bluuebunny/crossref_metadata_2025 huggingface dataset:
Solvent Effects on the Lyoluminescence of Saccharide Dosemeters
Authors: Pitt E. , Scharmann A. , Suprihadi T.
Published: February 2017

Radiation-induced chemiluminescence (lyoluminescence, LL) of saccharides has been proposed as a method of dosimetry. Its accuracy is highly affected by solvent conditions, such as temperature, oxygen content and acidity. The basic mechanisms controlling LL have been investigated in order to reduce the statistical errors. Singlet oxygen released from disproportionation of peroxyl radicals was proposed as an energy carrier. Two singlet oxygen molecules combine their excitation energy. These collisional pairs are assumed to form the light emission centre. This model is supported by spectral analysis of luminescence emission, but a final decision on the emission process is still pending. The lifetime of singlet oxygen is known to be extended when H2O is replaced by D2O. As a consequence, enhanced LL output is expected. Experimental proof of this effect is reported. Consequences for the model of LL in saccharides are discussed.
Luminescence from Potassium Feldspars Stimulated by Infrared and Green Light
Authors: Duller G.A.T. , Bøtter-Jensen L.
Published: February 2017

A series of experiments are reported which investigate stimulated luminescence from potassium feldspar. The aim is to provide a basic phenomenological description of the response of the material to stimulation by heat, infrared radiation (875 ? 80 nm) and a green light wavelength band from 515 to 560 nm. Two conclusions are drawn: firstly it is suggested that the majority of the trapped charge responsible for the infrared stimulated luminescence signal does not give rise to a thermoluminescence signal, and secondly that a large fraction of the two optically stimulated luminescence signals originate from common traps.
Geometric Domains in Cellular Radiobiology
Authors: Rossi H.H.
Published: February 2017

A joint consideration of experimental findings and microdosimetric facts leads to the conclusion that the biological effects of ionising radiations are determined by local concentration of absorbed energy at two types of sites that differ greatly in magnitude. They are of the scale of nanometres in primary DNA damage, and of micrometres in the especially deleterious combinations of damaged DNA fragments. Both kinds depend on LET; however, at the nanometre level the dependence is much smaller. Depending on the relative contribution of the two types, the RBE values for observed biological effects can vary considerably but they may be assumed to be larger for cell transformation than for cell killing.
Assimilation of a Cylindrical Geometry Inside a Rossi Counter
Authors: Hough J.H. , Binns P.J.
Published: February 2017

Single event distributions were measured in neutron fields of different energies to appraise the response of Rossi type proportional counters operating in helix mode. Spectra acquired with tissue-equivalent and carbon walled counters operating in conventional and helix modes exemplify the intrinsic differences in chord length distributions for sensitive volumes of different shapes. An active volume in the form of an elongated cylinder was empirically assessed for the helix mode of operation following exposure to a known dose. This volume definition enabled conversion of pulse height data to absorbed dose spectra in lineal energy. Calibration of spectra was possible by identifying cut-off-edges discerned for different particle species. The dosimetric data were consistent with those obtained when running the counters conventionally and demonstrate the suitability of helix mode for time resolved kerma assessments in high energy neutron fields.
Electron Spin Resonance Windows into the Nanometre Landscape
Authors: Izzo G. , Ettinger K.V. , Holowacz J.
Published: February 2017

Ionising radiation leaves radicals and pairs of radicals in irradiated solids. The distance between observed radicals in a pair is between 0.3 and 1.0 nm. Pairs are identifiable by their electron spin resonance spectra and a method is described to calculate the distance between spins. Observations of pairs in dense polyethylene and thymine (at 77K) are described as a function of dose, for irradiations with ? rays and with 32 MeV protons.
Determination of Energy Deposited in Nanometre Sites from Ionisation Data
Authors: Bigildeev E.A. , Lappa A.V.
Published: February 2017

The paper is devoted to the ionisation method for determination of various characteristics of energy deposited in small sensitive sites of irradiated objects by ionising radiation. It is shown that traditional ionisation methods supposing the direct proportionality between energy deposited in a site and the number of ionisations in it fails to determine fluctuation characteristics in nanometre sized sites. The exact formulae connecting fluctuation characteristics of deposited energy and those of the number of ionisations, are proposed. The new radiation parameters are defined, in particular, fluctuation generalisations of W value; the most important of them are calculated for radiations of different quality using Monte Carlo techniques. The way to correct theoretical and experimental results obtained by a traditional ionisation method is proposed.
Numerical Calculation of the Radial Distribution of Dose Around the Path of a Heavy Ion
Authors: Zhang C.X. , Liu X.W. , Li M.F. , Luo D.L.
Published: February 2017

The radial dose distribution around the path of a heavy ion has been calculated by numerical integration accounting for the ejection angles of secondary electrons on the basis of classical collision dynamics and the range-energy relationship of a logarithmic polynomial. This results in a single expression for the radial dose valid for all ion energies and in better agreement with the experimental data in the radial distance between 0.1 nm and 10 nm and penumbra radius compared with those calculated using a linear or power-law relationship in the electron range-energy formula.
Radiation Signatures and Radiation Markers
Authors: McGlynn S.P. , Rupnik K. , Varma M.N. , Klasinc L.
Published: February 2017

