Collections of art on paper, libraries and archives in general, are striving for optimal storage conditions for cultural heritage in their deposits and exhibition facilities. Therefore, properly ...estimating the risk of volatile organic compounds emitted from historic and recent storage materials on paper-based collections is of utmost importance. Applying an optimized static headspace gas chromatography and mass spectrometry approach combined with cellulose-specific analysis provides insight into the potential degradation effects and mechanisms acting on two different paper samples (Whatman No.1 and historic rag paper) used as degradation indicators. Acetic and formic acid, two powerful volatile organic acids, were quantified with differing amounts, depending on the type of historic storage material tested. Molar mass and carbonyl group content were used to monitor cellulose degradation of the indicator papers. Combining these results in 3D plots helps to visualize synergies that evolve from mutual emission of acetic and formic acids. In addition, choosing between the two paper-based degradation indicators helps to evaluate different phenomena: Whatman No.1 reacts toward acid hydrolysis and is more sensitive, while rag paper helps to evaluate buffering phenomena as occurring in original materials.
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The placement of a percutaneous endoscopic gastrostomy (PEG) in a patient with a pre-existing ventriculoperitoneal shunt is generally regarded as safe. A critical but often overlooked technical ...consideration is confirmation of the course of the distal shunt tube prior to PEG insertion. We present the case of a 4-month-old male infant with shunted hydrocephalus who experienced shunt malfunction due to perforation of the distal shunt tubing after PEG placement.
WIVERN Illingworth, A. J.; Battaglia, A.; Bradford, J. ...
Bulletin of the American Meteorological Society,
08/2018, Letnik:
99, Številka:
8
Journal Article
Recenzirano
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This paper presents a conically scanning spaceborne Dopplerized 94-GHz radar Earth science mission concept: Wind Velocity Radar Nephoscope (WIVERN). WIVERN aims to provide global measurements of ...in-cloud winds using the Doppler-shifted radar returns from hydrometeors. The conically scanning radar could provide wind data with daily revisits poleward of 50°, 50-km horizontal resolution, and approximately 1-km vertical resolution. The measured winds, when assimilated into weather forecasts and provided they are representative of the larger-scale mean flow, should lead to further improvements in the accuracy and effectiveness of forecasts of severe weather and better focusing of activities to limit damage and loss of life. It should also be possible to characterize the more variable winds associated with local convection. Polarization diversity would be used to enable high wind speeds to be unambiguously observed; analysis indicates that artifacts associated with polarization diversity are rare and can be identified. Winds should be measurable down to 1 km above the ocean surface and 2 km over land. The potential impact of the WIVERN winds on reducing forecast errors is estimated by comparison with the known positive impact of cloud motion and aircraft winds. The main thrust of WIVERN is observing in-cloud winds, but WIVERN should also provide global estimates of ice water content, cloud cover, and vertical distribution, continuing the data series started by CloudSat with the conical scan giving increased coverage. As with CloudSat, estimates of rainfall and snowfall rates should be possible. These nonwind products may also have a positive impact when assimilated into weather forecasts.
To assess the feasibility of helium-3 magnetic resonance (MR) imaging with a three-dimensional fast low-angle shot (FLASH) sequence, He-3 gas (volume, 300 mL; pressure, 3 x 10(5) Pa; polarized up to ...45% by means of optimal pumping) was inhaled by five healthy volunteers and five patients with pulmonary diseases. All breath-hold examinations (22-42 seconds) were completed successfully. Normal ventilation was depicted with homogeneous high signal intensity, lesions were depicted as causing defects, and obstructive lung disease was depicted with severely inhomogeneous signal intensity.
Perhaps more than any other "-omics" endeavor, the accuracy and level of detail obtained from mapping the major connection pathways in the living human brain with diffusion MRI depend on the ...capabilities of the imaging technology used. The current tools are remarkable; allowing the formation of an "image" of the water diffusion probability distribution in regions of complex crossing fibers at each of half a million voxels in the brain. Nonetheless our ability to map the connection pathways is limited by the image sensitivity and resolution, and also the contrast and resolution in encoding of the diffusion probability distribution. The goal of our Human Connectome Project (HCP) is to address these limiting factors by re-engineering the scanner from the ground up to optimize the high b-value, high angular resolution diffusion imaging needed for sensitive and accurate mapping of the brain's structural connections. Our efforts were directed based on the relative contributions of each scanner component. The gradient subsection was a major focus since gradient amplitude is central to determining the diffusion contrast, the amount of T2signal loss, and the blurring of the water PDF over the course of the diffusion time. By implementing a novel 4-port drive geometry and optimizing size and linearity for the brain, we demonstrate a whole-body sized scanner with Gmax=300mT/m on each axis capable of the sustained duty cycle needed for diffusion imaging. The system is capable of slewing the gradient at a rate of 200T/m/s as needed for the EPI image encoding. In order to enhance the efficiency of the diffusion sequence we implemented a FOV shifting approach to Simultaneous MultiSlice (SMS) EPI capable of unaliasing 3 slices excited simultaneously with a modest g-factor penalty allowing us to diffusion encode whole brain volumes with low TR and TE. Finally we combine the multi-slice approach with a compressive sampling reconstruction to sufficiently undersample q-space to achieve a DSI scan in less than 5min. To augment this accelerated imaging approach we developed a 64-channel, tight-fitting brain array coil and show its performance benefit compared to a commercial 32-channel coil at all locations in the brain for these accelerated acquisitions. The technical challenges of developing the over-all system are discussed as well as results from SNR comparisons, ODF metrics and fiber tracking comparisons. The ultra-high gradients yielded substantial and immediate gains in the sensitivity through reduction of TE and improved signal detection and increased efficiency of the DSI or HARDI acquisition, accuracy and resolution of diffusion tractography, as defined by identification of known structure and fiber crossing.
We investigate the ‘singular sources method’ (SSM) for the reconstruction of 3D scattering obstacles with sound-soft, sound-hard or impedance boundary condition. The task of this work is the proof of ...concept for the ‘numerical feasibility’ of the SSM for reconstructions of 3D objects in acoustics. To our knowledge, these are the first numerical results for the SSM in three dimensions. In particular, we will show reconstructions for different geometric objects for which the boundary condition is not needed to be known in the reconstruction scheme.
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