71 research outputs found
Tsunami response in semienclosed tidal basins using an aggregated model
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of American Society of Civil Engineers for personal use, not for redistribution. The definitive version was published in Journal of Hydraulic Engineering 138 (2012): 744–751, doi:10.1061/(ASCE)HY.1943-7900.0000573.An aggregated model to evaluate tsunami response in semi-enclosed water bodies is
presented in this work. The model is based on one-dimensional shallow water equations
and can include long-wave external forcing such as a tsunami. It has been successfully
validated against experimental data from a physical model, and its predictions for a case
study have been compared with results from the COMCOT numerical model. The model
can be used as a predictive tool because a calibration using a theoretical value for
expansion and contraction losses has been performed, and differences with the typical
calibration are less than 10% which is considered acceptable. This allows using the model
in the absence of measured data, which is very difficult to obtain in case of a tsunami
event. A case study for the Gulf of Cádiz (Spain) has been simulated with the COMCOT
model. The aggregated model predicted the response for a harbor more accurately than
for estuarine systems with tidal flats. Nevertheless, the aggregated model has been
demonstrated as a useful general tool to predict the response of semi-enclosed tidal basins
to a tsunami event, and hybrid models coupling advanced models to simulate ocean
tsunami propagation with the model presented here would be useful in developing coastal
warning alert systems
The role of intratidal oscillations in sediment resuspension in a diurnal, partially mixed estuary
Using detailed observations of the mean and turbulent properties of flow, salinity and turbidity that spanned 2001/02, we examined the physical mechanisms underpinning sediment resuspension in the low-energy Swan River estuary, Western Australia. In this diurnal tidally-dominated estuary, the presence of intratidal oscillations, a tidal inequality lasting 2 to 3 hours on the flood tide, generated by interactions of the four main diurnal and semidiurnal astronomical constituents, K₁, O₁, M₂, and S₂, played a major role in modifying vertical stratification and mixing. These intratidal oscillations are controlled by phase differences between the tropic and synodic months rather than being temporally-fixed by bed friction, as occurs in semidiurnal estuaries. Intratidal oscillations are largest, at around 0.1 m, near to the Austral solstice when the lunar and solar declination are in-phase. Despite the seemingly small change in water level, shear-induced interfacial mixing caused destratification of the water column with the top-to-bottom salinity (ΔS) difference of 3.5 present early in the flood tide eroded to less than 0.3 by the end of the intratidal oscillation. High turbidity peaks, of 250 nephelometric turbidity units, coincided with these intratidal oscillations and could not be explained by bed friction since shear stress from mean flow did not exceed threshold criteria. High Reynolds stresses of ∼1 Nm⁻² did, however, exceed τcr and together with negative Reynolds fluxes indicate a net downward transport of material. Destratification of the water column induced by shear instabilities resulted in large overturns capable of moving in situ material towards the bed during intratidal oscillations and these turbidities were ∼10 times greater than those from bed-generated resuspension observed later during the flood tide
A framework for the discovery of retinal biomarkers in Optical Coherence Tomography Angiography (OCTA)
Juxta-articular myxoma of the knee in a 5-year-old boy: a case report and review of the literature (2009: 12b)
Juxta-articular myxoma (JAM) is a relatively rare variant of myxoma that occurs in the vicinity of large joints. It is composed of fibroblast-like cells that produce an excessive amount of glycosaminoglycans rich in hyaluronic acid. The peak incidence is between the 3rd and 5th decades of life. In this report we describe an extremely rare case of JAM in the knee of a 5-year-old child. The clinical presentation, radiological features and histopathologic findings are described, and the relevant literature is reviewed
Retinal and Cerebral Microvasculopathy: Relationships and Their Genetic Contributions
PURPOSE: Retinal microvasculopathy may reflect small vessel disease in the brain. Here we test
the relationships between retinal vascular parameters and small vessel disease, the influence
of cardiovascular risk factors on these relationships, and their common genetic background in
a monozygotic twin cohort.
METHODS: We selected 134 cognitively healthy individuals (67 monozygotic twin pairs) aged
‡60 years from the Netherlands Twin Register for the EMIF-AD PreclinAD study. We measured
seven retinal vascular parameters averaged over both eyes using fundus images analyzed with
Singapore I Vessel Assessment. Small vessel disease was assessed on MRI by a volumetric
measurement of periventricular and deep white matter hyperintensities. We calculated
associations between RVPs and WMH, estimated intratwin pair correlations, and performed
twin-specific analyses on relationships of interest.