The distribution of DNA molecular lesions is defined as the histogram of lesion occurrence probability versus lesion type and is termed a molecular lesion spectrum (MLS). The MLSs for 405 nm, 254 nm and ? ray electromagnetic radiations are investigated here, and it is shown that eight, five, four, three and two lesion sets function as very good radiation signatures; that is, MLSs based upon these lesion sets can be used to identify the causal electromagnetic radiation. The approach adopted is based on pattern recognition techniques couched in neural network formalism, the patterns being defined as vectors and their uniqueness described as a degree of vector orthogonality. The minimal lesion set for signature of the three radiations is found to consist of two lesions, thymine dimer (d) and locally multiply damaged site (lmds) lesions. This is a surprising finding, and it works only because the d lesion turns out to be a radiation marker for 254 nm radiation and the lmds lesion to be a radiation marker for ? rays. Since these findings about signatures and markers are important from safety, insurance and medical aspects, it is well to caution that only three radiations, all electromagnetic, have been investigated here. Work on particulate and other electromagnetic radiations is underway.
Indoor Radon Measurements in Anomalous Sites of Piedmont, Italy
Authors: Magnoni M. , Tofani S.
Published: February 2017

This laboratory, responsible for the monitoring of radon environmental pollution in the Piedmont Region (total area 25,400 km2, population (4.5 million), decided to promote surveys in areas where the presence of high radon concentrations is expected. Indoor radon concentrations in houses in the village of Peveragno (CN) were studied. Peveragno is a small centre (400 inhabitants) in the western Alps where there was a uranium mine until the 1960s and where many water sources and wells with a high radon content were found. The measurement techniques employed were based on Kodak LR-115 type II etched track detectors. The number of houses monitored (during summer 1992) was 86, distributed throughout the Peveragno municipality. Usually, two dosimeters were employed for each house, one in the lower floor, the other in the higher. In special cases cellars were also measured. The radon content in public water supplies was also measured. High radon levels were found in many cases: about 13% of all houses monitored showed concentrations above the Reference Level of 400 Bq.m-3, with a maximum of over 24000 Bq.m-3. The results are presented and discussed.
Dosimetry of Non-Ionising Radiation
Authors: Oberhofer (INVITED) M.
Published: February 2017

The increasing application of non-ionising radiations, such as radio- and microwaves, ultrasound, lasers and ultraviolet radiation, for example, requires more and more attention with regard to the dangers associated with their use. For this purpose studies are being performed on an increasing scale which correlate energy fluxes and/or absorption and temperature increases with biological effects. Techniques similar to the dosimetric methods in the field of ionising radiation are being developed which allow exposure limits to be measured. In some instances solid state detectors are utilised. An attempt is made to summarise worldwide efforts to measure non-ionising radiation quantitatively and to develop 'dosimetric' methods.
Estimation of TL Response of Phosphors to Beta Rays by Measuring Energy Spectrum of Absorbed Beta Particles
Authors: Koshijima T. , Nakajima T.
Published: February 2017

The beta energy absorbed in the thermoluminescent (TL) phosphor was determined directly from the difference in the pulse height spectrum between incident and transmitted beta particles to and from the phosphor, in order to examine the sensitivity of commercially available powdered phosphors, LiF (TLD-100) and CaF2:Dy (TLD-200), to beta particles. A beta ray spectrometer equipped with plastic scintillator and GM tube was used, instead of an extrapolation chamber. The TL sensitivity of LiF powder to the beta particles emitted from sources of 45Ca, 204Tl, 90Sr/90Y, and 32P was found to be 0.18-0.22 Gy.µJ-1 per 5 mg of phosphor expressed in equivalent air kerma of 60Co gamma rays. The sensivity of CaF2:Dy powder to beta rays was approximately 8 times that of LiF. It is suggested that a beta dosemeter capable of estimating the beta energy or a two-element or multi-element dosemeter is necessary for measurement of beta dose in a deep skin.
Some Parameters of Low and High LET Radiation Dosimetry Using CaF2:Tm TLDs
Authors: Pradhan A.S. , Bhatt R.C.
Published: February 2017

The ratio of heights of two major glow peaks (150 oC and 240 oC) in CaF2:Tm varies significantly with the gamma ray dose above 10 Gy, with the energy of photons for doses below 10 Gy, and with the LET of charged particles. The change in peak height ratio can be used for high-level gamma ray dosimetry in the range from 10 Gy to 3 x 103 Gy, and beyond 3 x 103 Gy the change in colour itself becomes an indication of high-level irradiation. For dosimetry in the mixed fields of low and high LET radiations, extreme care has to be taken that the contribution due to the photons of energy below 200 keV is kept negligible. For high LET and fast neutron dosimetry the dose due to the gamma ray component should be a small fraction of the total dose.
Recent Advances in Thermoluminescence Dating
Authors: Aitken (INVITED) M.J.
Published: February 2017

