Comparison of Neural Network Error Measures for Simulation of Slender Marine Structures

Training of an artificial neural network (ANN) adjusts the internal weights of the network in order to minimize a predefined error measure. This error measure is given by an error function. Several different error functions are suggested in the literature. However, the far most common measure for regression is the mean square error. This paper looks into the possibility of improving the performance of neural networks by selecting or defining error functions that are tailor-made for a specific objective. A neural network trained to simulate tension forces in an anchor chain on a floating offshore platform is designed and tested. The purpose of setting up the network is to reduce calculation time in a fatigue life analysis. Therefore, the networks trained on different error functions are compared with respect to accuracy of rain flow counts of stress cycles over a number of time series simulations. It is shown that adjusting the error function to perform significantly better on a specific problem is possible. On the other hand. it is also shown that weighted error functions actually can impair the performance of an ANN

Visual function in Norwegian children aged 5–13 years with prenatal exposure to opioid maintenance therapy: A case–control study

Purpose: To assess various aspects of visual function in school children prenatally exposed to opioid maintenance therapy (OMT) and to explore possible outcome differences between prenatal methadone and buprenorphine exposure. Methods: In a cross-sectional case–control study, 63 children aged 5–13 years with prenatal OMT exposure were compared with 63 age- and gender-matched, non-exposed controls regarding important visual parameters, such as visual acuity, orthoptic status, refractive state, colour vision, and visual field. Results: The OMT-exposed children had significantly poorer visual acuity, both for the best eye, the worst eye and binocularly. Two children had mild visual impairment. Manifest strabismus was more frequent in the OMT group, 30%, vs. 4.8% in the control group. The most frequent types of strabismus were accommodative esotropia and intermittent exotropia. Manifest nystagmus was present in 10 (16%) of the exposed children compared to one among the non-exposed children. The accommodative amplitude was decreased in the OMT group compared to the controls. After adjusting for polydrug exposure and SGA (small-for-gestational-age), the between-group differences in visual acuity, strabismus, and nystagmus remained. The methadone-exposed children had poorer visual acuity, increased frequency of strabismus and a higher percentage of nystagmus, hypermetropia and astigmatism compared to the buprenorphine-exposed children. Conclusions: School-age children exposed to methadone or buprenorphine in utero had a higher prevalence of strabismus and nystagmus, and a lower visual acuity and accommodation amplitude. Buprenorphine exposure was associated with more favourable results than methadone exposure on most visual outcome measures and should be the preferred substance in OMT.publishedVersio

Transcranial sonothrombolysis using high-intensity focused ultrasound: impact of increasing output power on clot fragmentation

Abstract Background The primary goal of this study was to investigate the relationship between increasing output power levels and clot fragmentation during high-intensity focused ultrasound (HIFU)-induced thrombolysis. Methods A HIFU headsystem, designed for brain applications in humans, was used for this project. A human calvarium was mounted inside the water-filled hemispheric transducer. Artificial thrombi were placed inside the skull and located at the natural focus point of the transducer. Clots were exposed to a range of acoustic output power levels from 0 to 400 W. The other HIFU operating parameters remained constant. To assess clot fragmentation, three filters of different mesh pore sizes were used. To assess sonothrombolysis efficacy, the clot weight loss was measured. Results No evidence of increasing clot fragmentation was found with increasing acoustic intensities in the majority of the study groups of less than 400 W. Increasing clot lysis could be observed with increasing acoustic output powers. Conclusion Transcranial sonothrombolysis could be achieved in vitro within seconds in the absence of tPA and without producing relevant clot fragmentation, using acoustic output powers of \u3c400 W

Quantitative X-ray Tomography of the Mouse Cochlea

Imaging with hard X-rays allows visualizing cochlear structures while maintaining intrinsic qualities of the tissue, including structure and size. With coherent X-rays, soft tissues, including membranes, can be imaged as well as cells making use of the so-called in-line phase contrast. In the present experiments, partially coherent synchrotron radiation has been used for micro-tomography. Three-dimensional reconstructions of the mouse cochlea have been created using the EM3D software and the volume has been segmented in the Amira Software Suite. The structures that have been reconstructed include scala tympani, scala media, scala vestibuli, Reissner's membrane, basilar membrane, tectorial membrane, organ of Corti, spiral limbus, spiral ganglion and cochlear nerve. Cross-sectional areas of the scalae were measured. The results provide a realistic and quantitative reconstruction of the cochlea

