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Although high-sensitivity liquid scintillation (LS) spectroscopy is theoretically capable of producing finite radiocarbon ages in the 50,000- to 70,000-yr range, there is little evidence in the literature that meaningful dates in this time period have been obtained. The pressing need to undertake calibration beyond 26 kyr has resulted in the regular publication of 14C results in excess of 50 kyr, yet very little effort has been made to demonstrate their accuracy or precision. There is a paucity of systematic studies of the techniques required to produce reliable dates close to background and the methods needed to assess contamination from either in situ sources or laboratory handling and processing. We have studied the requirements for producing accurate and reliable dates beyond 50 kyr. Laboratory procedures include optimization of LS spectrometers to obtain low and stable non-14C background count rates, use of low-background counting vials, large benzene volumes, long counting times, and preconditioning of vacuum lines. We also discuss the need for multiple analyses of a suitable material containing no original 14C (background blank) and the application of an appropriate statistical model to compensate for variability in background contamination beyond counting statistics. Accurate and reproducible finite ages >60 kyr are indeed possible by high-sensitivity LS spectroscopy, but require corroborating background blank data to be defensible.
It is well known that radiocarbon years do not directly equate to calendar time. As a result, considerable effort has been devoted to generating a decadally resolved calibration curve for the Holocene and latter part of the last termination. A calibration curve that can be unambiguously attributed to changes in atmospheric 14C content has not, however, been generated beyond 26 kyr cal BP, despite the urgent need to rigorously test climatic, environmental, and archaeological models. Here, we discuss the potential of New Zealand kauri (Agathis australis) to define the structure of the 14C calibration curve using annually resolved tree rings and thereby provide an absolute measure of atmospheric 14C. We report bidecadally sampled 14C measurements obtained from a floating 1050-yr chronology, demonstrating repeatable 14C measurements near the present limits of the dating method. The results indicate that considerable scope exists for a high-resolution 14C calibration curve back through OIS-3 using subfossil wood from this source.
Objectives: One of the most prominent features of schizophrenia is relatively lower general cognitive ability (GCA). An emerging approach to understanding the roots of variation in GCA relies on network properties of the brain. In this multi-center study, we determined global characteristics of brain networks using graph theory and related these to GCA in healthy controls and individuals with schizophrenia. Methods: Participants (N=116 controls, 80 patients with schizophrenia) were recruited from four sites. GCA was represented by the first principal component of a large battery of neurocognitive tests. Graph metrics were derived from diffusion-weighted imaging. Results: The global metrics of longer characteristic path length and reduced overall connectivity predicted lower GCA across groups, and group differences were noted for both variables. Measures of clustering, efficiency, and modularity did not differ across groups or predict GCA. Follow-up analyses investigated three topological types of connectivity—connections among high degree “rich club” nodes, “feeder” connections to these rich club nodes, and “local” connections not involving the rich club. Rich club and local connectivity predicted performance across groups. In a subsample (N=101 controls, 56 patients), a genetic measure reflecting mutation load, based on rare copy number deletions, was associated with longer characteristic path length. Conclusions: Results highlight the importance of characteristic path lengths and rich club connectivity for GCA and provide no evidence for group differences in the relationships between graph metrics and GCA. (JINS, 2016, 22, 240–249)
We have analysed observations of the interstellar extinction in the range 3400 Å–l 1000 Å. The observations have high photometric accuracy and wavelength resolution, and allow a detailed examination of broadband structure as well as the general shape of the wavelength dependence of the extinction curve. The broadband structure has a characteristic size of several hundred ångströms, and may be as important as the diffuse bands in indicating the physical nature of the grains.
We describe our preliminary theoretical interpretation of this broadband structure, and the new observation which it predicts.