Initially application was to ancient pottery and other baked clay, detection of forgeries in art ceramics having a particularly powerful impact. In recent years there has been a growing extension of TL into non-pottery materials. Heated flints from paleolithic fire-places is one application. Another is in the dating of igneous rocks from recent volcanic events; formerly this had been impossible on account of the malign phenomenon of non-thermal ('anomalous') fading exhibited by volcanic minerals but this is now being circumvented by utilising TL in the 600 oC region of the glow curve. TL dating has also been extended to unburnt calcite, one application being stalagmitic floors in paleolithic caves. Another recent development is the use of TL for dating aeolian sediment and some types of waterborne sediment. These developments give prospect of establishing a TL-based chronology, both for archaeology and quaternary research, extending back well beyond the range of radiocarbon, perhaps reaching a million years ago.
Dose Evaluation at Low Level with TL Dosimetry in the Linac Facility of Osaka University
Authors: Owaki S. , Hayashiuchi Y. , Ohkuma J. , Sawai T. , Okada T. , Kawanishi M.
Published: February 2017

Monthly environmental radiation doses in an accelerator facility were observed with a high sensitivity TLD system at 9 sites in a low background area. The average annual dose varied little from site to site, demonstrating the reliability of the system. However, a change in the environmental dose in the building, from month to month, was found to be large. Because the personnel dose due to accelerator operation is of the same order as the monthly environmental one, the environmental dose was evaluated by a statistical treatment, taking into account sensitivity level shifts of the TLD reader, uniformity and reproducibility of TL elements etc. The value obtained in this way is available to estimate the most probable personnel dose each month, as well as the exact environmental radiation dose.
Characteristics of a New Dosemeter Material: LiF(Mg,Cu,P)
Authors: DeWerd L.A. , Cameron J.R. , Da-Ke Wu , Papini T. , Das I.J.
Published: February 2017

Some of the dosimetric properties of a high sensitivity thermoluminescence dosemeter material, LiF(Mg,Cu,P), are described. This material, prepared at the Chinese Academy of Medical Sciences, has about 23 times higher sensitivity than that of LiF(Mg,Ti). It is stable and reusable without significant loss of sensitivity. The single peak has thermoluminescent emission in the blue region of the spectrum.
Alpha Energy Sensitive Devices for Dosimetric Purposes - Abstract only
Authors: Pai H.L. , Aitken J.H. , Duport P. , Story R.S.
Published: February 2017

This paper compares various approaches which may lead to simple means of obtaining the required energy resolution for dosimetry of alpha emitters occurring in the various stages of the nuclear fuel cycle. The report starts by considering the potential of high resolution etched track devices in view of the data obtained for Kodak pathe LR115 type II detector using alphas from a Van de Graaff accelerator and alpha particle spectroscopy data for CR39 obtained by Fews and Henshaw. Application to dosimetry is then discussed, including simple fast read-out methods such as use of an image analysis system (Artek #982). Three approaches are considered: (1) Absorber method. (2) Individual track light-intensity method. (3) Individual track-size measurement method.
Automatic Method for Evaluating Elapsed Time Between Irradiation and Readout in LiF-TLD
Authors: Moscovitch M.
Published: February 2017

It has been shown that by application of glow curve deconvolution when coupled with the fading properties of Peak 2 and Peak 3 integrals in LiF:Mg,Ti, it is possible to measure the time since irradiation to within 10%. An automatic peak search technique identifies the various glow peaks and provides the initial parameters required by the deconvolution program. Fading studies utilising this technique were made on LiF samples during a period of three months in which the time between irradiation and readout was systematically varied. These studies demonstrate that the ratio of the area of Peak 2 to that of Peak 5 can be used to estimate elapsed time up to 100 hours. The ratio of Peak 3 to Peak 5 integrals extends the elapsed time interval to at least three months. During this period of time, some gradual reduction in the relative intensity of the Peak 4 integral has been also observed.
ESR Dosimetry of A-Bomb Radiation Using Tooth Enamel and Granite Rocks
Authors: Ikeya M. , Miki T. , Kai A. , Hoshi M.
Published: February 2017

The A-bomb radiation dose of survivors at different distances from the centre of the A-bomb explosion has been determined using electron spin resonance (ESR) of their tooth enamel and compared with the tentative dose revised in 1985 considering shielding factors. A trial to determine A-bomb dose has been made using Ge and E' centre signals of quartz grains in the building wall and bridge pillar granite close to the hypocentre of the A-bomb at Hiroshima.
A TLD Reader System Upgrade Conversion to Microprocessor Technology
Authors: Bradley R.P. , Grogan D.
Published: February 2017

Since the conversion from film dosemeters to thermoluminescence dosemeters in 1976, the national monitoring programme operated by the Bureau of Radiation and Medical Devices, Department of National Health and Welfare, Canada, has used three readers of the type designed by the Chalk River Nuclear Laboratories. The question of replacing or updating this equipment was raised late in 1984 and a decision to upgrade by an electronic conversion method was made. This approach had already been used successfully in developing a fourth reader and dosemeter for the uranium mining and milling industry. Using the experience and confidence gained through this exercise, a more sophisticated microprocessor-based electronics package was designed. The microprocessor used was the model LC-3 manufactured by Cybernex of Ottawa, Canada and represented a significant increase in computational ability and speed over the previous choice of the LC-1. Once the conversion is completed, the readers, previously interfaced to and controlled by a Hewlett Packard HP-3000 minicomputer, will be stand-alone units. Full graphics capability, digitised glow curves and extensive monitoring of the system functions will be available. Details of the impact this will have on the operation and reliability aspects of the system are presented.
Review of the Principal Materials Available for Thermoluminescent Dosimetry
Authors: Portal (INVITED) G.
Published: February 2017