RESULTS: Deep white matter hyperintensities volume was positively associated with retinal
tortuosity in veins (P ¼ 0.004) and fractal dimension in arteries (P ¼ 0.001) and veins (P ¼
0.032), periventricular white matter hyperintensities volume was positively associated with
retinal venous width (P ¼ 0.028). Intratwin pair correlations were moderate to high for all
small vessel disease/retinal vascular parameter variables (r ¼ 0.49–0.87, P < 0.001). Crosstwin
cross-trait analyses showed that retinal venous tortuosity of twin 1 could predict deep
white matter hyperintensities volume of the co-twin (r ¼ 0.23, P ¼ 0.030). Within twin-pair
differences for retinal venous tortuosity were associated with within twin-pair differences in
deep white matter hyperintensities volume (r ¼ 0.39, P ¼ 0.001).
CONCLUSIONS: Retinal arterial fractal dimension and venous tortuosity have associations with
deep white matter hyperintensities volume. Twin-specific analyses suggest that retinal venous
tortuosity and deep white matter hyperintensities volume have a common etiology driven by
both shared genetic factors and unique environmental factors, supporting the robustness of
this relationship
Resilience to cognitive impairment in the oldest-old: design of the EMIF-AD 90+ study
BACKGROUND: The oldest-old (subjects aged 90 years and older) population represents the fastest growing segment of society and shows a high dementia prevalence rate of up to 40%. Only a few studies have investigated protective factors for cognitive impairment in the oldest-old. The EMIF-AD 90+ Study aims to identify factors associated with resilience to cognitive impairment in the oldest-old. In this paper we reviewed previous studies on cognitive resilience in the oldest-old and described the design of the EMIF-AD 90+ Study. METHODS: The EMIF-AD 90+ Study aimed to enroll 80 cognitively normal subjects and 40 subjects with cognitive impairment aged 90 years or older. Cognitive impairment was operationalized as amnestic mild cognitive impairment (aMCI), or possible or probable Alzheimer's Disease (AD). The study was part of the European Medical Information Framework for AD (EMIF-AD) and was conducted at the Amsterdam University Medical Centers (UMC) and at the University of Manchester. We will test whether cognitive resilience is associated with cognitive reserve, vascular comorbidities, mood, sleep, sensory system capacity, physical performance and capacity, genetic risk factors, hallmarks of ageing, and markers of neurodegeneration. Markers of neurodegeneration included an amyloid positron emission tomography, amyloid β and tau in cerebrospinal fluid/blood and neurophysiological measures. DISCUSSION: The EMIF-AD 90+ Study will extend our knowledge on resilience to cognitive impairment in the oldest-old by extensive phenotyping of the subjects and the measurement of a wide range of potential protective factors, hallmarks of aging and markers of neurodegeneration. TRIAL REGISTRATION: Nederlands Trial Register NTR5867 . Registered 20 May 2016
The EMIF-AD PreclinAD study: study design and baseline cohort overview
BACKGROUND: Amyloid pathology is the pathological hallmark in Alzheimer’s disease (AD) and can precede clinical
dementia by decades. So far it remains unclear how amyloid pathology leads to cognitive impairment and dementia.
To design AD prevention trials it is key to include cognitively normal subjects at high risk for amyloid pathology and to
find predictors of cognitive decline in these subjects. These goals can be accomplished by targeting twins, with
additional benefits to identify genetic and environmental pathways for amyloid pathology, other AD biomarkers,
and cognitive decline.
METHODS: From December 2014 to October 2017 we enrolled cognitively normal participants aged 60 years and
older from the ongoing Manchester and Newcastle Age and Cognitive Performance Research Cohort and the
Netherlands Twins Register. In Manchester we included single individuals, and in Amsterdam monozygotic twin
pairs. At baseline, participants completed neuropsychological tests and questionnaires, and underwent physical
examination, blood sampling, ultrasound of the carotid arteries, structural and resting state functional brain magnetic
resonance imaging, and dynamic amyloid positron emission tomography (PET) scanning with [18F]flutemetamol. In
addition, the twin cohort underwent lumbar puncture for cerebrospinal fluid collection, buccal cell collection,
magnetoencephalography, optical coherence tomography, and retinal imaging.
RESULTS: We included 285 participants, who were on average 74.8 ± 9.7 years old, 64% female. Fifty-eight participants
(22%) had an abnormal amyloid PET scan.
CONCLUSIONS: A rich baseline dataset of cognitively normal elderly individuals has been established to estimate risk
factors and biomarkers for amyloid pathology and future cognitive declin
Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework
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