Recent Submissions

  • Can contrast-response functions indicate visual processing levels?

    Breitmeyer, B.G.; Tripathy, Srimant P.; Brown, J.M. (2018-03-01)
    Many visual effects are believed to be processed at several functional and anatomical levels of cortical processing. Determining if and how the levels contribute differentially to these effects is a leading problem in visual perception and visual neuroscience. We review and analyze a combination of extant psychophysical findings in the context of neurophysiological and brain-imaging results. Specifically using findings relating to visual illusions, crowding, and masking as exemplary cases, we develop a theoretical rationale for showing how relative levels of cortical processing contributing to these effects can already be deduced from the psychophysically determined functions relating respectively the illusory, crowding and masking strengths to the contrast of the illusion inducers, of the flankers producing the crowding, and of the mask. The wider implications of this rationale show how it can help to settle or clarify theoretical and interpretive inconsistencies and how it can further psychophysical, brain-recording and brain-imaging research geared to explore the relative functional and cortical levels at which conscious and unconscious processing of visual information occur. Our approach also allows us to make some specific predictions for future studies, whose results will provide empirical tests of its validity.
  • Bottlenecks of motion processing during a visual glance: the leaky flask model

    Ogmen, H.; Ekiz, O.; Huynh, D.; Bedell, H.E.; Tripathy, Srimant P. (2013-12-31)
    Where do the bottlenecks for information and attention lie when our visual system processes incoming stimuli? The human visual system encodes the incoming stimulus and transfers its contents into three major memory systems with increasing time scales, viz., sensory (or iconic) memory, visual short-term memory (VSTM), and long-term memory (LTM). It is commonly believed that the major bottleneck of information processing resides in VSTM. In contrast to this view, we show major bottlenecks for motion processing prior to VSTM. In the first experiment, we examined bottlenecks at the stimulus encoding stage through a partial-report technique by delivering the cue immediately at the end of the stimulus presentation. In the second experiment, we varied the cue delay to investigate sensory memory and VSTM. Performance decayed exponentially as a function of cue delay and we used the time-constant of the exponential-decay to demarcate sensory memory from VSTM. We then decomposed performance in terms of quality and quantity measures to analyze bottlenecks along these dimensions. In terms of the quality of information, two thirds to three quarters of the motion-processing bottleneck occurs in stimulus encoding rather than memory stages. In terms of the quantity of information, the motion-processing bottleneck is distributed, with the stimulus-encoding stage accounting for one third of the bottleneck. The bottleneck for the stimulus-encoding stage is dominated by the selection compared to the filtering function of attention. We also found that the filtering function of attention is operating mainly at the sensory memory stage in a specific manner, i.e., influencing only quantity and sparing quality. These results provide a novel and more complete understanding of information processing and storage bottlenecks for motion processing.
  • β‐Ketoiminato Iridium(III) Organometallic Complexes: Selective Cytotoxicity towards Colorectal Cancer Cells HCT116 p53‐/‐

    Lord, Rianne M.; Zegke, Markus; Henderson, I.R.; Pask, C.M.; Shepherd, H.J.; McGowan, P.C. (2019-01-07)
    This report presents a new library of organometallic iridium(III) compounds of the type [Cp*IrCl(L)] (Cp*=pentamethylcyclopentadienyl and L=a functionalized β‐ketoiminato ligand) showing moderate to high cytotoxicity against a range of cancer cell lines. All compounds show increased activity towards colorectal cancer, with preferential activity observed against the immortalized p53‐null colorectal cell line, HCT116 p53‐/‐, with sensitivity factors (SF) up to 26.7. Additionally, the compounds have excellent selectivity for cancerous cells when tested against normal cell types, with selectivity ratios (SR) up to 35.6, contrary to that of cisplatin, which is neither selective nor specific for cancerous cells (SF=0.43 and SR=0.7–2.3). This work provides a preliminary understanding of the cytotoxicity of iridium compounds in the absence of p53 and has potential applications in treatment of cancers for which the p53 gene is absent or mutant.
  • Highly-ordered onion micelles made from amphiphilic highly-branched copolymers

