808 research outputs found

    Cross-bispectrum computation and variance estimation

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    A method for the estimation of cross-bispectra of discrete real time series is developed. The asymptotic variance properties of the bispectrum are reviewed, and a method for the direct estimation of bispectral variance is given. The symmetry properties are described which minimize the computations necessary to obtain a complete estimate of the cross-bispectrum in the right-half-plane. A procedure is given for computing the cross-bispectrum by subdividing the domain into rectangular averaging regions which help reduce the variance of the estimates and allow easy application of the symmetry relationships to minimize the computational effort. As an example of the procedure, the cross-bispectrum of a numerically generated, exponentially distributed time series is computed and compared with theory

    Estimating three-demensional energy transfer in isotropic turbulence

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    To obtain an estimate of the spectral transfer function that indicates the rate of decay of energy, an x-wire probe was set at a fixed position, and two single wire probes were set at a number of locations in the same plane perpendicular to the mean flow in the wind tunnel. The locations of the single wire probes are determined by pseudo-random numbers (Monte Carlo). Second order spectra and cross spectra are estimated. The assumption of isotropy relative to second order spectra is examined. Third order spectra are also estimated corresponding to the positions specified. A Monte Carlo Fourier transformation of the downstream bispectra corresponding to integration across the plane perpendicular to the flow is carried out assuming isotropy. Further integration is carried out over spherical energy shells

    Arachnoid cysts do not contain cerebrospinal fluid: A comparative chemical analysis of arachnoid cyst fluid and cerebrospinal fluid in adults

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    <p>Abstract</p> <p>Background</p> <p>Arachnoid cyst (AC) fluid has not previously been compared with cerebrospinal fluid (CSF) from the same patient. ACs are commonly referred to as containing "CSF-like fluid". The objective of this study was to characterize AC fluid by clinical chemistry and to compare AC fluid to CSF drawn from the same patient. Such comparative analysis can shed further light on the mechanisms for filling and sustaining of ACs.</p> <p>Methods</p> <p>Cyst fluid from 15 adult patients with unilateral temporal AC (9 female, 6 male, age 22-77y) was compared with CSF from the same patients by clinical chemical analysis.</p> <p>Results</p> <p>AC fluid and CSF had the same osmolarity. There were no significant differences in the concentrations of sodium, potassium, chloride, calcium, magnesium or glucose. We found significant elevated concentration of phosphate in AC fluid (0.39 versus 0.35 mmol/L in CSF; <it>p </it>= 0.02), and significantly reduced concentrations of total protein (0.30 versus 0.41 g/L; <it>p </it>= 0.004), of ferritin (7.8 versus 25.5 ug/L; <it>p </it>= 0.001) and of lactate dehydrogenase (17.9 versus 35.6 U/L; <it>p </it>= 0.002) in AC fluid relative to CSF.</p> <p>Conclusions</p> <p>AC fluid is not identical to CSF. The differential composition of AC fluid relative to CSF supports secretion or active transport as the mechanism underlying cyst filling. Oncotic pressure gradients or slit-valves as mechanisms for generating fluid in temporal ACs are not supported by these results.</p

    LOW CYCLE FATIGUE OF T-TUBULAR JOINTS WITH OUT-OF-PLANE BENDING LOADING

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    ABSTRACT Tubular T-joints were fatigue tested with out-of-plane bending loading. Six models were tested, three models with Rratio of 0 and three with R = -1. Hot spot stress was measured for the brace and for the chord using the ECSC linear extrapolation procedure. Fatigue loading was applied in load control, to obtain through thickness cracking at a number of cycles in the range 4 000 -200 000 cycles. The data were analysed and compared with published data and with current fatigue design criteria for tubular joints. INTRODUCTION Fatigue loading on tubular offshore structures is predominately wave loading. For a design life of 20 years the number of cycles is of the order of 10 8 and the major contribution to the cumulative damage is from stress ranges corresponding to a constant amplitude life above 10 5 cycles. For this reason design SN curves for tubular joints are based on fatigue tests in the high cycle range, i.e. in the range 10 5 -1

    Line managers' middle-levelness and driving proactive behaviors in organizational interventions

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    Purpose: This paper explores line managers' proactive work behaviors in organizational interventions and ascertains how their management of their middle-levelness by aligning with the intervention, or not, influences their proactive work behaviors. Design/methodology/approach: The authors’ findings are based on thematic analysis of 20 semi-structured interviews of university heads of departments responsible for managing organizational interventions. Findings: The authors found that line managers engaged in a range of proactive work behaviors to implement the organizational intervention (i.e. “driving proactive behaviors”). Furthermore, line managers tended to engage in driving proactive behaviors when they aligned with the organizational intervention, but not to when unconvinced of the intervention's validity. Practical implications: These findings highlight the importance of senior management and HR investing sufficient time and quality in the preparation phase to ensure all actors have a shared understanding of the organizational interventions' validity. Originality/value: This is the first study to explore line managers' proactive work behaviors to implement an organizational intervention, and how the line managers' management of their middle-levelness influence these proactive work behaviors