Resolution of Ultramicroscopy and Field of View Analysis

In a recent publication we described a microscopical technique called Ultramicroscopy, combined with a histological procedure that makes biological samples transparent. With this combination we can gather three-dimensional image data of large biological samples. Here we present the theoretical analysis of the z-resolution. By analyzing the cross-section of the illuminating sheet of light we derive resolution values according to the Rayleigh-criterion. Next we investigate the resolution adjacent to the focal point of the illumination beam, analyze throughout what extend the illumination beam is of acceptable sharpness and investigate the resolution improvements caused by the objective lens. Finally we conclude with a useful rule for the sampling rates. These findings are of practical importance for researchers working with Ultramicroscopy to decide on adequate sampling rates. They are also necessary to modify deconvolution techniques to gain further image improvements

Meningitis due to Fusobacterium necrophorum in an adult

BACKGROUND: Fusobacterium necrophorum may cause a number of clinical syndromes, collectively known as necrobacillosis. Meningitis is a significant cause of mortality, rarely reported in the adult population. CASE PRESENTATION: We report a fatal case of meningitis, caused by Fusobacterium necrophorum, secondary to otitis media in an alcoholic male. Diagnosis was delayed due to the typical slow growth of the organism. The clinical course was complicated by encephalitis and by hydrocephalus. The patient failed to respond to metronidazole and penicillin. The patient died on day 12 from increased intracranial pressure and brain stem infarction. CONCLUSIONS: This case emphasizes the need for a high index of clinical suspicion to make the diagnosis of Fusobacterium necrophorum meningitis. We recommend the use of appropriate anaerobic culture techniques and antimicrobial coverage for anaerobic organisms when the gram stain shows gram negative bacilli

Light Sheet Microscopy for Single Molecule Tracking in Living Tissue

Single molecule observation in cells and tissue allows the analysis of physiological processes with molecular detail, but it still represents a major methodological challenge. Here we introduce a microscopic technique that combines light sheet optical sectioning microscopy and ultra sensitive high-speed imaging. By this approach it is possible to observe single fluorescent biomolecules in solution, living cells and even tissue with an unprecedented speed and signal-to-noise ratio deep within the sample. Thereby we could directly observe and track small and large tracer molecules in aqueous solution. Furthermore, we demonstrated the feasibility to visualize the dynamics of single tracer molecules and native messenger ribonucleoprotein particles (mRNPs) in salivary gland cell nuclei of Chironomus tentans larvae up to 200 µm within the specimen with an excellent signal quality. Thus single molecule light sheet based fluorescence microscopy allows analyzing molecular diffusion and interactions in complex biological systems

Cryptococcus neoformans Intracellular Proliferation and Capsule Size Determines Early Macrophage Control of Infection.

Cryptococcus neoformans is a significant fungal pathogen of immunocompromised patients. Many questions remain regarding the function of macrophages in normal clearance of cryptococcal infection and the defects present in uncontrolled cryptococcosis. Two current limitations are: 1) The difficulties in interpreting studies using isolated macrophages in the context of the progression of infection, and 2) The use of high resolution imaging in understanding immune cell behavior during animal infection. Here we describe a high-content imaging method in a zebrafish model of cryptococcosis that permits the detailed analysis of macrophage interactions with C. neoformans during infection. Using this approach we demonstrate that, while macrophages are critical for control of C. neoformans, a failure of macrophage response is not the limiting defect in fatal infections. We find phagocytosis is restrained very early in infection and that increases in cryptococcal number are driven by intracellular proliferation. We show that macrophages preferentially phagocytose cryptococci with smaller polysaccharide capsules and that capsule size is greatly increased over twenty-four hours of infection, a change that is sufficient to severely limit further phagocytosis. Thus, high-content imaging of cryptococcal infection in vivo demonstrates how very early interactions between macrophages and cryptococci are critical in the outcome of cryptococcosis