A chronological history of the thermoluminescent materials most commonly used for radiation dosimetry is presented. The evolution of their dosimetric and physical properties is analysed and compared. Conclusions are drawn on the way in which the characteristics of these products could be improved for the different fields of application envisaged.
Magnesium Borate in TL Dosimetry
Authors: Prokic M.
Published: February 2017

The dosimetric performances of improved magnesium borate TL dosemeters have been evaluated under operational conditions and the results are presented. The wide range of application of this type of dosemeter for different radiation protection purposes is also presented.
Investigation of Phosphorescence Decay Using TL-like Presentation
Authors: Chen R. , Kristianpoller N.
Published: February 2017

The phosphorescence decay of radiation stimulated luminescent materials at a constant temperature reveals information on the processes involved. The shape of the decay curve depends on the kinetics. Inversely, a study of these curves yields information on the kinetic parameters. A way of presenting the phosphorescence decay which emphasises the features of the curve is to plot y=t(I(t) as a function of x=In t. This yields a peak shaped curve for a simple phosphorescence decay. This curve resembles the TL glow curve that one expects for the same kinetic law. In the present work, the shape of the curve is studied by checking the symmetry factor µg=d/? where d=x2-xm, ?=x2-x1 and where xm is the maximum point and x1, x2 are the two half-intensity points. The dependence of µg on the kinetic order b is determined. Inversely, the parameter b can be evaluated from the experimental results.
Predicting the Rate of 222Rn Entry from Soil into the Basement of a Dwelling Due to Pressure-Driven Air Flow
Authors: Nazaroff W.W.
Published: February 2017

A combination of analytical and numerical methods is applied to the problem of computing 222Rn transport from soil into a dwelling having a basement. Transport is assumed to occur solely by pressure-driven air flow, and the basement shell is assumed to have a single dominant leak that is uniformly distributed around the perimeter at the level of the floor. The results show that for small flow rates of air through the soil, the radon entry rate into the basement increases in proportion to ?Po, the outdoor-indoor pressure difference at the soil level. For large flow rates, the entry rate increases only in proportion to ?Po2/3, due to depletion of radon concentration in the soil. A sample calculation indicates that via this transport mode, soil having ordinary 226Ra content and moderately high permeability can be responsible for indoor radon concentrations of the order of 500 Bq.m-3, greater than recommended guidelines for new housing.
The Radial Dose Distribution as a Microdosimetric Tool
Authors: Varma M.N. , Zaider M.
Published: February 2017

We examine, as a function of a particle type and energy as well as the geometrical configuration of the sensitive site, the extent to which a description of the track in terms of itsradial dose distribution can be used as a substitute for a full microdosimetric description. The critical parameter appears to be the ratio between the site diameter and the maximum lateral extension of the track (penumbra): whenever this ratio is significantly larger than 1 the radial-distribution-derived microdosimetric spectrum is accurate. While in general, for ratios smaller than 1, the spectra thus calculated are not correct, one can obtain significant improvement by considering tracks of restricted radial extent (yet comprising most of the delivered dose). In terms of a microdosimetric-based quality factor the radial dose distributions generally lead to correct estimates.
Further Development of the Variance-Covariance Method
Authors: Chen J. , Brekow J. , Roos H. , Kellerer A.M.
Published: February 2017

Applications of the variance-covariance technique are presented that illustrate the potential of the method. The dose mean lineal energy, yD, can be determined in time-varying radiation fields where the fluctuations of the dose rate are substantially in excess of the stochastic fluctuations of the energy imparted. An added advantage is, that yD is little influenced by noise that affects both detectors simultaneously. The variance-covariance method is thus stable with respect to dose rate fluctuations and other temporal variations of a radiation field, and to various influences of noise and electronic artefacts. The dose mean lineal energy obtained at different simulated diameters agrees well with experimental data by other authors and can be determined for small simulated diameters (below 100 nm).
Studying Low Dose Effects Using Single Particle Microbeam Irradiation
Authors: Braby L.A. , Reece W.D.
Published: February 2017

Our current understanding of the effects of low doses of ionising radiation relies on extrapolation from doses which are orders of magnitude larger than those resulting from environmental or occupational exposure. This has been necessary, in part, because the stochastic nature of energy deposition by charged particle tracks makes it difficult to measure effects at low doses. At low doses test populations consist primarily of unirradiated cells, with a few cells which have been traversed by one track and a very small fraction which have been traversed by two or more tracks. Furthermore, the position of tracks relative to critical structures in the cells are random, resulting in large variations in the probability of an effect from one irradiated cell to another. These limitations on the study of the relationship between energy deposited in the cell and the biological effect can be largely eliminated by irradiating individual cells with a counted number of monoenergetic charged particles collimated so that they traverse specific target structures.
Current Status of Ultrasoft X Rays and Track Structure Analysis as Tools for Testing and Developing Biophysical Models of Radiation Action
Authors: Goodhead D.T. , Nikjoo H.
Published: February 2017