The beneficial mechanical properties of segmented polyurethanes derive from microphase separation of immiscible hard and soft segment-rich domains at room temperature. We are interested in the structure of the domains, how these are affected by hydrolytic aging, and how the structure is modified by low molecular weight plasticizers. To assessed the distribution of the plasticizer in polyurethane, we did small-angle neutron scattering measurements on mixtures of 23% hard segment poly(esterurethane) with different amounts of either non-deuterated or deuterated plasticizer. We analyzed the results using a simple model in which the contrast, Δ=H-, between the hard and soft segment-rich domains is varied by the amount of deuterated or hydrogenated plasticizer, using the fact that I(Q) ∼ Δ2. The result demonstrated that the plasticizer is largely associated with the soft segment rich domains. The structure of PESU with the chain extender of the hard segment was assessed after aging under hydrolytic conditions. The results show that the microphase structure coarsens and segregates and that the hard and soft segments segregated as a result of the loss of constraints from hydrolytic soft segment chain scission. The results on plasticizer distribution and the effects of hydrolytic aging give insight on the loss of mechanical properties that occur in each case.
Erbium(III) doped TiO2 nanofibers (Er2Ti2O7) have been synthesized by electrospinning mixtures of polymers, metal-containing materials, and erbium acetate. These electrospun nanofibers were subsequently annealed at temperatures of 550, 750, 950, and 1150 oC to remove the organics and leave behind the metal oxides. The crystal structure and optical properties of the nanofiber pyrochlores were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transformation IR (FTIR) spectroscopy. Different crystal structures were formed by controlling the annealing conditions. XRD data are compared with near-IR spectra to better understand the effects of annealing temperature on the Er (III) thermally-excited selective optical emission process.
Swan, Ganz and colleagues were the first to describe the use of a flow-directed, balloon-tipped catheter for the catheterization of the right heart and the pulmonary artery (PA) in 1970. Since then, the PA catheter (PAC) has become a widespread monitoring tool in the management of critically ill patients. Its use necessitates profound knowledge of cardiovascular (patho)-physiology and exhaustive information on current evidence guiding patient selection, particularly in the light of ongoing controversy on its safety and efficacy.
The pulmonary artery catheter
The commonly used PAC has a circumference of 7.0, 7.5 or 8.0 French and is 110 cm long with distances marked at 10-cm intervals. The standard PAC contains four separate internal lumens.
Distal lumen and proximal lumen
These lumen lead to the distal port at the tip of the catheter and to a second port approximately 30 cm proximally to the catheter tip. The distal lumen is used to measure PA pressure (PAP) and sample mixed venous blood, whereas the proximal lumen serves to measure central venous pressure (CVP).
This lumen leads to a balloon just proximal to the catheter tip. Inflating the balloon enables placement of the catheter in the PA and to measure PA occlusion pressure.
The fourth lumen contains wires leading to the temperature thermistor located proximally to the balloon. The thermistor enables measurement of blood temperature for the calculation of cardiac output (CO).
During off-pump coronary bypass grafting, surgical manipulation and dislocation of the heart may cause cardiovascular instability. Monitoring of cardiac output facilitates intraoperative haemodynamic management but pulmonary artery catheters are often considered too invasive. Pulse contour analysis and transoesophageal echocardiography could serve as alternatives, but there is controversy about their accuracies. We validated pulse contour analysis using a standard radial arterial catheter (PulseCO™) and aortic Doppler flowmetry with transoesophageal echocardiography in patients undergoing off-pump coronary bypass surgery. Pulmonary arterial thermodilution served as the reference technique.
In 20 patients undergoing off-pump coronary bypass, cardiac output was measured with bolus thermodilution (COTD), pulse contour analysis (COPC), and transoesophageal echocardiography (COecho) at fixed time intervals during the procedure. Data were compared using linear regression and Bland–Altman analysis. At the end of the procedure, dobutamine was infused at a rate of 2.5 μg kg−1 min−1 in six patients to study the agreement between methods in quantifying changes in cardiac output.
Comparison between COPC and COTD showed a bias ± limits of agreement of −0.03 ± 1.30 L min−1 (mean error 29%). Doppler echocardiography was not always feasible when the heart was displaced from the oesophagus and had lower accuracy: bias ± limits of agreement vs. COTD was 0.45 ± 1.93 (mean error 43%). Increases in cardiac output induced by dobutamine were well quantified both by pulse contour analysis (COPC = 0.76 × COTD + 0.58; r2 = 0.65) and Doppler, although the latter tended to overestimate these changes (COecho = 1.58 × COTD − 0.13; r2 = 0.53).
Calibrated pulse contour analysis using the PulseCO system is an acceptable technique to measure cardiac output non-invasively in off-pump coronary bypass patients. Doppler echocardiography performs less well and is not always feasible with transoesophageal echocardiography when the heart is displaced.
