Implementation and evaluation of permeability-porosity and tortuosity-porosity relationships linked to mineral dissolution-precipitation

Changes of porosity, permeability, and tortuosity due to physical and geochemical processes are of vital importance for a variety of hydrogeological systems, including passive treatment facilities for contaminated groundwater, engineered barrier systems (EBS), and host rocks for high-level nuclear waste (HLW) repositories. Due to the nonlinear nature and chemical complexity of the problem, in most cases, it is impossible to verify reactive transport codes analytically, and code intercomparisons are the most suitable method to assess code capabilities and model performance. This paper summarizes model intercomparisons for six hypothetical scenarios with generally increasing geochemical or physical complexity using the reactive transport codes CrunchFlow, HP1, MIN3P, PFlotran, and TOUGHREACT. Benchmark problems include the enhancement of porosity and permeability through mineral dissolution, as well as near complete clogging due to localized mineral precipitation, leading to reduction of permeability and tortuosity. Processes considered in the benchmark simulations are advective-dispersive transport in saturated media, kinetically controlled mineral dissolution-precipitation, and aqueous complexation. Porosity changes are induced by mineral dissolution-precipitation reactions, and the Carman-Kozeny relationship is used to describe changes in permeability as a function of porosity. Archie’s law is used to update the tortuosity and the pore diffusion coefficient as a function of porosity. Results demonstrate that, generally, good agreement is reached amongst the computer models despite significant differences in model formulations. Some differences are observed, in particular for the more complex scenarios involving clogging; however, these differences do not affect the interpretation of system behavior and evolution.

Hydrogel intraocular lens exchange: five-year experience

BACKGROUND: This study presents an evaluation of the preoperative and postoperative best corrected visual acuity (BCVA), as well as of the incidence of perioperative and postoperative complications after opacified hydrogel intraocular lens (IOL) exchange. PATIENTS AND METHODS: We exchanged opacified hydrogel IOLs (Hydroview H 60 M, Bausch ; Lomb) in 55 patients (55 eyes). Preoperative and postoperative BCVA were compared. Intraoperative and postoperative complications were recorded. Follow-up period ranged from 3 months to 24 months. RESULTS: Mean BCVA improved significantly from 0.05 preoperatively to 0.4 at 3 months postoperatively and to 0.2 at the end of the follow-up period. Forty patients (72.7 %) reported visual improvement. The procedure was uneventful in 30 eyes (54.5 %) with complete removal of the opacified IOL optics and haptics. Intraoperative complications included partial zonular dehiscence in 10 eyes (18.2 %), en block capsular bag-IOL extraction in 2 eyes (3.6 %), posterior capsule rupture in 2 eyes (3.6 %), hyphema in 3 eyes (5.5 %), retained haptics in 8 eyes (14.5 %). Postoperative complications included corneal decompensation in 5 eyes (9.1 %), cystoid macular edema in 15 eyes (27.3 %), elevated intraocular pressure in 6 eyes (10.9 %), and retinal detachment in 1 eye (1.8 %). CONCLUSIONS: Visual acuity improved after opacified hydrogel IOL exchange, however, coexistent ocular morbidity as well as the appearance of serious postoperative complications may not yield the expected results. For these reasons extensive informed consent is mandatory.

Clutter elimination for deep clinical optoacoustic imaging using localised vibration tagging (LOVIT)

This paper investigates a novel method which allows clutter elimination in deep optoacoustic imaging. Clutter significantly limits imaging depth in clinical optoacoustic imaging, when irradiation optics and ultrasound detector are integrated in a handheld probe for flexible imaging of the human body. Strong optoacoustic transients generated at the irradiation site obscure weak signals from deep inside the tissue, either directly by propagating towards the probe, or via acoustic scattering. In this study we demonstrate that signals of interest can be distinguished from clutter by tagging them at the place of origin with localised tissue vibration induced by the acoustic radiation force in a focused ultrasonic beam. We show phantom results where this technique allowed almost full clutter elimination and thus strongly improved contrast for deep imaging. Localised vibration tagging by means of acoustic radiation force is especially promising for integration into ultrasound systems that already have implemented radiation force elastography.

ATMOSPHERIC RETRIEVAL ANALYSIS OF THE DIRECTLY IMAGED EXOPLANET HR 8799b

Directly imaged exoplanets are unexplored laboratories for the application of the spectral and temperature retrieval method, where the chemistry and composition of their atmospheres are inferred from inverse modeling of the available data. As a pilot study, we focus on the extrasolar gas giant HR 8799b, for which more than 50 data points are available. We upgrade our non-linear optimal estimation retrieval method to include a phenomenological model of clouds that requires the cloud optical depth and monodisperse particle size to be specified. Previous studies have focused on forward models with assumed values of the exoplanetary properties; there is no consensus on the best-fit values of the radius, mass, surface gravity, and effective temperature of HR 8799b. We show that cloud-free models produce reasonable fits to the data if the atmosphere is of super-solar metallicity and non-solar elemental abundances. Intermediate cloudy models with moderate values of the cloud optical depth and micron-sized particles provide an equally reasonable fit to the data and require a lower mean molecular weight. We report our best-fit values for the radius, mass, surface gravity, and effective temperature of HR 8799b. The mean molecular weight is about 3.8, while the carbon-to-oxygen ratio is about unity due to the prevalence of carbon monoxide. Our study emphasizes the need for robust claims about the nature of an exoplanetary atmosphere to be based on analyses involving both photometry and spectroscopy and inferred from beyond a few photometric data points, such as are typically reported for hot Jupiters.