Ultrasoft X rays have provided a valuable tool to probe subcellular mechanisms of radiation action. Sufficient data have become available to allow meaningful comparisons between laboratories and between biological assays. A brief summary is given of these data. They show that there is generally good agreement between the results from different laboratories but that there are apparently major differences in RBE between cell types which do not conform to simple expectations or explanations. This raises an intriguing conundrum which awaits satisfactory solution. The solution should provide valuable additional insight into the subcellular mechanisms, including information on spatial distributions of critical subcellular target material and/or essential difference between the responses of different cell types. A variety of potential solutions to the conundrum are discussed and it is shown how Monte Carlo track structure analyses allow some of these to be studied in terms of properties of radiation tracks over nanometre dimensions.
The Role of Microdosimetry in the Understanding of Radiation Quality
Authors: Rossi (INVITED) H.H.
Published: February 2017

A recent report of the International Commission on Radiation Units and Measurements (ICRU) proposes various changes in the formulation of the quality factor (Q) in radiation protection. The recommendations are considered to be generally consistent with microdosimetric considerations and radiobiological findings. The principal inconsistency, which is based on technical limitations, relates Q to lineal energy in 1 micrometre sites rather than in more appropriate much smaller ones. However, the practical consequences seem acceptable in view of other, larger, uncertainties in radiation protection.
Dissolution Glow Curve in LLD
Authors: Haverkamp U. , Wiezorek C. , Pötter R.
Published: February 2017

Lyoluminescence dosimetry is based upon light emission during dissolution of previously irradiated dosimetric materials. The lyoluminescence signal is expressed in the dissolution glow curve. These curves begin, depending on the dissolution system, with a high peak followed by an exponentially decreasing intensity. System parameters that influence the graph of the dissolution glow curve, are, for example, injection speed, temperature and pH value of the solution and the design of the dissolution cell. The initial peak does not significantly correlate with the absorbed dose, it is mainly an effect of the injection. The decay of the curve consists of two exponential components: one fast and one slow. The components depend on the absorbed dose and the dosimetric materials used. In particular, the slow component correlates with the absorbed dose. In contrast to the fast component the argument of the exponential function of the slow component is independent of the dosimetric materials investigated: trehalose, glucose and mannitol. The maximum value, following the peak of the curve, and the integral light output are a measure of the absorbed dose. The reason for the different light outputs of various dosimetric materials after irradiation with the same dose is the differing solubility. The character of the dissolution glow curves is the same following irradiation with photons, electrons or neutrons.
Study of the Annealing Characteristics of LiF:Mg,Ti Using Computerised Glow Curve Deconvolution
Authors: Horowitz Y.S.
Published: February 2017

Computerised glow curve deconvolution (CGCD) based on first order TL kinetics has been used to study the dependence of the TL sensitivity, S, of glow peaks 2, 3 and (4+5) on choice of annealing temperature during the low and high temperature annealing procedures commonly applied to LiF:Mg,Ti (TLD-100, Harshaw/Filtrol). This was in order to determine optimal temperatures for these procedures as well as to investigate the role of annealing temperature reproducibility in the requirements of high precision TL dosimetry. The recommended optimum annealing procedure is: (i) 400 oC, for 1 h followed by an accelerated 'natural' cooling rate of approximately 150 oC. min-1. (ii) 75 ± 3 oC, 24 h pre-irradiation and/or 100 oC, 10 min post-irradiation.
Comparison of the Responses of Several TLDs to Various Radionuclides
Authors: Vekic B. , Ranogajec-Komor M. , Cukman M.
Published: February 2017

The TL responses of TLD-700, LiF:Mg,Ti, MgB4O7:Dy, CaF2:Mn and Al2O3:Mg,Y dosemeters were calibrated against the radiation of 99Tcm (140 keV) and 131I (80-723 keV) in addition to calibration with 226Ra (0.093-2.45 MeV) and 137Cs (0.66 MeV) sources. 99Tcm and 131I are the most commonly used radionuclides in nuclear medicine. According to our previous energy response studies involving X ray irradiations, the TL response of TLD-700, LiF:Mg,Ti and MgB4O7:Dy exhibit low energy dependence. The agreement between the calculated dose and the dose measured by these TLDs is satisfactory, especially in the case of the 131I source. CaF2:Mn and Al2O3:Mg,Y detectors require special encapsulation for use in the dosimetry of photons in the low energy region.
Modified Track Structure Calculation of Thermoluminescent Yields to Heavy Charged Particles
Authors: Chernov V.G. , Rogalev B.I.
Published: February 2017

