Evidence for partial quenching of orbital angular momentum upon complex formation in the infrared spectrum of OH-acetylene

The entrance channel leading to the addition reaction between the hydroxyl radical and acetylene has been examined by spectroscopic characterization of the asymmetric CH stretching band of the π-hydrogen bonded OH-acetylene reactant complex. The infrared action spectrum observed at 3278.6 cm−1 (origin) consists of seven peaks of various intensities and widths, and is very different from those previously reported for closed-shell HF/HCl-acetylene complexes. The unusual spectrum arises from a partial quenching of the OH orbital angular momentum in the complex, which in turn is caused by a significant splitting of the OH monomer orbital degeneracy into 2A′ and 2A″ electronic states. The magnitude of the 2A′−2A″ splitting as well as the A rotational constant for the OH-acetylene complex are determined from the analysis of this b-type infrared band. The most populated OH product rotational state, jOH = 9/2, is consistent with intramolecular vibrational energy transfer to the ν2 C≡C stretching mode of the departing acetylene fragment. The lifting of the OH orbital degeneracy and partial quenching of its electronic orbital angular momentum indicate that the electronic changes accompanying the evolution of reactants into products have begun to occur in the reactant complex

Infrared spectrum and stability of a π-type hydrogen-bonded complex between the OH and C2H2 reactants

A hydrogen-bonded complex between the hydroxyl radical and acetylene has been stabilized in the reactant channel well leading to the addition reaction and characterized by infrared action spectroscopy in the OH overtone region. Analysis of the rotational band structure associated with the a-type transition observed at 6885.53(1) cm−1 (origin) reveals a T-shaped structure with a 3.327(5) Å separation between the centers of mass of the monomer constituents. The OH (v = 1) product states populated following vibrational predissociation show that dissociation proceeds by two mechanisms: intramolecular vibrational to rotational energy transfer and intermolecular vibrational energy transfer. The highest observed OH product state establishes an upper limit of 956 cm−1 for the stability of the π-type hydrogen-bonded complex. The experimental results are in good accord with the intermolecular distance and well depth at the T-shaped minimum energy configuration obtained from complementary ab initio calculations, which were carried out at the restricted coupled cluster singles, doubles, noniterative triples level of theory with extrapolation to the complete basis set limit

Transit Network Complexity in the Context of Transit Itinerary Inference with Travel Survey Data and GTFS

Researchers and planners have taken great interest in the rich data-resource that smartphone and GPS travel surveys can now produce. The interpretation of this data has become a popular topic with methods such as transit itinerary inference (TII) from travel survey data and GTFS emerging as useful tools in the field of travel behavior analysis. This exploratory research develops metrics to quantify a characteristic of GTFS data that complicates the overlay processing of travel survey GPS points and bus route geometries in TII: the spatiotemporal overlap of bus routes in the GTFS record. Accurate route inference is difficult in regions where rider data coincides with overlapping routes and various TII approaches have been tested to address this challenge. In this research, detecting overlap, and quantifying the degree of overlap on road links is achieved in 5 study regions through the application of two proposed measures: The Overlapping Routes on Links (OROL) index, and the Probability of Passage (POP) score. The latter’s output is seen as one way to improve route matching rates in TII. These measures build off the traditional Line Overlapping Index (LOI) and improve upon it by providing previously unobtainable road-link level detail; the OROL index, in fact, represents a spatially precise decomposition of the LOI. To ensure accurate analysis between networks, an additional novel procedure is developed that converts GTFS data into a simplified stand-in road network representation, thus providing a base layer for disaggregate network measures, and replacing the need for additional road network sources entirely

Usability Testing – An Aphasia Perspective

This paper reports the experience of participating in usability testing from the perspective of a person with aphasia. We briefly report adaptations to classic usability testing to enable the participation of people with aphasia. These included the use of short, direct tasks and physical artefacts such as picture cards. Authors of the paper include Ian, a user with aphasia who participated in adapted usability testing and Abi, a speech and language therapist researcher who facilitated sessions. Ian reports that these methods allowed him, as a person with aphasia, to engage with the usability testing process. We argue that such adaptations are essential in order to develop technologies which will be accessible to people with aphasia. This collaborative report provides a case for both how and why these adaptations can be made

