253 research outputs found
A local effect model-based interpolation framework for experimental nanoparticle radiosensitisation data
A local effect model (LEM)-based framework capable of interpolating nanoparticle-enhanced photon-irradiated clonogenic cell survival fraction measurements as a function of nanoparticle concentration was developed and experimentally benchmarked for gold nanoparticle (AuNP)-doped bovine aortic endothelial cells (BAECs) under superficial kilovoltage X-ray irradiation. For three different superficial kilovoltage X-ray spectra, the BAEC survival fraction response was predicted for two different AuNP concentrations and compared to experimental data. The ability of the developed framework to predict the cell survival fraction trends is analysed and discussed. This developed framework is intended to fill in the existing gaps of individual cell line response as a function of NP concentration under photon irradiation and assist the scientific community in planning future pre-clinical trials of high Z nanoparticle-enhanced photon radiotherapy
Delineating multiple salinization processes in a coastal plain aquifer, northern China: hydrochemical and isotopic evidence
Groundwater is an important water resource for agricultural irrigation and urban
and industrial utilization in the coastal regions of northern China. In the
past 5 decades, coastal groundwater salinization in the YangâDai river
plain has become increasingly serious under the influence of anthropogenic
activities and climatic change. It is pivotal for the scientific management
of coastal water resources to accurately understand groundwater salinization
processes and their causative factors. Hydrochemical (major ion and trace
element) and stable isotopic (δ18O and δ2H) analysis of
different water bodies (surface water, groundwater, geothermal water and
seawater) were conducted to improve understanding of groundwater salinization
processes in the plain's Quaternary aquifer. Saltwater intrusion due to
intensive groundwater pumping is a major process, either by vertical
infiltration along riverbeds which convey saline surface water inland, and/or
direct subsurface lateral inflow. Trends in salinity with depth indicate that
the former may be more important than previously assumed. The proportion of
seawater in groundwater is estimated to have reached up to 13âŻ% in shallow
groundwater of a local well field. End-member mixing calculations also
indicate that the geothermal water with high total dissolved solids (up to 10.6âŻgâŻLâ1) with
depleted stable isotope compositions and elevated strontium concentrations
(>âŻ10âŻmgâŻLâ1) also mixes locally with water in the overlying
Quaternary aquifers. This is particularly evident in samples with elevated
SrâŻââŻCl ratios (>âŻ0.005 mass ratio). Deterioration of groundwater
quality by salinization is also clearly exacerbated by anthropogenic
pollution. Nitrate contamination via intrusion of heavily polluted marine
water is evident locally (e.g., in the Zaoyuan well field); however, more
widespread nitrate contamination due to other local sources such as
fertilizers and/or domestic wastewater is evident on the basis of NO3âŻââŻCl
ratios. This study provides an example of how multiple geochemical indicators
can delineate different salinization processes and guide future water
management practices in a densely populated water-stressed coastal region
Parity nonconservation in electron recombination of multiply charged ions
We discuss a parity nonconserving asymmetry in the cross section of KLL
dielectronic recombination of polarized electrons on the hydrogen-like ions
with . This effect is strongly enhanced because of the
near-degeneracy of doubly-excited states of opposite parity in He-like
ions. For ions with the asymmetry is of the order of . For
a level crossing takes place, leading to the PNC asymmetry of
, which is times greater than the basic strength of
the weak interaction in atoms.Comment: 11 pages, 5 figures; v.2: sign errors in Eqs.(29-32,38) corrected,
figs.4,5 and related discussion change
Fe XVII X-ray Line Ratios for Accurate Astrophysical Plasma Diagnostics
New laboratory measurements using an Electron Beam Ion Trap (EBIT) and an
x-ray microcalorimeter are presented for the n=3 to n=2 Fe XVII emission lines
in the 15 {\AA} to 17 {\AA} range, along with new theoretical predictions for a
variety of electron energy distributions. This work improves upon our earlier
work on these lines by providing measurements at more electron impact energies
(seven values from 846 to 1185 eV), performing an in situ determination of the
x-ray window transmission, taking steps to minimize the ion impurity
concentrations, correcting the electron energies for space charge shifts, and
estimating the residual electron energy uncertainties. The results for the
3C/3D and 3s/3C line ratios are generally in agreement with the closest theory
to within 10%, and in agreement with previous measurements from an independent
group to within 20%. Better consistency between the two experimental groups is
obtained at the lowest electron energies by using theory to interpolate, taking
into account the significantly different electron energy distributions.
Evidence for resonance collision effects in the spectra is discussed.
Renormalized values for the absolute cross sections of the 3C and 3D lines are
obtained by combining previously published results, and shown to be in
agreement with the predictions of converged R-matrix theory. This work
establishes consistency between results from independent laboratories and
improves the reliability of these lines for astrophysical diagnostics. Factors
that should be taken into account for accurate diagnostics are discussed,
including electron energy distribution, polarization, absorption/scattering,
and line blends.Comment: 29 pages, including 7 figure
Isotope shift in the dielectronic recombination of three-electron ^{A}Nd^{57+}
Isotope shifts in dielectronic recombination spectra were studied for Li-like
^{A}Nd^{57+} ions with A=142 and A=150. From the displacement of resonance
positions energy shifts \delta E^{142,150}(2s-2p_1/2)= 40.2(3)(6) meV
(stat)(sys)) and \delta E^{142,150}(2s-2p_3/2) = 42.3(12)(20) meV of 2s-2p_j
transitions were deduced. An evaluation of these values within a full QED
treatment yields a change in the mean-square charge radius of ^{142,150}\delta
= -1.36(1)(3) fm^2. The approach is conceptually new and combines the
advantage of a simple atomic structure with high sensitivity to nuclear size.Comment: 10 pages, 3 figures, accepted for publication in Physical Review
Letter
Molecular dynamics study of accelerated ion-induced shock waves in biological media
We present a molecular dynamics study of the effects of carbon- and iron-ion induced shock waves in DNA duplexes in liquid water. We use the CHARMM force field implemented within the MBN Explorer simulation package to optimize and equilibrate DNA duplexes in liquid water boxes of different sizes and shapes. The translational and vibrational degrees of freedom of water molecules are excited according to the energy deposited by the ions and the subsequent shock waves in liquid water are simulated. The pressure waves generated are studied and compared with an analytical hydrodynamics model which serves as a benchmark for evaluating the suitability of the simulation boxes. The energy deposition in the DNA backbone bonds is also monitored as an estimation of biological damage, something which is not possible with the analytical model
A-Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance-Part 20
The Heart of the Matter. About Good Nursing and Telecare
Nurses and ethicists worry that the implementation of care at a distance or telecare will impoverish patient care by taking out âthe heartâ of the clinical work. This means that telecare is feared to induce the neglect of patients, and to possibly hinder the development of a personal relation between nurse and patient. This study aims to analyse whether these worries are warranted by analysing Dutch care practices using telemonitoring in care for chronic patients in the Netherlands. How do clinical practices of nursing change when telecare devices are introduced and what this means for notions and norms of good nursing? The paper concludes that at this point the practices studied do not warrant the fear of negligence and compromised relations. Quite the contrary; in the practices studied, telecare lead to more frequent and more specialised contacts between nurses and patients. The paper concludes by reflecting on the ethical implications of these changes
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