Tracks of heavy charged particles are presented as a combination of uniform elementary excitation (so called spurs) with fixed volume and dose. An expression for the calculation of HCP track efficiency relative to gamma efficiency was derived. This expression was used to calculate the relative efficiency of an LiF:Mg, Ti detector to HCPs with energies from 0.01 to 1000 MeV per nucleon. The calculations were found to be in good agreement with the experimental data.
Ultrasound imaging velocimetry with interleaved images for improved pulsatile arterial flow measurements: a new correction method, experimental and
in vivo
validation
Authors: Fraser Katharine H. , Poelma Christian , Zhou Bin , Bazigou Eleni , Tang Meng-Xing , Weinberg Peter D.
Published: February 2017

Blood velocity measurements are important in physiological science and clinical diagnosis. Doppler ultrasound is the most commonly used method but can only measure one velocity component. Ultrasound imaging velocimetry (UIV) is a promising technique capable of measuring two velocity components; however, there is a limit on the maximum velocity that can be measured with conventional hardware which results from the way images are acquired by sweeping the ultrasound beam across the field of view. Interleaved UIV is an extension of UIV in which two image frames are acquired concurrently, allowing the effective interframe separation time to be reduced and therefore increasing the maximum velocity that can be measured. The sweeping of the ultrasound beam across the image results in a systematic error which must be corrected: in this work, we derived and implemented a new velocity correction method which accounts for acceleration of the scatterers. We then, for the first time, assessed the performance of interleaved UIV for measuring pulsatile arterial velocities by measuring flows in phantoms and
in vivo
and comparing the results with spectral Doppler ultrasound and transit-time flow probe data. The velocity and flow rate in the phantom agreed within 5–10% of peak velocity, and 2–9% of peak flow, respectively, and
in vivo
the velocity difference was 9% of peak velocity. The maximum velocity measured was 1.8 m s
−1
, the highest velocity reported with UIV. This will allow flows in diseased arteries to be investigated and so has the potential to increase diagnostic accuracy and enable new vascular research.
Cooperators trade off ecological resilience and evolutionary stability in public goods games
Authors: Rauch Joseph , Kondev Jane , Sanchez Alvaro
Published: February 2017

Microbial populations often rely on the cooperative production of extracellular ‘public goods’ molecules. The cooperative nature of public good production may lead to minimum viable population sizes, below which populations collapse. In addition, ‘cooperator’ public goods producing individuals face evolutionary competition from non-producing mutants, or ‘freeloaders’. Thus, public goods cooperators should be resilient not only to the invasion of freeloaders, but also to ecological perturbations that may push their populations below a sustainable threshold. Through a mathematical analysis of the Ecological Public Goods Game, we show that game parameters that improve the cooperating population's stability to freeloader invasion also lead to a low ecological resilience. Complex regulatory strategies mimicking those used by microbes in nature may allow cooperators to beat this trade-off and become evolutionarily stable to invading freeloaders while at the same time maximizing their ecological resilience. Our results thus identify the coupling between resilience to evolutionary and ecological challenges as a key factor for the long-term viability of public goods cooperators.
The Notch pathway in the annelidPlatynereis: insights into chaetogenesis and neurogenesis processes
Authors: Gazave Eve , Lemaître Quentin I. B. , Balavoine Guillaume
Published: February 2017

Notch is a key signalling pathway playing multiple and varied functions during development. Notch regulates the selection of cells with a neurogenic fate and maintains a pool of yet uncommitted precursors through lateral inhibition, both in insects and in vertebrates. Here, we explore the functions of Notch in the annelidPlatynereis dumerilii(Lophotrochozoa). Conserved components of the pathway are identified and a scenario for their evolution in metazoans is proposed. Unexpectedly, neitherNotchnor its ligands are expressed in the neurogenic epithelia of the larva at the time when massive neurogenesis begins. Using chemical inhibitors and neural markers, we demonstrate that Notch plays no major role in the general neurogenesis of larvae. Instead, we find Notch components expressed in nascent chaetal sacs, the organs that produce the annelid bristles. Impairing Notch signalling induces defects in chaetal sac formation, abnormalities in chaetae producing cells and a change of identity of chaeta growth accessory cells. This is the first bilaterian species in which the early neurogenesis processes appear to occur without a major involvement of the Notch pathway. Instead, Notch is co-opted to pattern annelid-specific organs, likely through a lateral inhibition process. These features reinforce the view that Notch signalling has been recruited multiple times in evolution due to its remarkable ‘toolkit’ nature.
Analysis of dispersion and absorption characteristics of shear waves in sinusoidally corrugated elastic medium with void pores
Authors: Pandit Deepak Kr. , Kundu Santimoy , Gupta Shishir
Published: February 2017

This theoretical work reports the dispersion and absorption characteristics of horizontally polarized shear wave (SH-wave) in a corrugated medium with void pores sandwiched between two dissimilar half-spaces. The dispersion and absorption equations have been derived in a closed form using the method of separation of variables. It has been established that there are two different kinds of wavefronts propagating in the proposed media. One of the wavefronts depends on the modulus of rigidity of elastic matrix of the medium and satisfies the dispersion equation of SH-waves. The second wavefront depends on the changes in volume fraction of the pores. Numerical computation of the obtained relations has been performed and the results are depicted graphically. The influence of corrugation, sandiness on the phase velocity and the damped velocity of SH-wave has been studied extensively.
Earliest filter-feeding pterosaur from the Jurassic of China and ecological evolution of Pterodactyloidea
Authors: Zhou Chang-Fu , Gao Ke-Qin , Yi Hongyu , Xue Jinzhuang , Li Quanguo , Fox Richard C.
Published: February 2017