Nutrient enrichment induces a shift in dissolved organic carbon (DOC) metabolism in oligotrophic freshwater sediments

Dissolved organic carbon (DOC) turnover in aquatic environments is modulated by the presence of other key macronutrients, including nitrogen (N) and phosphorus (P). The ratio of these nutrients directly affects the rates of microbial growth and nutrient processing in the natural environment. The aim of this study was to investigate how labile DOC metabolism responds to changes in nutrient stoichiometry using 14C tracers in conjunction with untargeted analysis of the primary metabolome in upland peat river sediments. N addition led to an increase in 14C-glucose uptake, indicating that the sediments were likely to be primarily N limited. The mineralisation of glucose to 14CO2 reduced following N addition, indicating that nutrient addition induced shifts in internal carbon (C) partitioning and microbial C use efficiency (CUE). This is directly supported by the metabolomic profile data which identified significant differences in 22 known metabolites (34% of the total) and 30 unknown metabolites (16% of the total) upon the addition of either N or P. 14C-glucose addition increased the production of organic acids known to be involved in mineral P dissolution (e.g. gluconic acid, malic acid). Conversely, when N was not added, the addition of glucose led to the production of the sugar alcohols, mannitol and sorbitol, which are well known microbial C storage compounds. P addition resulted in increased levels of several amino acids (e.g. alanine, glycine) which may reflect greater rates of microbial growth or the P requirement for coenzymes required for amino acid synthesis. We conclude that inorganic nutrient enrichment in addition to labile C inputs has the potential to substantially alter in-stream biogeochemical cycling in oligotrophic freshwaters

Quantifying the contribution of riparian soils to the provision of ecosystem services

Riparian areas, the interface between land and freshwater ecosystems, are considered to play a pivotal role in the supply of regulating, provisioning, cultural and supporting services. Most previous studies, however, have tended to focus on intensive agricultural systems and only on a single ecosystem function. Here, we present the first study which attempts to assess a wide range of ecological processes involved in the provision of the ecosystem service of water quality regulation across a diverse range of riparian typologies. Specifically, we focus on 1) evaluating the spatial variation in riparian soils properties with respect to distance with the river and soil depth in contrasting habitat types; 2) gaining further insights into the underlying mechanisms of pollutant removal (i.e. pesticide sorption/degradation, denitrification, etc.) by riparian soils; and 3) quantify and evaluate how riparian vegetation across different habitat types contribute to the provision of watercourse shading. All the habitats were present within a single large catchment and included: (i) improved grassland, (ii) unimproved (semi-natural) grassland, (iii) broadleaf woodland, (iv) coniferous woodland, and (iv) mountain, heath and bog. Taking all the data together, the riparian soils could be statistically separated by habitat type, providing evidence that they deliver ecosystem services to differing extents. Overall, however, our findings seem to contradict the general assumption that soils in riparian area are different from neighbouring (non-riparian) areas and that they possess extra functionality in terms of ecosystem service provision. Watercourse shading was highly habitat specific and was maximal in forests (ca. 52% shade cover) in comparison to the other habitat types (7–17%). Our data suggest that the functioning of riparian areas in less intensive agricultural areas, such as those studied here, may be broadly predicted from the surrounding land use, however, further research is required to critically test this across a wider range of ecosystems

