dependence of intermediate-mass-fragment (IMF) element distributions on the multiplicity, N{sub IMF}, of detected fragments has been measured for {sup 84}Kr+{sup 197}Au collisions at E/A=35, 55, 70, 100, 200, and 400 MeV. The observed dependence can be parametrized as P(N{sub IMF}{vert_bar}Z){proportional_to}P(Z)exp({minus}c{center_dot}N{sub IMF}{center_dot}Z), where c is a beam-energy and excitation-energy dependent parameter. Previous work indicated this parameter is zero in the liquid-gas coexistence region and positive in the gaseous phase. In contrast, we observe both negative and positive values for c, revealing the meaning of this parameter to be less straightforward than previously assumed. The magnitude of c appears nonetheless to provide a nontrivial test of multifragmentation models. {copyright} {ital 1997} {ital The American Physical Society}

Multifragment disintegration has been measured with a high efficiency detection system for the reaction $Au + Au$ at $E/A = 35\ MeV$. From the event shape analysis and the comparison with the predictions of a many-body trajectories calculation the data, for central collisions, are compatible with a fast emission from a unique fragment source., 9 pages, LaTex file, 4 postscript figures available upon request from bruno@bologna.infn.it. - to appear in Phys. Lett. B

Multifragmentation for 129Xe-induced reactions on several targets (natCu, 89Y, 165Ho, 197Au) has been studied at E A = 40, 50 and 60 MeV . The probability of emitting n intermediate mass fragments is shown to be binomial at each transversal energy and reducible to an elementary binary probability p. For each target and at each bombarding energy, p shows a thermal behavior as demonstrated by linear Arrhenius plots. A nearly universal linear Arrhenius plot is observed at each bombarding energy, independent of target. The sensitivity of p to the Zthreshold points to its physical significance and rules out auto-correlation effects.

Multifragment emission is studied in 129 Xe + nat Cu reactions. The emission process for central collisions occurs on a time scale of ≈ 200 fm/c at 30 MeV/n. Intermediate-mass-fragment yields, velocity correlation functions and emission velocities of Z=6 fragments are compared with predictions of statistical decay models.

The charge (Z) distributions from intermediate energy heavy-ion reactions depend upon the multiplicity {eta} of intermediate mass fragments through a factor of the form e{sup {minus}cnZ}. Experimentally c starts from zero at low values of the transverse energy E{sub t} and reaches a saturation value at high E{sub t}. In a liquid-gas phase diagram, c = 0 for the saturated vapor, while c {gt} 0 for the unsaturated vapor. It is suggested that in the c {approx} 0 regime the source evaporates down to a sizable remnant, while for c {gt} 0 the source vaporizes completely. Percolation of a finite system portrays a behavior similar to that observed experimentally.

Cross sections were measured for fragments (4

A suite of analytical techniques was used to obtain a comprehensive picture of per- and polyfluoroalkyl substances (PFAS) in selected Canadian food packaging used for fast foods (n = 42). Particle-induced gamma ray emission spectroscopy revealed that 55% of the samples contained 10 800 μg F/m2. The highest total F (1 010 000-1 300 000 μg F/m2) was measured in molded “compostable” bowls. Targeted analysis of 8 samples with high total F revealed 4-15 individual PFAS in each sample, with 6:2 fluorotelomer methacrylate (FTMAc) and 6:2 fluorotelomer alcohol (FTOH) typically dominating. Up to 34% of the total fluorine was released from samples after hydrolysis, indicating the presence of unknown precursors. Nontargeted analysis detected 22 PFAS from 6 different groups, including degradation products of FTOH. Results indicate the use of side-chain fluorinated polymers and suggest that these products can release short-chain compounds that ultimately can be transformed to compounds of toxicological concern. Analysis after 2 years of storage showed overall decreases in PFAS consistent with the loss of volatile compounds such as 6:2 FTMAc and FTOH. The use of PFAS in food packaging such as “compostable” bowls represents a regrettable substitution of single-use plastic food packaging. ISSN:2328-8930

Position-sensitive silicon detectors with discrete position output signal levels, which have been developed for heavy ion reaction studies at the Lawrence Berkeley Laboratory are discussed. The detectors, both 300- and 5000- mu m thick, for use in Delta E-E telescopes, use a series of high and low conductivity strips on the detector p/sup +/ contact to produce a position signal with 15 discrete levels. Since the position of the signals from the strips is known, the detectors are self-calibrating against position nonlinearities. Some aspects of the fabrication of both the 300- and 5000- mu m detectors are discussed, along with their operating characteristics. Illustrative experimental results of /sup 139/La-induced reactions on /sup 40/Ca targets are presented. >