Pterosaurs were a unique clade of flying reptiles that were contemporaries of dinosaurs in Mesozoic ecosystems. The Pterodactyloidea as the most species-diverse group of pterosaurs dominated the sky during Cretaceous time, but earlier phases of their evolution remain poorly known. Here, we describe a 160 Ma filter-feeding pterosaur from western Liaoning, China, representing the geologically oldest record of the Ctenochasmatidae, a group of exclusive filter feeders characterized by an elongated snout and numerous fine teeth. The new pterosaur took the lead of a major ecological transition in pterosaur evolution from fish-catching to filter-feeding adaptation, prior to the Tithonian (145–152 Ma) diversification of the Ctenochasmatidae. Our research shows that the rise of ctenochasmatid pterosaurs was followed by the burst of eco-morphological divergence of other pterodactyloid clades, which involved a wide range of feeding adaptations that considerably altered the terrestrial ecosystems of the Cretaceous world.
Ultrasound elicits behavioral responses through mechanical effects on neurons and ion channels in a simple nervous system
Authors: Kubanek Jan , Shukla Poojan , Das Alakananda , Baccus Stephen A. , Goodman Miriam B.
Published: February 2017

Focused ultrasound has been shown to stimulate excitable cells, but the biophysical mechanisms behind this phenomenon remain poorly understood. To provide additional insight, we devised a behavioral-genetic assay applied to the well-characterized nervous system ofC. elegansnematodes. We found that pulsed ultrasound elicits robust reversal behavior in wild-type animals in a pressure-, duration-, and pulse protocol-dependent manner. Responses were preserved in mutants unable to sense thermal fluctuations and absent in mutants lacking neurons required for mechanosensation. Additionally, we found that the worm‘s response to ultrasound pulses rests on the expression of MEC-4, a DEG/ENaC/ASIC ion channel required for touch sensation. Consistent with prior studies of MEC-4-dependent currentsin vivo, the worm’s response was optimal for pulses repeated 300 to 1000 times per second. Based on these findings, we conclude that mechanical, rather than thermal stimulation accounts for behavioral responses. Further, we propose that acoustic radiation force governs the response to ultrasound in a manner that depends on the touch receptor neurons and MEC-4-dependent ion channels. Our findings illuminate a complete pathway of ultrasound action, from the forces generated by propagating ultrasound to an activation of a specific ion channel. The findings further highlight the importance of optimizing ultrasound pulsing protocols when stimulating neurons via ion channels with mechanosensitive properties.

Significance Statement

How ultrasound influences neurons and other excitable cells has remained a mystery for decades. Although it is widely understood that ultrasound can heat tissues and induce mechanical strain, whether or not neuronal activation depends on heat, mechanical force, or both physical factors is not known. We harnessedC. elegansnematodes and their extraordinary sensitivity to thermal and mechanical stimuli to address this question. Whereas thermosensory mutants respond to ultrasound similar to wild-type animals, mechanosensory mutants were insensitive to ultrasound stimulation. Additionally, stimulus parameters that accentuate mechanical effects were more effective than those producing more heat. These findings highlight a mechanical nature of the effect of ultrasound on neurons and suggest specific ways to optimize stimulation protocols in specific tissues.
Bootstrap Distillation: Non-parametric Internal Validation of GWAS Results by Subgroup Resampling
Authors: Eccles David A. , Lea Rodney A. , Chambers Geoffrey K.
Published: February 2017

Genome-wide Association Studies are carried out on a large number of genetic variants in a large number of people, allowing the detection of small genetic effects that are associated with a trait. Natural variation of genotypes within populations means that any particular sample from the population may not represent the true genotype frequencies within that population. This may lead to the observation of marker-disease associations when no such association exists.

A bootstrap population sub-sampling technique can reduce the influence of allele frequency variation in producing false-positive results for particular samplings of the population. In order to utilise bioinformatics in the service of a serious disease, this sub-sampling method has been applied to the Type 1 Diabetes dataset from the Wellcome Trust Case Control Consortium in order to evaluate its effectiveness.

While previous literature on Type 1 Diabetes has identified some DNA variants that are associated with the disease, these variants are not informative for distinguishing between disease cases and controls using genetic information alone (AUC=0.7284). Population sub-sampling filtered out noise from genome-wide association data, and increased the chance of finding useful associative signals. Subsequent filtering based on marker linkage and testing of marker sets of different sizes produced a 5-SNP signature set of markers for Type 1 Diabetes. The group-specific markers used in this set, primarily from the HLA region on chromosome 6, are considerably more informative than previously known associated variants for predicting T1D phenotype from genetic data (AUC=0.8395). Given this predictive quality, the signature set may be useful alone as a screening test, and would be particularly useful in combination with other clinical cofactors for Type 1 Diabetes risk.
Gastruloidsdevelop the three body axes in the absence of extraembryonic tissues and spatially localised signalling
Authors: Turner D.A. , Alonso-Crisostomo L. , Girgin M. , Baillie-Johnson P. , Glodowski C. R. , Hayward P. C. , Collignon J. , Gustavsen C. , Serup P. , Steventon B. , Lutolf M. , Martinez Arias A.
Published: February 2017

