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Obtaining accurate age determinations from minerals in archaeological ash is a major unsolved issue in radiocarbon (14C) dating. This is because the original 14C content of calcite, the main component of ash, is altered by isotopic exchange. Pyrogenic aragonite, another mineral phase recently discovered in ash, might preserve its 14C signature through time. Using a new method based on density separation and step combustion, we were able to isolate and date aragonitic ash from an archaeological destruction horizon of known age. Here we show that the 14C age of aragonite matches the age of the destruction horizon. Our results demonstrate that pyrogenic aragonite is a short-lived material suitable for 14C dating and directly related to human activities involving the use of fire, thus bearing major implications for the establishment of absolute chronologies for the past 50,000 yr.
Radiation-tolerant materials, sensors and electronics can enable lightweight space subsystems with reduced packaging requirements and increased operation lifetimes. Such technology can be used within extreme harsh environments related to space exploration, radiation medicine and power generation (combustion and nuclear). Gallium nitride (GaN), a ceramic semiconductor material, is a candidate material due to its stability within high-radiation, high-temperature and chemically corrosive environments. In addition, the wide bandgap of GaN (3.4 eV) can be leveraged for ultraviolet (UV) wavelength photodetection. In metal-semiconductor-metal (MSM) photodetector architectures using Schottky contacts, transparent electrodes (e.g., graphene) can increase sensitivity and improve overall device response. Here we present fabrication and characterization of GaN-based UV photodetectors using graphene electrodes irradiated up to 200 krad total ionizing dose (TID) then tested under UV light and dark conditions. For current-voltage measurements taken at 90, 120 and 200 krad TID, the current-voltage response does not vary significantly. From 90 to 120 krad TID, the responsivity shifts by 2% before dropping off at 200 krad TID. These initial findings suggest that graphene/GaN MSM UV photodetectors can provide robust operation within extreme harsh environments.
On 2 November 2010, the voters of Oklahoma passed the so-called “Save Our State Amendment.” This amendment to Oklahoma's constitution prohibited Oklahoma courts from “look[ing] to the legal precepts of other nations or cultures. Specifically,” it asserted, “the courts shall not consider international law or Sharia Law.” This legislative moment in middle America passed quickly. Commentators both inside and outside the United States responded to the amendment with bewilderment—and in 2012, a federal appeals court ruled the amendment unconstitutional. “Save Our State” died before it could have any far-reaching effect.
As device sizes are scaled down nearly to their atomic limits, the development of economically viable methods which may continue to improve device performance in accordance with Moore’s Law becomes ever more challenging. The recently developed technique of Electroplate-and-Lift (E&L) lithography promises to be an inexpensive, widely applicable method for the reproducible, controlled fabrication of micro- and nanostructures. In this study, E&L is applied to the fabrication of patterned copper micro- and nanowires as a model system. Copper wires with diameters ranging from 10 m to 200 nm have been produced using a single ultrananocrystalline diamond (UNCD)TM template, by varying only the electroplating time.
To quantify the relationship between copper wire diameter and deposition time, wires were electroplated at -0.4 V vs. the saturated calomel electrode (SCE) for durations between 2.5 and 160 s, then imaged by optical microscopy and/or scanning electron microscopy (SEM). Images were analyzed by identifying wire segments with ImageJ and examining the statistical distribution of wire diameters using Excel. This analysis verified theoretical predictions of a linear dependence between mean wire diameter and the square root of growth time.
Background: This paper looks at attrition in relation to deprivation and type of therapy – CBT or person-centred counselling. Method: Case notes of all those referred in a 4-month period (n = 497) were assessed for those who failed to opt-in; those who opted-in but failed to attend first appointment and those who attended first appointment but subsequently dropped-out. Results: Significant numbers failed to opt-in, attend first appointment or dropped out during therapy. There were no differences between CBT and PCT. Those from the most deprived areas were less likely to opt-in. Conclusions: We need to develop better approaches to attracting and maintaining contact with individuals complaining of common mental health problems.
A deep ice core has been drilled on Akademii Nauk ice cap, Severnaya Zemlya, Eurasian Arctic. High-resolution chemical analysis has been carried out for the upper 53 m of this ice core to study its potential as an atmospheric aerosol archive, despite strong meltwater percolation. These records show that a seasonal atmospheric signal cannot be deduced. However, strong year-to-year variations have allowed the core to be dated, and a mean annual net mass balance of 0.46 m w.e. a-1 was deduced. The chemical signature of an extraordinarily high peak in electrical conductivity at 26 m depth pointed clearly to the eruption of Bezymianny, Kamchatka, in 1956. However, in general, peaks in the electrical conductivity are not necessarily related to deposition of volcanogenic sulphur aerosol. In contrast, maximum sulphate and nitrate concentrations in the ice could be related to maximum SO2 and NOx anthropogenic emissions in the 1970s, probably caused by the nickel- and copper-producing industries in Norilsk and on the Kola peninsula or by industrial combustion processes occurring in the Siberian Arctic. In addition, during recent decades sulphate and nitrate concentrations declined by 80% and 60%, respectively, reflecting a decrease in anthropogenic pollution of the Arctic basin.