Small-angle scattering (SAS) and ultra small-angle scattering techniques, employing x-rays and neutrons, were used to characterize six different aluminum nanopowders and nanopowders composed of molybdenum trioxide and tungsten trioxide nanoparticles. Each material has different primary particle morphology and aggregate and agglomerate geometry, and each is important to the development of nano-energetic materials. The combination of small-angle and ultra small-angle techniques allowed a wide range of length scales to be probed, providing a more complete characterization of the materials. For the aluminum-based materials, differences in the scattering of x-rays and neutrons from aluminum and aluminum oxide provided sensitivity to the metal core and metal oxide shell structure of the primary nanoparticles. Small-angle scattering was able to discriminate between particle size and shape and agglomerate and aggregate geometry, allowing analysis of both aspects of the structure. Using the results of these analyses and guided by scanning electron microscopy (SEM) images, physical models were developed, allowing for a quantitative determination of particle morphology, mean nanoparticle size, nanoparticle size distribution, surface layer thickness, and aggregate and agglomerate fractal dimension. Particle size distributions calculated using a maximum entropy algorithm or by assuming a log-normal particle size distribution function were comparable. Surface area and density determinations from the small-angle scattering measurements were comparable to those obtained from other, more commonly used analytical techniques: gas sorption using Brunauer–Emmett–Teller analysis, thermogravimetric analysis, and helium pycnometry. Particle size distribution functions derived from the SAS measurements agreed well with those obtained from SEM.
Background and objective: Cardiopulmonary bypass is associated with changes of intra- and extravascular volume status often resulting in cardiopulmonary dysfunction. The purpose of this prospective double-blind study was to evaluate the influence of different priming solutions of the extracorporeal circuit on intra- and extravascular volume status and haemodynamics in patients undergoing elective mitral valve replacement. Methods: Twenty-two patients with mitral valve insufficiency were randomly allocated into two equal groups. In Group 1 cardiopulmonary bypass was primed with a nearly isooncotic solution consisting of 4% albumin. The second group received a pure crystalloid priming solution. The thermo-dye indicator dilution technique was used for the assessment of cardiac output, central and pulmonary blood volume, right ventricular end-diastolic volume and total blood volume. Results: Patients in the crystalloid group showed increased intraoperative fluid requirements. Significantly more fluid was accumulated in the extravascular space whereas total blood volume was decreased after surgery. Stroke volume index (SVI) was significantly decreased in the immediate postoperative period when compared to baseline. As indicated by the increase in extravascular fluid content after surgery, both colloid and crystalloid priming volumes were transferred to the extravascular space. Conclusion: The use of colloid priming solutions in patients with mitral valve insufficiency leads to less fluid requirements and significantly reduced fluid shift in the interstitium. However, these changes are not associated with changes in haemodynamic parameters or short term outcome.
In the Grampian (Ordovician) orogenic belt in northwestern Ireland the Dalradian
Supergroup abuts and interleaves with an enigmatic psammite-dominant unit, with relict latest
Precambrian granulite-facies assemblages, known as the Slishwood Division. These two units were
most likely tectonically juxtaposed during the D3 phase of Dalradian deformation. Using Ar–Ar,
Rb–Sr and Sm–Nd methods, 53 new mineral ages have been obtained from both rock units, and from
pegmatites intruding them, in an attempt to constrain the timing of their juxtaposition and the history
they subsequently shared. Prior to D3 (c. 480 Ma), retrograde hornblende poikiloblasts grew in
granulite-facies metabasite pods within the Slishwood Division. Tectonic juxtaposition (D3) with the
Dalradian is loosely constrained between 479 Ma and 459 Ma but is likely to have occurred between
470 Ma and 459 Ma. Dalradian peak metamorphic conditions were attained shortly after D3, at
around 460 Ma. Extensional collapse of the orogen, with rapid uplift and exhumation, is dated by an
abundance of mineral cooling ages between 460 Ma and 450 Ma. Orogenic collapse is also dated,
more precisely, by widespread pegmatite intrusion into both rock units at about 455 Ma. Initial
87Sr/86Sr ratios suggest that these pegmatites are partial melts from Dalradian metasediments. A
second suite of pegmatites were intruded, along with the Ox Mountains Granodiorite, much later at
or around 400 Ma during sinistral shearing.