Establishment of the three body axes is a critical step during animal development. In mammals, genetic studies have shown that a combination of precisely deployed signals from extraembryonic tissues position the anteroposterior axis (AP) within the embryo and lead to the emergence of the dorsoventral (DV) and left-right (LR) axes. We have usedGastruloids, embryonic organoids, as a model system to understand this process and find that they are able to develop AP, DV and LR axes as well as to undergo axial elongation in a manner that mirror embryos. TheGastruloidscan be grown for 160 hours and form derivatives from ectoderm, mesoderm and endoderm. We focus on the AP axis and show that in theGastruloidsthis axis is registered in the expression of T/Bra at one pole that corresponds to the tip of the elongation. We find that localisation of T/Bra expression depends on the combined activities of Wnt/β-Catenin and Nodal/Smad2,3 signalling, and that BMP signalling is dispensable for this process. Furthermore, AP axis specification occurs in the absence of both extraembryonic tissues and of localised sources of signalling. Our experiments show that Nodal, together with Wnt/β-Catenin signalling, is essential for the expression of T/Bra but that Wnt signalling has a separable activity in the elongation of the axis. The results lead us to suggest that, in the embryo, the role of the extraembryonic tissues might not be to induce the axes but to bias an intrinsic ability of the embryo to break its initial symmetry and organise its axes.

One sentence summary

Culture of aggregates of defined number of Embryonic Stem cells leads to self-organised embryo-like structures which, in the absence of localised signalling from extra embryonic tissues and under the autonomous influence of Wnt and Nodal signalling, develop the three main axes of the body.
NMDAR hypofunction increases top-down influence on sensory processing
Authors: Ranson Adam , Broom Eluned , Powell Anna , Hall Jeremy
Published: February 2017

Converging evidence implicates NMDAR disruption in the pathogenesis of schizophrenia, a condition in which perceptual disturbances are prominent. To explore how NMDAR hypofunction causes perceptual symptoms we investigated activity in cortical sensory circuits in awake behaving mice during pharmacologically induced NMDAR hypofunction. We observed a reduction in sensory-driven activity in V1 while input from the anterior cingulate cortex simultaneously increased, suggesting NMDAR hypofunction may lead to altered perception by modifying the balance of top-down and bottom-up processing.
Engaging narratives evoke similar neural activity and lead to similar time perception
Authors: Cohen Samantha , Henin Simon , Parra Lucas C.
Published: February 2017

It is said that we lose track of time - that “time flies” - when we are engrossed in a story. How does engagement with the story cause this distorted perception of time, and what are its neural correlates? People commit both time and attentional resources to an engaging stimulus. For narrative videos, attentional engagement can be represented as the level of similarity between the electroencephalographic responses of different viewers. Here we show that this measure of neural engagement predicted the duration of time that viewers were willing to commit to narrative videos. Contrary to popular wisdom, engagement did not distort the average perception of time duration. Rather, more similar brain responses resulted in a more uniform perception of time across viewers. These findings suggest that by capturing the attention of an audience, narrative videos bring both neural processing and the subjective perception of time into synchrony.
Small-Scale Immunoprecipitation from Fission Yeast Cell Extracts
Authors: Grallert Agnes , Hagan Iain M.
Published: February 2017

We describe procedures for the immunoprecipitation (IP) of a molecule of interest from cell extracts under native or denaturing conditions. The methods are equally effective with antibodies that directly recognize the molecule of interest and those that recognize a generic peptide “epitope tag” that has been fused to sequences encoding the gene of interest. The diverse chemistry of intermolecular interactions and enzymatic activities means that a range of different buffer conditions must be assessed empirically to identify optimal conditions for the study of a specific target/complex in a particular assay. We describe three buffers that can serve as starting points for this empirical testing and discuss modifications that are commonly used in the optimization of assays based on immunoprecipitation.
Neutron and X-ray investigations of the Jahn–Teller switch in partially deuterated ammonium copper Tutton salt, (NH4)2[Cu(H2O)6](SO4)2
Authors: Jørgensen Mads R. V. , Piccoli Paula M. B. , Hathwar Venkatesha R. , Wang Xiaoping , Hoffmann Christina M. , Yakovenko Andrey A. , Halder Gregory J. , Schlueter John A. , Iversen Bo B. , Schultz Arthur J.
Published: February 2017

The structural phase transition accompanied by a Jahn–Teller switch has been studied over a range of H/D ratios in (NH4)2[Cu(H2O)6](SO4)2 (ACTS). In particular, single-crystal neutron diffraction investigations of crystals with deuteration in the range 50 to 82% are shown to be consistent with previous electron paramagnetic resonance (EPR) experiments exhibiting a phase boundary at 50% deuteration under ambient pressure. Polycrystalline samples show that the two phases can co-exist. In addition, single-crystal neutron and polycrystalline X-ray diffraction pressure experiments show a shift to lower pressure at 60% deuteration versus previous measurements at 100% deuteration.