Direct measurement of carbon-14 in carbon dioxide by liquid scintillation counting

Liquid scintillation counting technique is applied to the direct measurement of carbon-14 in carbon dioxide. This method has high counting efficiency and eliminates many of the basic problems encountered with previous techniques. The technique can be used to achieve a percent substitution reaction and is of interest as an analytical technique

Recent development in organic scintillators

Discussion on recent developments of organic scintillators includes studies of organic compounds that form glass-like masses which scintillate and are stable at room temperature, correlations between molecular structure of organic scintillators and self-quenching, recently developed fast scintillators, and applications of liquid-scintillation counters

Low Rank Vector Bundles on the Grassmannian G(1,4)

Here we define the concept of $L$-regularity for coherent sheaves on the Grassmannian G(1,4) as a generalization of Castelnuovo-Mumford regularity on ${\bf{P}^n}$. In this setting we prove analogs of some classical properties. We use our notion of $L$-regularity in order to prove a splitting criterion for rank 2 vector bundles with only a finite number of vanishing conditions. In the second part we give the classification of rank 2 and rank 3 vector bundles without "inner" cohomology (i.e. H^i_*(E)=H^i(E\otimes\Q)=0 for any $i=2,3,4$) on G(1,4) by studying the associated monads.Comment: 11 pages, no figure

Ages on weathered Plio-Pleistocene tephra sequences, western North Island, New Zealand

Using the zircon fission-track method, we have obtained five ages on members of two strongly-weathered silicic, Pliocene-Pleistocene tephra sequences, the Kauroa and Hamilton Ash formations, in western North Island, New Zealand. These are the first numerical ages to be obtained directly on these deposits. Of the Kauroa Ash sequence, member K1 (basal unit) was dated at 2.24 ± 0.29 Ma, confirming a previous age of c. 2.25 Ma obtained (via tephrochronology)from K/Ar ages on associated basalt lava. Members K2 and K3 gave indistinguishable ages between 1.68 ± 0.12 and 1.43 ± 0.17 Ma. Member K12, a correlative of Oparau Tephra and probably also Ongatiti Ignimbrite, was dated at 1.28 ± 0.11 Ma, consistent with an age of 1.23 ± 0.02 Ma obtained by various methods on Ongatiti Ignimbrite. Palaeomagnetic measurements indicated that members K13 to K15 (top unit, Waiterimu Ash) are aged between c. 1.2 Ma and 0.78 Ma. Possible sources of the Kauroa Ash Formation include younger volcanic centres in the southern Coromandel Volcanic Zone or older volcanic centres in the Taupo Volcanic Zone, or both. Of the Hamilton Ash sequence, the basal member Ohinewai Ash (HI) was dated at 0.38 ± 0.04 Ma. This age matches those obtained by various methods on Rangitawa Tephra of 0.34-0.35 Ma, supporting correlation with this Whakamaru-caldera derived deposit. The origin of the other Hamilton Ash beds is unknown but various younger volcanic centres in the Taupo Volcanic Zone are possible sources. The topmost member, Tikotiko Ash (H6-H7), is estimated to be aged between c. 0.18 and 0.08 Ma. Various silicic pyroclastic deposits documented in North Island and in marine cores may be co-eval with members of the Kauroa Ash and Hamilton Ash sequences on the basis of their age

Diffusion Models of Mass Transport for the Characterisation of Amperometric Gas Sensors