We report a U–Pb monazite age of 23.0±0.2 Ma for the Shivling leucogranite, a
tourmaline+muscovite±biotite leucogranite at the top of the High Himalayan slab in the Garhwal
Himalaya, north India. The Shivling–Bhagirathi leucogranite is a viscous near-minimum melt,
emplaced as a foliation parallel laccolith via a dyke network not far from its source region. Prograde
heating occurred soon after the India–Asia collision at c. 50 Ma up to melting at 23 Ma and high
temperatures (>550 °C) were maintained for at least 15 Ma after garnet growth. The leucogranite was
emplaced at mid-crustal depths along the footwall of the Jhala fault, a large-scale low-angle normal
fault, part of the South Tibetan Detachment system, above kyanite and sillimanite grade gneisses. The
geometry of the leucogranite laccolith shows biaxial extension and boudinage both perpendicular
(north-northeast–south-southwest) and parallel to the strike (west-northwest–east-southeast) of the
mountain range. Unroofing occurred by underthrusting beneath the High Himalayan slab along the
Main Central Thrust zone, progressively ‘jacking up’ the leucogranites, removal of material above by
low-angle normal faulting, and erosion. Very rapid cooling at rates of 200–350 °C/Ma between
23–21 Ma immediately followed crystallization, as tectonic unroofing and erosion removed 24–28 km
of overburden during this time. K–Ar muscovite ages are 22±1.0 Ma and fission track ages of zircons
from >5000 m on the North Ridge of Shivling are 14.2±2.1 and 8.8±1.2 Ma and apatites are
3.5±0.79 and 2.61±0.23 Ma. Slow steady state cooling at rates of 20–30 °C/Ma from 20–1 Ma shows
that maximum erosion rates and unroofing of the leucogranite occurred during the early Miocene.
This timing coincides with initiation of low-angle, north-dipping normal faulting along the South
Tibetan Detachment system.
The Coire Dhuinnid fault zone contains emerald green chromian illite-ankerite-quartz rocks that are similar in appearance to the fuchsite(or mariposite)-carbonate-quartz parageneses that are commonplace in Archaean greenstone belts but which are rather rare in Phanerozoic rocks. The chromian illite contains 2.3 wt.% Cr2O3, low K2O (7.1–7.6 wt.%) and high H2O+ (5.7 wt.%), and it is a 1M polytype with ≤10% of an illite/smectite interstratification indicative of a formation temperature of c. 175–200°C. The host rocks contain high concentrations of Ni and Cr, and show low concentrations of Ti, Nb, Y and Zr, suggesting a former primitive mafic protolith (boninitic magma?); they are considered to be retrograde remnants of Lewisian rocks. The latter, and the associated rocks of the Moine Series, have been affected by CO2 metasomatism that was accompanied by the addition of Ca(+Sr), Fe and Mg, and by the removal of Na from, and the addition of H2O to the Moine metasediments. Radiogenic isotope studies of mineral separates and whole rock from sample no. 43 yielded ages of 483±2 Ma (Ar-Ar dating on Cr illite), 413±12 Ma (K-Ar dating on Cr illite), and 322±9 Ma (Rb-Sr dating on minerals and whole rock); the significance of this discrepant pattern is discussed.
The definition of bent is redefined for any finite field. Our main result is a complete description of the relationship between bent polynomials and perfect non-linear functions over finite fields: we show they are equivalent. This result shows that bent polynomials can also be viewed as the generalisation to several variables of the class of polynomials known as planar polynomials. An explicit method for obtaining large sets of not necessarily distinct maximal orthogonal systems using bent polynomials is given and we end with a short discussion on the existence of bent polynomials over finite fields.
The Llanrwst Pb–Zn and Llanfair–Talhaiarn Cu–Pb–Zn orefields contain vein mineralization similar to Lower Palaeozoic-hosted base metal deposits elsewhere in the British Isles, which are believed to have formed in the late Palaeozoic. K–Ar and Rb–Sr data on intensely sericitized wallrock material indicate that the main phase of mineralization at both orefields occurred between the mid-Devonian and theTournasian (386–350 Ma). The latest veins at Llanrwst formed in Visean–Westphalian times. Gangue mineral Sr isotope compositions indicate a mixture of radiogenic wallrock-derived Sr with less radiogenic Sr, with a poorly-defined trend to more radiogenic compositions with time.