    The Methylococcus capsulatus (Bath) Secreted Protein, MopE*, Binds Both Reduced and Oxidized Copper

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    Under copper limiting growth conditions the methanotrophic bacterium Methylococcus capsulatus (Bath) secrets essentially only one protein, MopE*, to the medium. MopE* is a copper-binding protein whose structure has been determined by X-ray crystallography. The structure of MopE* revealed a unique high affinity copper binding site consisting of two histidine imidazoles and one kynurenine, the latter an oxidation product of Trp130. In this study, we demonstrate that the copper ion coordinated by this strong binding site is in the Cu(I) state when MopE* is isolated from the growth medium of M. capsulatus. The conclusion is based on X-ray Near Edge Absorption spectroscopy (XANES), and Electron Paramagnetic Resonance (EPR) studies. EPR analyses demonstrated that MopE*, in addition to the strong copper-binding site, also binds Cu(II) at two weaker binding sites. Both Cu(II) binding sites have properties typical of non-blue type II Cu (II) centres, and the strongest of the two Cu(II) sites is characterised by a relative high hyperfine coupling of copper (

    Safety representatives’ job crafting in organizational interventions: driver, counselor, watchdog, or abstainer

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    The Nordic model and organizational research highlight the benefits of employee participation and collaboration between management and employees. Using job crafting theory, this paper studied the roles safety representatives craft for themselves in organizational interventions, the mental models that impact the roles they craft, and the possible consequences these roles have for intervention implementation. The research used a case study design to interview 15 safety representatives of 15 different departments at a university in Norway regarding their role in an organizational intervention. The thematic analysis identified five roles the safety representatives crafted for themselves: 1) Watchdogs safeguarding the work environment, 2) Watchdogs safeguarding the line managers’ implementation, 3) Counsellors to the line manager on how to implement the intervention activities, 4) Drivers who themselves implement the intervention activities, and 5) Abstainers who let the intervention occur without their involvement. The safety representatives’ mental models of their line manager, the work environment, their colleagues, and the intervention itself appeared to affect the roles they crafted. Finally, the different roles safety representatives crafted for themselves seemed to influence the intervention implementation

    Reading acceleration training changes brain circuitry in children with reading difficulties

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    Introduction: Dyslexia is characterized by slow, inaccurate reading. Previous studies have shown that the Reading Acceleration Program (RAP) improves reading speed and accuracy in children and adults with dyslexia and in typical readers across different orthographies. However, the effect of the RAP on the neural circuitry of reading has not been established. In the current study, we examined the effect of the RAP training on regions of interest in the neural circuitry for reading using a lexical decision task during fMRI in children with reading difficulties and typical readers. Methods: Children (8–12 years old) with reading difficulties and typical readers were studied before and after 4 weeks of training with the RAP in both groups. Results: In addition to improvements in oral and silent contextual reading speed, training-related gains were associated with increased activation of the left hemisphere in both children with reading difficulties and typical readers. However, only children with reading difficulties showed improvements in reading comprehension, which were associated with significant increases in right frontal lobe activation. Conclusions: Our results demonstrate differential effects of the RAP on neural circuits supporting reading in both children with reading difficulties and typical readers and suggest that the intervention may stimulate use of typical neural circuits for reading and engage compensatory pathways to support reading in the developing brain of children with reading difficulties

    Temporal fossa arachnoid cyst presenting with bilateral subdural hematoma following trauma: two case reports

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    <p>Abstract</p> <p>Introduction</p> <p>Intracranial arachnoid cysts are considered to be congenital malformations with a predilection for the temporal fossa. They are often asymptomatic but can sometimes be symptomatic due to enlargement or hemorrhage. There are multiple case reports of arachnoid cysts becoming symptomatic with hemorrhagic complications following head trauma. In such cases, the bleeding is often confined to the side ipsilateral to the arachnoid cyst. Occurrence of contralateral subdural hematomas in patients with temporal fossa arachnoid cysts has rarely been observed and is reported less frequently in the medical literature.</p> <p>Case presentation</p> <p>We report two cases of people (a 23-year-old man and a 41-year-old man) with temporal fossa arachnoid cysts complicated by a subdural hematoma following head injury. Both patients developed a subdural hematoma contralateral to the side of a temporal fossa arachnoid cyst. It is likely that lack of adequate intracranial cushioning in the presence of an intracranial arachnoid cyst may result in injury not only to ipsilateral but also to contralateral bridging veins, following head trauma.</p> <p>Conclusion</p> <p>It is important to identify and report such rare complications with intracranial arachnoid cysts, so that asymptomatic patients with an intracranial arachnoid cyst can be counseled about such possibilities following head trauma.</p
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