The missing N1 or jittered P2: Electrophysiological correlates of pattern glare in the time and frequency domain

Excessive sensitivity to certain visual stimuli (cortical hyperexcitability) is associated with a number of neurological disorders including migraine, epilepsy, multiple sclerosis, autism and possibly dyslexia. Others show disruptive sensitivity to visual stimuli with no other obvious pathology or symptom profile (visual stress) which can extend to discomfort and nausea. We used event-related potentials (ERPs) to explore the neural correlates of visual stress and headache proneness. We analysed ERPs in response to thick (0.37 cycles per degree [c/deg]), medium (3 c/deg) and thin (12 c/deg) gratings, using mass univariate analysis, considering three factors in the general population: headache proneness, visual stress and discomfort. We found relationships between ERP features and the headache and discomfort factors. Stimulus main effects were driven by the medium stimulus regardless of participant characteristics. Participants with high discomfort ratings had larger P1 components for the initial presentation of medium stimuli, suggesting initial cortical hyperexcitability that is later suppressed. The participants with high headache ratings showed atypical N1-P2 components for medium stripes relative to the other stimuli. This effect was present only after repeated stimulus presentation. These effects were also explored in the frequency domain, suggesting variations in intertrial theta band phase coherence. Our results suggest that discomfort and headache in response to striped stimuli are related to different neural processes; however, more exploration is needed to determine whether the results translate to a clinical migraine population

SQL Tester: An online SQL assessment tool and its impact

Learning SQL can be surprisingly difficult, given the relative simplicity of its syntax. Automated tools for teaching and assessing SQL have existed for over two decades. Early tools were only designed for teaching and offered increased feedback and personalised learning, but not summative assessment. More recently, however, the trend has turned towards automated assessment, with learning as a side-effect. These tools offer more limited feedback and are not personalised. In this paper, we present SQL Tester, an online assessment tool and an assessment of its impact. We show that students engaged with SQL Tester as a learning tool, taking an average of 10 practice tests each and spending over 4 hours actively engaged in those tests. A student survey also found that over 90% of students agreed that they wanted to keep trying practice tests until they got a “good” mark. Finally, we present some evidence that taking practice tests increased student achievement, with a strong correlation between the number of practice tests a student took and their score on the assessed test

Participation in Free and Open Source Communities: An Empirical Study of Community Members’ Perceptions

Although the defining factors of Free and Open Source Software (FOSS) are generally seen as the availability and accessibility of the source code, it is what these facilitate that is perhaps of more significance. Source code availability allows the sharing of code, skills, knowledge, and effort, focused on a particular piece of software under development. The result of this is the FOSS community, which although often perceived as a single group, is actually many small groups, each bound by a common interest in a particular piece of software and using the Internet as a communication medium. Although there have been studies focusing on the motivation of FOSS developers to contribute to software, there has been little investigation into the motives, attitudes, and the culture within the communities as a whole. There is much more to most of these communities than software development. Many also have extensive support networks for the use of software, portals for research, and social facilities. This paper describes the results of an investigation into how FOSS community members perceive the communities that they belong to, their reasons for being in the community, and the manner in which they participate

Reduced sensitivity for visual textures affects judgments of shape-from-shading and step climbing behaviour in older adults

Falls on stairs are a major hazard for older adults. Visual decline in normal aging can affect step climbing ability, altering gait and reducing toe clearance. Here we show that a loss of fine-grained visual information associated with age can affect the perception of surface undulations in patterned surfaces. We go on to show that such cues affect the limb trajectories of young adults, but due to their lack of sensitivity, not that of older adults. Interestingly neither the perceived height of a step nor conscious awareness are altered by our visual manipulation but stepping behaviour is: suggesting that the influence of shape perception on stepping behaviour is via the unconscious, action-centred, dorsal visual pathway

Natural variants modify Klebsiella pneumoniae carbapenemase (KPC) acyl-enzyme conformational dynamics to extend antibiotic resistance