The age of the main mineralization precludes dewatering of Carboniferous basins as a source of ore fluid. More generally Sr isotopes rule out unmodified basinal brines or metamorphic fluids as mineralizing agents, since their Sr content would be too radiogenic. Local sources of unradiogenic Sr are available at Llanrwst in metadolerites and calcareous sandstones and at Llanfair–Talhaiarn in thin Ludlow Limestone beds.
Experiments were performed to determine if RAPD profiles developed using total DNA isolated from soybean seed could be affected by the physiological state or the quality of the seed. RAPD profiles were developed using template DNA isolated from a single seed lot of soybean (Glycine max L. cv. Kirby). High quality seeds were used to produce four populations varying in either quality or physiological state: untreated control seed ambient temperature and humidity storage for 12 months, accelerated aging at 41°C and 100% relative humidity for 48 h, and controlled hydration (seed priming). One hundred and eighty-eight primers were used to create separate RAPD profiles from total DNA isolated from each set of seed and from soybean leaf tissue. Sixteen polymorphisms from 14 primers were identified as a result of seed treatments. Six primers showed nine polymorphisms in RAPD profiles of ambient-stored seed DNA, while four and two primers produced polymorphisms in reactions using accelerated aged or primed-seed template DNA, respectively. Two primers showed a polymorphic fragment in vegetative DNA not observed in any of the seed DNA samples. Ten of the observed polymorphisms were due to the appearance of a DNA fragment in response to a specific seed treatment while six were the result of the treatment-induced loss of a DNA fragment. The six polymorphisms resulting from the loss of a major fragment were all due to ambient-temperature seed storage. Results were reproducibly obtained from multiple DNA isolations using three separate DNA isolation procedures involving either multiple seed or a single seed as the template source. Therefore, genetically identical seed can consistently display RAPD polymorphisms as a response to the environmental exposure.
Modifications of a recent model by Izumi et al.1 on diffusion controlled growth of YBa2Cu3O7−x (123) superconductors are proposed, taking into account especially the engulfment process of the Y2BaCuO5 (211) particles into the solidifying 123 interface. The proposed modifications are evidenced by experimental results and applied to explain microstructural features of the 123 superconducting material. In particular, the 1:1 correlation between 123 platelet thickness (planar defect spacing) and 211 particle size as described by Jin et al.2 is explained by an observed bridge growth resulting in a zipper-like mechanism. By this mechanism the platelets grow together in an oriented way leading to a quasi single crystalline material.
Hemp dogbane is sensitive to fluroxypyr and tolerant to clopyralid. Absorption, translocation, and metabolism of clopyralid and fluroxypyr were studied in hemp dogbane to determine if differences in these processes could be responsible for differential sensitivity. In addition, the effect of growth stage on herbicide absorption and translocation was evaluated. The 14C-herbicides were applied to the adaxial side of a single leaf located near the midpoint of hydroponically cultured plants. Uptake of fluroxypyr was more rapid than clopyralid. At 72 h after treatment (HAT), fluroxypyr and clopyralid absorption was 62 and 38%, respectively. Clopyralid was much more mobile than fluroxypyr, with 75% of the absorbed 14C from 14C-clopyralid recovered outside the treated leaf compared to only 45% for fluroxypyr 72 HAT. Relative to fluroxypyr, a higher percentage of 14C-clopyralid recovered outside the treated leaf translocated acropetally, especially when plants were treated during the vegetative stage. Treatment during the early reproductive stage increased basipetal and reduced acropetal translocation relative to the vegetative stage. Neither herbicide was metabolized rapidly. Approximately 60 and 90% of the recovered 14C was attributable to unaltered fluroxypyr and clopyralid, respectively, 72 HAT. Some differences in absorption, translocation, and metabolism between clopyralid and fluroxypyr exist, but they cannot fully account for differential sensitivity of hemp dogbane to these two herbicides. Differences in activity at the target site may be responsible for differential activity of these herbicides on hemp dogbane.