    Canning, S.L.; Ferner, J.M.F.; Mangham, N.M.; Wear, T.J.; Reynolds, S.W.; Morgan, J.; Fairclough, J.P.A.; King, S.M.; Swift, Thomas; Geoghegan, M.; Rimmer, Stephen (2018)
    Uniform onion micelles formed from up to ten nano-structured polymer layers were produced by the aqueous self-assembly of highly-branched copolymers. Highly-branched poly(alkyl methacrylate)s were chain extended with poly(acrylic acid) in a two-step reversible addition–fragmentation chain transfer-self-condensing vinyl polymerization (RAFT-SCVP) in solution. The resulting polymers were dispersed into water from oxolane (THF) using a self-organized precipitation-like method and the self-assembled particles were studied by phase-analysis light scattering, small-angle neutron scattering, and electron microscopy techniques. The relative hydrophobicity of the blocks was varied by changing the alkyl methacrylate (methyl, butyl, or lauryl) and this was found to affect the morphology of the particles. Only the poly(butyl methacrylate)-containing macromolecule formed an onion micelle structure. The formation of this morphology was observed to depend on: the evaporation of the good solvent (THF) during the self assembly process causing kinetic trapping of structures; the pH of the aqueous phase; and also on the ratio of hydrophobic to hydrophilic segments within the copolymer. The lamellar structure could be removed by annealing the dispersion above the glass transition temperature of the poly(butyl methacrylate). To exemplify how these onion micelles can be used to encapsulate and release an active compound, a dye, rhodamine B (Rh B), was encapsulated and released. The release behaviour was dependent on the morphology of the particles. Particles formed containing the poly(methyl methacrylate) or poly (lauryl methacrylate) core did not form onions and although these materials absorbed Rh B, it was continuously released at room temperature. On the other hand, the lamellar structure formed from branchpoly( butyl methacrylate)-[poly(butyl methacrylate)-block-poly(acrylic acid)] allowed for encapsulation of approximately 45% of the dye, without release, until heating disrupted the lamellar structure.
  • Gaps, traps, bridges and props: a mixed-methods study of resilience in the medicines management system for heart failure patients at hospital discharge

    Fylan, Beth; Marques, Iuri; Ismail, Hanif; Breen, Liz; Gardner, P.; Armitage, Gerry R.; Blenkinsopp, Alison (2019)
    Poor medicines management places patients at risk, particularly during care transitions. For patients with heart failure (HF), optimal medicines management is crucial to control symptoms and prevent hospital readmission. This study explored the concept of resilience using HF as an example condition to understand how the system compensates for known and unknown weaknesses. We explored resilience using a mixed-methods approach in four healthcare economies in the north of England. Data from hospital site observations, healthcare staff and patient interviews, and documentary analysis were collected between June 2016 and March 2017. Data were synthesised and analysed using framework analysis. Interviews were conducted with 45 healthcare professionals, with 20 patients at three timepoints and 189 hours of observation were undertaken. We identified four primary inter-related themes concerning organisational resilience. These were named as gaps, traps, bridges and props. Gaps were discontinuities in processes that had the potential to result in poorly optimised medicines. Traps were features of the system that could produce errors or unintended adverse medication events. ‘Bridges’ were features of the medicines management system that promoted safety and continuity which ensured that, despite varying conditions, care could be delivered successfully. ‘Props’ were informal, temporary or impromptu actions taken by patients or healthcare staff to avoid potential adverse events. The numerous opportunities for HF patient safety to be compromised and sub-optimal medicines management during this common care transition are mitigated by system resilience. Cross-organisational bridges and temporary fixes or ‘props’ put in place by patients and carers, healthcare teams and organisations are critical for safe and optimal care to be delivered in the face of continued system pressures.
  • Inter-Ethnic and Demic-Group Variations in Craniofacial Anthropometry: A Review