Class A serine β-lactamases (SBLs) are key antibiotic resistance determinants in Gram-negative bacteria. SBLs neutralize β-lactams via a hydrolytically labile covalent acyl-enzyme intermediate. Klebsiella pneumoniae carbapenemase (KPC) is a widespread SBL that hydrolyzes carbapenems, the most potent β-lactams; known KPC variants differ in turnover of expanded-spectrum oxyimino-cephalosporins (ESOCs), for example, cefotaxime and ceftazidime. Here, we compare ESOC hydrolysis by the parent enzyme KPC-2 and its clinically observed double variant (P104R/V240G) KPC-4. Kinetic analyses show that KPC-2 hydrolyzes cefotaxime more efficiently than the bulkier ceftazidime, with improved ESOC turnover by KPC-4 resulting from enhanced turnover (k<sub>cat</sub>), rather than altered K<sub>M</sub> values. High-resolution crystal structures of ESOC acyl-enzyme complexes with deacylation-deficient (E166Q) KPC-2 and KPC-4 mutants show that ceftazidime acylation causes rearrangement of three loops; the Ω, 240, and 270 loops, which border the active site. However, these rearrangements are less pronounced in the KPC-4 than the KPC-2 ceftazidime acyl-enzyme and are not observed in the KPC-2:cefotaxime acyl-enzyme. Molecular dynamics simulations of KPC:ceftazidime acyl-enyzmes reveal that the deacylation general base E166, located on the Ω loop, adopts two distinct conformations in KPC-2, either pointing "in" or "out" of the active site; with only the "in" form compatible with deacylation. The "out" conformation was not sampled in the KPC-4 acyl-enzyme, indicating that efficient ESOC breakdown is dependent upon the ordering and conformation of the KPC Ω loop. The results explain how point mutations expand the activity spectrum of the clinically important KPC SBLs to include ESOCs through their effects on the conformational dynamics of the acyl-enzyme intermediate

Effect of the Dielectric-Constant Mismatch and Magnetic Field on the Binding Energy of Hydrogenic Impurities in a Spherical Quantum Dot

Within the effective mass approximation and variational method the effect of dielectric constant mismatch between the size-quantized semiconductor sphere, coating and surrounding environment on impurity binding energy in both the absence and presence of a magnetic field is considered. The dependences of the binding energy of a hydrogenic on-center impurity on the sphere and coating radii, alloy concentration, dielectric-constant mismatch, and magnetic field intensity are found for the GaAs-Ga_(1-x)Al_(x)As-AlAs (or vacuum) system

Nonlinear spectra of spinons and holons in short GaAs quantum wires.

One-dimensional electronic fluids are peculiar conducting systems, where the fundamental role of interactions leads to exotic, emergent phenomena, such as spin-charge (spinon-holon) separation. The distinct low-energy properties of these 1D metals are successfully described within the theory of linear Luttinger liquids, but the challenging task of describing their high-energy nonlinear properties has long remained elusive. Recently, novel theoretical approaches accounting for nonlinearity have been developed, yet the rich phenomenology that they predict remains barely explored experimentally. Here, we probe the nonlinear spectral characteristics of short GaAs quantum wires by tunnelling spectroscopy, using an advanced device consisting of 6000 wires. We find evidence for the existence of an inverted (spinon) shadow band in the main region of the particle sector, one of the central predictions of the new nonlinear theories. A (holon) band with reduced effective mass is clearly visible in the particle sector at high energies.This work was supported by the UK EPSRC [Grant Nos. EP/J01690X/1 and EP/J016888/1].This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/NCOMMS12784

Measuring commissioners’ willingness-to-pay for community based childhood obesity prevention programmes using a discrete choice experiment

Background: In the UK, rates of childhood obesity remain high. Community based programmes for child obesity prevention are available to be commissioned by local authorities. However, there is a lack of evidence regarding how programmes are commissioned and which attributes of programmes are valued most by commissioners. The aim of this study was to determine the factors that decision-makers prioritise when commissioning programmes that target childhood obesity prevention. Methods: An online discrete choice experiment (DCE) was used to survey commissioners and decision makers in the UK to assess their willingness-to-pay for childhood obesity programmes. Results: A total of 64 commissioners and other decision makers completed the DCE. The impact of programmes on behavioural outcomes was prioritised, with participants willing to pay an extra £16,600/year if average daily fruit and vegetable intake increased for each child by one additional portion. Participants also prioritised programmes that had greater number of parents fully completing them, and were willing to pay an extra £4810/year for every additional parent completing a programme. The number of parents enrolling in a programme (holding the number completing fixed) and hours of staff time required did not significantly influence choices. Conclusions: Emphasis on high programme completion rates and success increasing children’s fruit and vegetable intake has potential to increase commissioning of community based obesity prevention programmes