Delineating and mapping riparian areas for ecosystem service assessment

Riparian buffers, the interface between terrestrial and freshwater ecosystems, have the potential to protect water bodies from land-based pollution, and also for enhancing the delivery of a range of ecosystem services. The UK currently has no defined optimal width or maximum extent of riparian buffers for specific ecosystem services. Here, we present the first study, which attempts to (a) compare and critique different riparian buffer delineation methods and (b) investigate how ecological processes, for example, pollutant removal, nutrient cycling, and water temperature regulation, are affected spatially by proximity to the river and also within a riparian buffer zone. Our results have led to the development of new concepts for riparian delineation based on ecosystem service-specific scenarios. Results from our study suggest that choice of delineation method will influence not only the total area of potential riparian buffers but also the proportion of land cover types included, which in turn will determine their main ecosystem provision. Thus, for some ecological processes (e.g., pollutant removal), a fixed-distance approach will preserve and protect its ecosystem function, whereas for processes such as denitrification, a variable-width buffer will reflect better riparian spatial variability maximizing its ecological value. In summary, riparian delineation within UK habitats should be specific to the particular ecosystem service(s) of interest (e.g., uptake of nutrients and shading), and the effectiveness of the buffer should be ground-truthed to ensure the greatest level of protection

The Role of Monitoring Interpretive Rates, Concordance Between Cytotechnologist and Pathologist Interpretations Before Sign-Out, and Turnaround Time in Gynecologic Cytology Quality Assurance Findings From the College of American Pathologists Gynecologic Cytopathology Quality Consensus Conference Working Group 1

Context.-The College of American Pathologists (CAP) conducted a national survey of gynecologic cytology quality assurance (QA) practices. Experts in gynecologic cytology were asked to join 5 working groups that studied the survey data on different aspects of QA. Evaluating the survey data and follow-up questions online, together with a review of pertinent literature, the working groups developed a series of preliminary statements on good laboratory practices in cytology QA. These were presented at a consensus conference and electronic voting occurred. Objective.-To evaluate a set of QA monitors in gynecologic cytology. Working group 1 evaluated (1) monitoring interpretive rate categories for Papanicolaou tests (Pap tests), (2) concordance of cytotechnologist and pathologist interpretations before sign-out, and (3) turnaround time for Pap tests. Data Sources.-The statements are based on a survey of gynecologic cytology QA practice patterns and of opinions from working group members and consensus conference attendees. Conclusions.-The outcomes of this process demonstrate the current state of practice patterns in gynecologic cytology QA. Monitoring interpretive rates for all Bethesda System categories is potentially useful, and it is most useful to monitor interpretive rates for cytotechnologists individually and in comparison to the entire laboratory. Laboratories need to determine what level of discrepancy between cytotechnologist and pathologist interpretations of Pap tests is important to track. Laboratories should consider formalizing procedures and policies to adjudicate such discrepant interpretations. Turnaround time should be monitored in gynecologic cytology, but individual laboratories should determine how to measure and use turnaround time internally

Variation in dissolved organic matter (DOM) stoichiometry in UK freshwaters:Assessing the influence of land cover and soil C:N ratio on DOM composition

Dissolved organic matter (DOM) plays an important role in freshwater biogeochemistry. To investigate the influence of catchment character on the quality and quantity of DOM in freshwaters, forty-five sampling sites draining subcatchments of contrasting soil type, hydrology and land cover within one large upland-dominated and one large lowland-dominated catchment, were sampled over a one-year period. Dominant land cover in each subcatchment included: arable and horticultural, blanket peatland, coniferous woodland, improved-, unimproved-, acid- and calcareous-grasslands. The composition of the C, N, and P pool was determined as a function of the inorganic nutrient species (NO3-, NO2-, NH4+, PO43-) and dissolved organic nutrient (DOC, DON and DOP) concentrations. DOM quality was assessed by calculation of the molar DOC:DON and DOC:DOP ratios and specific ultraviolet absorbance (SUVA254). In catchments with little anthropogenic nutrient inputs, DON and DOP typically comprised >80% of the TDN and TDP concentrations. By contrast, in heavily impacted agricultural catchments DON and DOP typically comprised 5-15% of TDN and 10-25% of TDP concentrations. Significant differences in DOC:DON and DOC:DOP ratios were observed between land cover class with significant correlations observed between both the DOC:DON and DOC:DOP molar ratios and SUVA254 (rs = 0.88 and 0.84, respectively). Analysis also demonstrated a significant correlation between soil C:N ratio and instream DOC:DON/DOP (rs = 0.79 and 0.71 respectively). We infer from this that soil properties, specifically the C:N ratio of the soil organic matter pool, has a significant influence on the composition of DOM in streams draining through these landscapes