    Jilani, Shelina K.; Ugail, Hassan; Logan, Andrew J. (2019)
    Craniofacial anthropometry plays an important role in facial structure. This review paper evaluates existing research surrounding population norms of studied facial parameters. The purpose is two-fold: (1) to determine variations in facial measurements due to demi-group or ethnic variations based on traditional (direct) caliper based and image based (indirect) anthropometric methods. (2) to compare where possible, measured facial parameters between referenced studies. Inter and intra-population variations in addition to sexual dimorphism of facial parameters such as the nose and eyes, singularly or in combination with one another, have been concluded. Ocular measurements have exhibited ethnic variations between males and females of the Saudi, Turkish, Egyptian and Iranian group. Moreover, demic variations are reported when the native language has been used a key criterion. It has been concluded that with the current state of migration and inter-demic marriages, the study of homogenous populations will prove difficult. Subsequently, this will result in ambiguous physical traits that are not representative for any one demic or ethnic population. In this paper, results for the following adult male and female populations have been discussed: African American, Azerbaijani, Caribbean, Chinese, Croatian, Egyptian, Italian, Iranian, Turkish, Saudi Arabian, Syrian and South African. The qualitative research presented serves as a knowledge base for learners and strikes up thought provoking concepts about the direction anthropometrical research is heading.
  • Being working class in the academy

    Craddock, P.W.; Archer, V.; Binns, Carole L.; Coogan, R.; Johnston, C. (2018-10)
    While widening access is high on universities' agendas at undergraduate level, class barriers still prevail in the academy. Here, ... working-class scholars describe their experiences of 'otherness'
  • A meta-framework for designing open data studies in psychology: ethical and practical issues of open qualitative data sets

    Branney, Peter; Reid, K.; Frost, N.; Coan, S.; Mathieson, A.; Woolhouse, M. (2019)
    To date, open science, and particularly open data, in Psychology, has focused on quantitative research. This paper aims to explore ethical and practical issues encountered by UK-based psychologists utilising open qualitative datasets. Semi-structured telephone interviews with eight qualitative psychologists were explored using a framework analysis. From the findings, we offer a context-consent meta-framework as a resource to help in the design of studies sharing their data and/or studies using open data. We recommend ‘secondary’ studies conduct archaeologies of context and consent to examine if the data available is suitable for their research questions. This research is the first we know of in the study of ‘doing’ (or not doing) open science, which could be repeated to develop a longitudinal picture or complemented with additional approaches, such as observational studies of how context and consent are negotiated in pre-registered studies and open data.
  • Zeitschrift fur Physikalische Chemie: Editorial

    Hickey, Stephen G.; Bund, A. (2011-02-25)
  • Type-I and Type-II Core-Shell Quantum Dots: Synthesis and Characterization

    Dorfs, D.; Hickey, Stephen G.; Eychmüller, A. (2010-02)
  • Evaluation of Alangium lamarckii bark for antiplasmodial and cytotoxic constituents and isolation of a novel tubulosine analogue

    Kantamreddi, Venkata Siva Satya Narayana; Marston, G.; Shnyder, Steven D.; Wright, Colin W. (2018-10)
    Alangium lamarkii is traditionally used in India for the treatment of malaria. Partial activity guided-fractionation of the basic chloroform fraction of the methanolic extract of the bark led to the isolation of a novel tubulosine analogue, 10-demethyl-9ˊ-N-methyltubulosine (1), for which the trivial name tubulosatine is suggested. In addition, the known A. lamarkii constituents, tubulosine (2), cephaeline and emetine were isolated as potent antiplasmodial and cytotoxic constituents, but 1 was up to 1000-fold less potent than the former alkaloids against both malaria parasites and human cancer cell lines. The compounds were active against both chloroquine-sensitive and chloroquine-resistant malaria parasites, but no selective toxicity was observed towards malaria parasites compared with cancer cells with any of the alkaloids. Further work to explore the basis for the relatively weak biological activities of 1 would be worthwhile. Betulinic acid, stigmasterol and its 3-O-glucoside were isolated from the neutral chloroform fraction of the methanolic extract.
  • Sensory memory is allocated exclusively to the current event-segment