We describe how the composition of an organic - based magnet can be controlled by varying the Chemical Vapor Deposition (CVD) conditions. A study was conducted for the Co2(CO)8/ TCNE system to form cobalt tetracyanoethylene [Co(TCNE)x, x∼2, a paramagnetic material], and for the V(CO)6/ TCNEx system to form vanadium tetracyanoethylene [V(TCNE)x, x∼2, a ferrimagnetic material]. Thin V(TCNE)x, x∼2 films (∼0.05-0.5 μm) with room temperature conductivity of 10-4<σRT<10-3S/cm and magnetic ordering temperature Tc of up to ∼400K were deposited. The V(TCNE)x, x∼2 thin films have the potential for incorporation in a spin-valve device as one of the magnetic contacts, and are promising candidates to form optically controlled magnetic-based structures.
We introduce an objective method for classifying phonological overlap between Spanish and English translation equivalents. This method then is exploited to examine spoken word recognition using stimuli with graded levels of phonological overlap. Performance by typical English-only speaking (EO) children and English-only children with primary language impairment (LI) is compared to a control group of bilingual Spanish–English peers (BI). Response time and accuracy separated groups, with the BI group outperforming the EO group, who in turn outperformed the LI group. Children with more severe LI are slower than those with mild LI, and LI severity is significantly correlated with speed. The two groups of monolingual children and the LI subgroups respond in a qualitatively similar way to decreasing phonological overlap.
The aim of the present study was to compare the response of a range of atherogenic and thrombogenic risk markers to two dietary levels of saturated fatty acid (SFA) substitution with monounsaturated fatty acids (MUFA) in students living in a university hall of residence. Although the benefits of such diets have been reported for plasma lipoproteins in high-risk groups, more needs to be known about effects of more modest SFA-MUFA substitutions over the long term and in young healthy adults. In a parallel design over 16 weeks, fifty-one healthy young subjects were randomised to one of two diets: (1) a moderate-MUFA diet in which 16 g dietary SFA/100 g total fatty acids were substituted with MUFA (n 25); (2) a high-MUFA diet in which 33 g dietary SFA/100 g total fatty acids were substituted with MUFA (n 26). All subjects followed an 8-week run-in diet (reference diet), with a fatty acid composition close to the UK average values. There were no differences in plasma lipid responses between the two diets over 16 weeks of the study with similar reductions in total cholesterol (P <0·001) and LDL-cholesterol (P<0·01) in both groups; a small but significant reduction in HDL-cholesterol was also observed in both groups (P<0·01). Platelet responses to ADP (P<0·01) and arachidonic acid (P<0·05) differed with time on the two diets; at 16 weeks, platelet aggregatory response to ADP was significantly lower on the high-MUFA than the moderate-MUFA (P<0·01) diet; ADP responses were also significantly lower within this group at 8 (P<0·05) and 16 (P<0·01) weeks compared with baseline. There were no differences in fasting factor VII activity (factors VIIc and VIIag), fibrinogen concentration or tissue-type plasminogen activator activity between the diets. There were no differences in postprandial factor VIIc responses to a standard meal (area under the curve) between the diets after 16 weeks, but postprandial factor VIIc response was lower than on the high-MUFA diet compared with baseline (P<0·01). In conclusion, a high-MUFA diet sustains potentially beneficial effects on platelet aggregation and postprandial activation of factor VII. Moderate or high substitution of MUFA for SFA achieves similar reductions in fasting blood lipids in young healthy subjects.
A novel flow-through microparticle detector was deployed concurrently with continuous flow analyses of major ions during the North Greenland Icecore Project 2000 field season. the easy-handling detector performs continuous counting and sizing. In this deployment the lower size-detection limit was conservatively set to 1.0 μm equivalent spherical particle diameter, and a depth resolution of ≤1cm was achieved for microparticle concentrations. the dust concentration usually followed the Ca2+ variability. Here results are presented from an inspection of the Ca/dust mass ratio in 23 selected intervals, 1.65 m long each, covering different climatic periods including Holocene and Last Glacial Maximum (LGM). A (Ca2+)/(insoluble dust) mass ratio of 0.29 was found for the Holocene and 0.11 for LGM. Changes to the Ca/dust ratio occur on an annual to multi-annual time-scale exhibiting the same pattern, i.e. a lower Ca/dust ratio for higher crustal concentrations. Moreover, the Ca2+/dust ratio may increase significantly during episodic events such as volcanic horizons due to enhanced dissolution of CaCO3. This calls into question the notion of deploying Ca2+ as a quantitative mineral dust reference species and shows the importance of variable source properties or fractionating processes during transport and deposition.