Highly efficient ketone body treatment in multiple acyl-CoA dehydrogenase deficiency-related leukodystrophy.

BACKGROUND Multiple acyl-CoA dehydrogenase deficiency- (MADD-), also called glutaric aciduria type 2, associated leukodystrophy may be severe and progressive despite conventional treatment with protein- and fat-restricted diet, carnitine, riboflavin, and coenzyme Q10. Administration of ketone bodies was described as a promising adjunct, but has only been documented once. METHODS We describe a Portuguese boy of consanguineous parents who developed progressive muscle weakness at 2.5 y of age, followed by severe metabolic decompensation with hypoglycaemia and coma triggered by a viral infection. Magnetic resonance (MR) imaging showed diffuse leukodystrophy. MADD was diagnosed by biochemical and molecular analyses. Clinical deterioration continued despite conventional treatment. Enteral sodium D,L-3-hydroxybutyrate (NaHB) was progressively introduced and maintained at 600 mg/kg BW/d (≈3% caloric need). Follow up was 3 y and included regular clinical examinations, biochemical studies, and imaging. RESULTS During follow up, the initial GMFC-MLD (motor function classification system, 0 = normal, 6 = maximum impairment) level of 5-6 gradually improved to 1 after 5 mo. Social functioning and quality of life recovered remarkably. We found considerable improvement of MR imaging and spectroscopy during follow up, with a certain lag behind clinical recovery. There was some persistent residual developmental delay. CONCLUSION NaHB is a highly effective and safe treatment that needs further controlled studies.

Optical Tolerance Analysis of the Multi-Beam Limb Viewing Instrument STEAMR

In this paper, we report on an optical tolerance analysis of the submillimeter atmospheric multi-beam limb sounder, STEAMR. Physical optics and ray-tracing methods were used to quantify and separate errors in beam pointing and distortion due to reflector misalignment and primary reflector surface deformations. Simulations were performed concurrently with the manufacturing of a multi-beam demonstrator of the relay optical system which shapes and images the beams to their corresponding receiver feed horns. Results from Monte Carlo simulations show that the inserts used for reflector mounting should be positioned with an overall accuracy better than 100 μm (~ 1/10 wavelength). Analyses of primary reflector surface deformations show that a deviation of magnitude 100 μm can be tolerable before deployment, whereas the corresponding variations should be less than 30 μm during operation. The most sensitive optical elements in terms of misalignments are found near the focal plane. This localized sensitivity is attributed to the off-axis nature of the beams at this location. Post-assembly mechanical measurements of the reflectors in the demonstrator show that alignment better than 50 μm could be obtained.

Bathymetry of Lake Constance - State-of-the-art in surveying a large lake

In 2014 the by far largest German lake has been newly surveyed. The transnational project is funded by the European Union and delivers a detailed 3D-model of the lake- floor. The German project name is »Tiefenschärfe – Hochauflösende Vermessung Bo- densee«, which in English roughly means: high-resolution survey of Lake Constance. The German term »Tiefenschärfe« (in optics and photography: depth of field) plays with the meanings of »Tiefe« (depth) and »Schärfe« (sharpness). The result of the sur- vey shall be a clear and sharp image of the deep and shallow lake- floor. At present the LiDAR and multibeam data are still processed, but first results are presented in this article.

Assessing the impact of multiple stressors on aquatic biota: the receptor's side matters.

Aquatic ecosystems are confronted with multiple stress factors. Current approaches to assess the risk of anthropogenic stressors to aquatic ecosystems are developed for single stressors and determine stressor effects primarily as a function of stressor properties. The cumulative impact of several stressors, however, may differ markedly from the impact of the single stressors and can result in nonlinear effects and ecological surprises. To meet the challenge of diagnosing and predicting multiple stressor impacts, assessment strategies should focus on properties of the biological receptors rather than on stressor properties. This change of paradigm is required because (i) multiple stressors affect multiple biological targets at multiple organizational levels, (ii) biological receptors differ in their sensitivities, vulnerabilities, and response dynamics to the individual stressors, and (iii) biological receptors function as networks, so that actions of stressors at disparate sites within the network can lead via indirect or cascading effects, to unexpected outcomes.

An adaptive Newton-method based on a dynamical systems approach

The traditional Newton method for solving nonlinear operator equations in Banach spaces is discussed within the context of the continuous Newton method. This setting makes it possible to interpret the Newton method as a discrete dynamical system and thereby to cast it in the framework of an adaptive step size control procedure. In so doing, our goal is to reduce the chaotic behavior of the original method without losing its quadratic convergence property close to the roots. The performance of the modified scheme is illustrated with various examples from algebraic and differential equations.