    Tripathy, Srimant P.; Ögmen, H. (2018-09-07)
    The Atkinson-Shiffrin modal model forms the foundation of our understanding of human memory. It consists of three stores (Sensory Memory (SM), also called iconic memory, Short-Term Memory (STM), and Long-Term Memory (LTM)), each tuned to a different time-scale. Since its inception, the STM and LTM components of the modal model have undergone significant modifications, while SM has remained largely unchanged, representing a large capacity system funneling information into STM. In the laboratory, visual memory is usually tested by presenting a brief static stimulus and, after a delay, asking observers to report some aspect of the stimulus. However, under ecological viewing conditions, our visual system receives a continuous stream of inputs, which is segmented into distinct spatio-temporal segments, called events. Events are further segmented into event-segments. Here we show that SM is not an unspecific general funnel to STM but is allocated exclusively to the current event-segment. We used a Multiple-Object Tracking (MOT) paradigm in which observers were presented with disks moving in different directions, along bi-linear trajectories, i.e., linear trajectories, with a single deviation in direction at the mid-point of each trajectory. The synchronized deviation of all of the trajectories produced an event stimulus consisting of two event-segments. Observers reported the pre-deviation or the post-deviation directions of the trajectories. By analyzing observers' responses in partial- and full-report conditions, we investigated the involvement of SM for the two event-segments. The hallmarks of SM hold only for the current event segment. As the large capacity SM stores only items involved in the current event-segment, the need for event-tagging in SM is eliminated, speeding up processing in active vision. By characterizing how memory systems are interfaced with ecological events, this new model extends the Atkinson-Shiffrin model by specifying how events are stored in the first stage of multi-store memory systems.
  • Relating optical coherence tomography to visual fields in glaucoma: structure–function mapping, limitations and future applications

    Denniss, Jonathan; Turpin, A.; McKendrick, A.M. (2018)
    Combining information from optical coherence tomography (OCT) imaging and visual field testing is useful in the clinical assessment and monitoring of patients with glaucoma. Measurements of retinal nerve fibre layer thickness or neuroretinal rim width taken around the optic nerve head may be related to the visual field using a structure–function map. In this review, the structure–function mapping methods in clinical use are discussed. Typical clinical maps provide a population average, ‘one size fits all’ representation, but in recent years methods for customising structure–function maps to individual eyes have been developed and these are reviewed here. In the macula, visual field stimuli stimulate photoreceptors for which associated retinal ganglion cells are peripherally displaced. Recently developed methods that relate OCT measurements to visual field test locations in the macula are therefore also reviewed. The use of structure–function maps to relate OCT measurements to localised visual field sensitivity in new applications is also explored. These new applications include the selection of visual field test locations and stimulus intensities based on OCT data, and the formal post‐test combination of results across modalities. Such applications promise to exploit the structure–function relationship in glaucoma to improve disease diagnosis and monitoring of progression. Limitations in the validation and use of current structure–function mapping techniques are discussed.
  • Archaeology and modern reflections on death

    Dayes, Jennifer E.; Faull, C.; Büster, Lindsey S.; Green, Laura I.; Croucher, Karina T. (2018-09-22)
  • From Plastered Skulls to Palliative Care: What the Past Can Teach Us About Dealing with Death