\ua9 2024 The Authors. ChemElectroChem published by Wiley-VCH GmbH. A diffusion model for the analysis of chronoamperometric data in response to a concentration step is developed for amperometric gas sensors. This analysis avoids the difficulties with standard potentiodynamic measurements at the large specific area, high capacitance electrodes employed in these sensors. Despite the fact that typical devices comprise multiple layers with varying thicknesses and diffusivities, we show that typical chronoamperometric traces can be fitted to a simple diffusion model with a single parameter (Formula presented.) where L is an overall effective thickness of the diffusion barrier and D is an effective diffusion coefficient. Through a comparison of the transient and steady-state current, independent estimates of L and D in the devices can be made. The model is also extended to cover cases with interfacial kinetic barriers; such kinetic limitations lead to a change in the effective values L and D, but the simple diffusion model remains a good fit to the data. This analysis shows that transient sensor responses can be characterised by a single parameter τ and conversely that deviations from this regression model cannot be assigned to (i) complex layer architectures or (ii) interlayer kinetic barriers. Instead, we show that non-uniform accessibility effects arising from a distribution of diffusion rates across the device lead to deviations from the simple regression model, but that they may be captured approximately by a more complex model in which τ has a probability distribution

Developing an inquiry-based learning module with consideration of quality by design principles for biomedical science students

To help students develop into confident and effective laboratory scientists it is necessary to facilitate their understanding and ability to participate effectively in all processes involved in experimental design and implementation in an engaging and realistic manner. Our challenge was to develop a 20-credit, ordinary degree (without honours) level, practical skills-based module for Biomedical Science students who are not on a National Health Service placement that encompasses elements of professionalism. We describe the design of a module that utilises Inquiry-based learning (IBL) and Quality by Design (QbD) principles and discuss staff experience and reflections following analysis of six years of anonymised module feedback data which includes quantitative and qualitative data. Key positive themes from the qualitative analysis were satisfaction at being able to make evidenced based decisions for changes in experimental factors and development of personal skills which was perceived as helpful for their preparation for their honours year project. The level of challenge that the format of the module presented was perceived negatively. We conclude that this mode of learning is challenging to implement and monitor for academics and challenges students intellectual and professional development, but that the benefits are worth the investment

Stratigraphy, chronology, and correlation of the Plio-Pleistocene (c. 2.2-0.8 Ma) Kauroa Ash sequence, western central North Island, New Zealand