    Büster, Lindsey S.; Croucher, Karina T.; Dayes, Jennifer E.; Green, Laura I.; Faull, C. (2018)
    Modern, advanced healthcare detects and monitors long-term and life-limiting illness more comprehensively than ever before. However, death is now often considered medical failure, and is a virtually taboo topic of conversation in daily life. At a time when the societal relevance of archaeology is under scrutiny more than ever before, the AHRC-funded Continuing Bonds Project – a collaboration between archaeology and palliative care – explores the potential of the past to promote discussion. Not only does archaeology illuminate the diversity of practice surrounding death, the past provides a safe, distanced platform for considering death, dying and bereavement today. Through archaeological and ethnographic case studies, health and social care professionals and students consider topics such as place, choice and identity, in both personal and professional life. This article examines participant responses to a variety of archaeological material and presents post-workshop reflections which demonstrate the success of archaeology in opening up conversations and increasing confidence in discussing this most enduring and problematic of life events.
  • Determination of contamination by polycyclic aromatic hydrocarbons, and their mode of origin, in urban soils from Leeds (UK)

    Hamed, Heiam A. Mohamed; Hale, William H.G.; Stern, Ben (2018-06)
    This study aims to determine the concentration of 16 Polycyclic Aromatic Hydrocarbons (PAHs) in urban soils from Leeds in order to determine what the factors are controlling their distribution and abundances. Soil samples were collected across an area from Leeds. Gas chromatography with mass spectrometry (GC-MS) using selected ion monitoring (SIM) was used to identify and quantify PAHs in the soil samples with the aid of PAH external standards. The results showed the highest concentrations of total PAHs in sample L8 (1344 ng/g) taken from an area located near a parking site and road in Leeds and the lowest total concentration of the 16 PAHs in sample L16 (87 ng/g) taken from a private garden. The ratio of anthracene to anthracene plus phenanthrene AN/(AN + PH), fluoranthene to fluoranthene plus pyrene FLU/(PY+FLU) and benzo[a]anthracene to 228 (BaA/228) implied that the PAHs pollution originated from pyrogenic, biomass and petroleum combustion in the samples which were collected from Leeds city.
  • Control of the stereochemistry of C14 hydroxyl during the total synthesis of withanolide E and physachenolide C

    Anees, Muhammad; Nayak, Sanjit; Afarinkia, Kamya; Vinader, Victoria (2018-11)
    The stereochemical outcome of the epoxidation of Δ14–15 cholestanes with mCPBA is controlled by the steric bulk of a C17 substituent. When the C17 is in the β configuration, the epoxide is formed in the α face, whereas if the C17 is trigonal (flat) or the substituent is in the α configuration, the epoxide is formed in the β face. The presence of a hydroxyl substituent at C20 does not influence the stereochemical outcome of the epoxidation.
  • Eicosapentaenoic acid and aspirin, alone and in combination, for the prevention of colorectal adenomas (seAFOod Polyp Prevention trial): a multicentre, randomised, double-blind, placebo-controlled, 2 × 2 factorial trial