The Kauroa Ash beds (K-beds) comprise a 12-20 m-thick sequence of extremely weathered, clay-rich (40-95% <4 μm clay) beds of tephra and loess, and associated paleosols. Found in isolated remnants throughout the western central North Island, the sequence comprises 15 defined members, with as many as 44 constituent macroscopic beds. The type site, ‘Woodstock’, near Raglan, is the most comprehensive sequence known, but other sites (e.g. Papakura Creek and Tiritirimatangi Peninsula) contain units not found or poorly defined at Woodstock. Field properties as well as magnetic susceptibility measurements and particle-size analysis characterise the facies in the sequence. Field properties (in particular colour, consistence, macrofabric) describe the lithostratigraphy. The sequence contains five interpretive (i.e. genetic) ‘facies’: paleosols, primary tephra, very weathered tephra (possibly composite beds), loess and ‘tephric loess’ beds. At least seven loess beds are (newly) identified in the sequence: K4a, K5, K6ai, K8ai, K8bi, K10a and K14ai. Mass-specific susceptibility and frequency-dependent susceptibility results partly conform to established models (developed mostly on Chinese loess-paleosol deposits) of susceptibility enhancement in paleosols and depletion in loess. Many parts of the sequence do not appear to conform to this model and the results more closely resemble the inverse relationship found on Alaskan loess-paleosol beds. Frequency-dependent susceptibility is reliable in delineating paleosols by their ‘ultrafine’ ferrimagnetic mineral content, and citrate-bicarbonate-dithionite treatments successfully remove all iron oxides so that remeasurement of susceptibility isolates a strictly ‘pedogenic’, rather than lithogenic, fraction. Laser diffraction particle-size analysis shows that the Kauroa Ash beds are texturally reasonably homogenous. They have bimodal particle-size distributions with the most dominant mode at around 11.25 ɸ inferred to be the product of intense and prolonged weathering. Other modes are variously centred on 7-8.5 ɸ and, despite weathering and pedogenesis, have some relationship to the original depositional particle-size distributions because trends between facies (i.e. genetic units) are delineated. Principal components analysis objectively characterises these modes as (Wentworth size classes) ‘very fine clay’ and ‘coarse silt’, although there is no proportional relationship between them, supporting a post-depositional origin for the former mode. The chronology of the sequence, previously poorly defined, is greatly improved by a combination of tephrochronologic correlations, fission-track dating, and paleomagnetism. Five zircon fission-track dates provide independent age ‘spikes’ and range from 2.24 ± 0.29 Ma in the basal member, K1, to 1.28 ± 0.11 Ma for the distal ignimbrite unit K12a. Paleomagnetism is invaluable in providing additional age information. The top of the sequence, member K15, is dated as >0.78 Ma (Brunhes-Matuyama boundary) because of its reversed polarity; two episodes of normal polarity are found in beds K14b and K2b and are inferred to represent the Jaramillo (1.07-0.99 Ma) and Olduvai (1.95-1.79 Ma) subchrons, respectively. Beds underlying the Kauroa Ash sequence are also of normal polarity, indicating that they were deposited in the Gauss Chron (>2.6 Ma). Identification and correlation of tephras by conventional means (fingerprinting by their lithological or geochemical properties) is impossible in the Kauroa Ash sequence because the beds have no remaining volcanic glass, which has instead been altered to an assemblage of authigenic phases (clays) by weathering and pedogenesis. However, a new technique analysing fresh glass found as melt inclusions in quartz grains is successful in circumventing this problem. Inclusions represent samples of non-degassed magma that became entrapped during phenocryst growth prior to eruption. The glass has remained unaltered because it is hermetically sealed in a chemically resistant phenocryst, which has protected it from weathering processes. Electron microprobe analysis of the glass inclusions yield results which are wholly reasonable for glass (totals ranging from 93-97%; low standard deviations of <1 %), and a number of provisional correlations are established by comparing the major element composition of Kauroa Ash tephra beds with those of proximal deposits. The Kauroa Ash sequence may contain deposits correlated with at least seven major TVZ eruptions, in many cases expanding the known extent of the (distal) deposit and, for the first time answering the question as to the origin of the Kauroa Ash beds. These correlations, together with an improved chronology, enable the Kauroa Ash sequence to be placed in a regional stratigraphic framework alongside other New Zealand Plio-Pleistocene sequences such as those in the Wanganui Basin, Wairarapa, Cape Kidnappers and Port Waikato. Using paleosols as chrono- and climatostratigraphic entities (correlated to warm periods in global climate), the sequence can also be placed alongside a global reference, the marine oxygen isotope stratigraphy. A further correlation to the Chinese loess-paleosol record suggests that large parts of the Kauroa Ash sequence were deposited in an incremental manner akin to deposition of loess, so that the sequence is not only a record of TVZ volcanism, but also of Plio-Pleistocene paleoclimate

Attitudes towards clinical services among people who self-harm: systematic review.

BACKGROUND: Self-harm is increasingly common in many countries, is often repeated and may have other negative outcomes. AIMS: To systematically review people's attitudes towards clinical services following self-harm in order to inform service design and improvement. METHOD: A search of electronic databases was conducted and experts in the field were contacted in order to identify relevant worldwide qualitative or quantitative studies. Data were extracted independently by two reviewers with more weight given to studies of greater quality and relevance. RESULTS: Thirty-one studies met the inclusion criteria. Despite variations in healthcare systems and setting, participants' experiences were remarkably similar. Poor communication between patients and staff and a perceived lack of staff knowledge with regard to self-harm were common themes. Many participants suggested that psychosocial assessments and access to after-care needed to be improved. CONCLUSIONS: Specific aspects of care that might increase service user satisfaction and treatment adherence include staff knowledge, communication and better after-care arrangements. A standard protocol could aid regular audits of users' experiences of services