    Hull, M.A.; Sprange, K.; Hepburn, T.; Tan, W.; Shafayat, A.; Rees, C.J.; Clifford, G.; Logan, R.F.; Loadman, Paul M.; Williams, E.A.; Whitham, D.; Montgomery, A.A. (2018-11-19)
    Background: The omega-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA) and aspirin both have proof of concept for colorectal cancer chemoprevention, aligned with an excellent safety profile. Therefore, we aimed to test the efficacy of EPA and aspirin, alone and in combination and compared with a placebo, in individuals with sporadic colorectal neoplasia detected at colonoscopy. Methods: In a multicentre, randomised, double-blind, placebo-controlled, 2 × 2 factorial trial, patients aged 55–73 years who were identified during colonoscopy as being at high risk in the English Bowel Cancer Screening Programme (BCSP; ≥3 adenomas if at least one was ≥10 mm in diameter or ≥5 adenomas if these were <10 mm in diameter) were recruited from 53 BCSP endoscopy units in England, UK. Patients were randomly allocated (1:1:1:1) using a secure web-based server to receive 2 g EPA-free fatty acid (FFA) per day (either as the FFA or triglyceride), 300 mg aspirin per day, both treatments in combination, or placebo for 12 months using random permuted blocks of randomly varying size, and stratified by BCSP site. Research staff and participants were masked to group assignment. The primary endpoint was the adenoma detection rate (ADR; the proportion of participants with any adenoma) at 1 year surveillance colonoscopy analysed in all participants with observable follow-up data using a so-called at-the-margins approach, adjusted for BCSP site and repeat endoscopy at baseline. The safety population included all participants who received at least one dose of study drug. The trial is registered with the International Standard Randomised Controlled Trials Number registry, number ISRCTN05926847. Findings: Between Nov 11, 2011, and June 10, 2016, 709 participants were randomly assigned to four treatment groups (176 to placebo, 179 to EPA, 177 to aspirin, and 177 to EPA plus aspirin). Adenoma outcome data were available for 163 (93%) patients in the placebo group, 153 (85%) in the EPA group, 163 (92%) in the aspirin group, and 161 (91%) in the EPA plus aspirin group. The ADR was 61% (100 of 163) in the placebo group, 63% (97 of 153) in the EPA group, 61% (100 of 163) in the aspirin group, and 61% (98 of 161) in the EPA plus aspirin group, with no evidence of any effect for EPA (risk ratio [RR] 0·98, 95% CI 0·87 to 1·12; risk difference –0·9%, –8·8 to 6·9; p=0·81) or aspirin (RR 0·99 (0·87 to 1·12; risk difference –0·6%, –8·5 to 7·2; p=0·88). EPA and aspirin were well tolerated (78 [44%] of 176 had ≥1 adverse event in the placebo group compared with 82 [46%] in the EPA group, 68 [39%] in the aspirin group, and 76 [45%] in the EPA plus aspirin group), although the number of gastrointestinal adverse events was increased in the EPA alone group at 146 events (compared with 85 in the placebo group, 86 in the aspirin group, and 68 in the aspirin plus placebo group). Six upper-gastrointestinal bleeding events were reported across the treatment groups (two in the EPA group, three in the aspirin group, and one in the placebo group). Interpretation Neither EPA nor aspirin treatment were associated with a reduction in the proportion of patients with at least one colorectal adenoma. Further research is needed regarding the effect on colorectal adenoma number according to adenoma type and location. Optimal use of EPA and aspirin might need a precision medicine approach to adenoma recurrence.
  • Estimation of contrast sensitivity from fixational eye movements

    Denniss, Jonathan; Scholes, C.; McGraw, P.V.; Nam, S-H.; Roach, N.W. (2018-11)
    Purpose: Even during steady fixation, people make small eye movements such as microsaccades, whose rate is altered by presentation of salient stimuli. Our goal was to develop a practical method for objectively and robustly estimating contrast sensitivity from microsaccade rates in a diverse population. Methods: Participants, recruited to cover a range of contrast sensitivities, were visually normal (n = 19), amblyopic (n = 10), or had cataract (n = 9). Monocular contrast sensitivity was estimated behaviorally while binocular eye movements were recorded during interleaved passive trials. A probabilistic inference approach was used to establish the likelihood of observed microsaccade rates given the presence or absence of a salient stimulus. Contrast sensitivity was estimated from a function fitted to the scaled log-likelihood ratio of the observed microsaccades in the presence or absence of a salient stimulus across a range of contrasts. Results: Microsaccade rate signature shapes were heterogeneous; nevertheless, estimates of contrast sensitivity could be obtained in all participants. Microsaccade-estimated contrast sensitivity was unbiased compared to behavioral estimates (1.2% mean), with which they were strongly correlated (Spearman's ρ 0.74, P < 0.001, median absolute difference 7.6%). Measurement precision of microsaccade-based contrast sensitivity estimates was worse than that of behavioral estimates, requiring more than 20 times as many presentations to equate precision. Conclusions: Microsaccade rate signatures are heterogeneous in shape when measured across populations with a broad range of contrast sensitivities. Contrast sensitivity can be robustly estimated from rate signatures by probabilistic inference, but more stimulus presentations are currently required to achieve similarly precise estimates to behavioral techniques.

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