Combined Shape and Parameter Identification Applied to a Porous Media Simulation

For material parameter estimation as well as shape identification a variety of research and commercial software exists. These tools are often integrated directly into an FEM program or use the FEM solver as a subroutine. However, the two problems are always considered as separate tasks which are solved by separate software packages. When simulating structured specimens, the considered domain often consists of different material types. These are modeled using different material domains. Frequently, the material parameters and the shape of the material domains are unknown. As both components considerably influence the simulation results, separate identification yields poor results. The inhouse identification and optimization software SPC-Opt developed at the department of Solid Mechanics at Chemnitz University of Technology is capable of solving shape and parameter identification simultaneously. Here, the key concept is an abstract formulation of parameters as variables that influence FEM computations. In this paper, the general design and algorithms are presented. Moreover, the application is demonstrated on an academic example using a simple porous media constitutive model

Isotopically Light Cd in Sediments Underlying Oxygen Deficient Zones

Cadmium is a trace metal of interest in the ocean partly because its concentration mimics that of phosphate. However, deviations from the global mean dissolved Cd/PO4 relationship are present in oxygen deficient zones, where Cd is depleted relative to phosphate. This decoupling has been suggested to result from cadmium sulphide (CdS) precipitation in reducing microenvironments within sinking organic matter. We present Cd concentrations and Cd isotope compositions in organic-rich sediments deposited at several upwelling sites along the northeast Pacific continental margin. These sediments all have enriched Cd concentrations relative to crustal material. We calculate a net accumulation rate of Cd in margin settings of between 2.6 to 12.0 × 107 mol/yr, higher than previous estimates, but at the low end of a recently published estimate for the magnitude of the marine sink due to water column CdS precipitation. Cadmium in organic-rich sediments is isotopically light (δ114/110CdNIST-3108 = +0.02 ± 0.14‰, n = 26; 2 SD) compared to deep seawater (+0.3 ± 0.1‰). However, isotope fractionation during diagenesis in continental margin settings appears to be small. Therefore, the light Cd isotope composition of organic-rich sediments is likely to reflect an isotopically light source of Cd. Non-quantitative biological uptake of light Cd by phytoplankton is one possible means of supplying light Cd to the sediment, which would imply that Cd isotopes could be used as a tracer of past ocean productivity. However, water column CdS precipitation is also predicted to preferentially sequester light Cd isotopes from the water column, which could obfuscate Cd as a tracer. We also observe notably light Cd isotope compositions associated with elevated solid phase Fe concentrations, suggesting that scavenging of Cd by Fe oxide phases may contribute to the light Cd isotope composition of sediments. These multiple possible sources of isotopically light Cd to sediments, along with evidence for complex particle cycling of Cd in the water column, bring into question the straightforward application of Cd isotopes as a paleoproductivity proxy

A geochemical study of the winonaites: Evidence for limited partial melting and constraints on the precursor composition

The winonaites are primitive achondrites which are associated with the IAB iron meteorites. Textural evidence implies heating to at least the Fe, Ni–FeS cotectic, but previous geochemical studies are ambiguous about the extent of silicate melting in these samples. Oxygen isotope evidence indicates that the precursor material may be related to the carbonaceous chondrites. Here we analysed a suite of winonaites for modal mineralogy and bulk major- and trace-element chemistry in order to assess the extent of thermal processing as well as constrain the precursor composition of the winonaite-IAB parent asteroid. Modal mineralogy and geochemical data are presented for eight winonaites. Textural analysis reveals that, for our sub-set of samples, all except the most primitive winonaite (Northwest Africa 1463) reached the Fe, Ni–FeS cotectic. However, only one (Tierra Blanca) shows geochemical evidence for silicate melting processes. Tierra Blanca is interpreted as a residue of small-degree silicate melting. Our sample of Winona shows geochemical evidence for extensive terrestrial weathering. All other winonaites studied here (Fortuna, Queen Alexander Range 94535, Hammadah al Hamra 193, Pontlyfni and NWA 1463) have chondritic major-element ratios and flat CI-normalised bulk rare-earth element patterns, suggesting that most of the winonaites did not reach the silicate melting temperature. The majority of winonaites were therefore heated to a narrow temperature range of between ∼1220 (the Fe, Ni–FeS cotectic temperature) and ∼1370 K (the basaltic partial melting temperature). Silicate inclusions in the IAB irons demonstrate partial melting did occur in some parts of the parent body (Ruzicka and Hutson, 2010), thereby implying heterogeneous heat distribution within this asteroid. Together, this indicates that melting was the result of internal heating by short-lived radionuclides. The brecciated nature of the winonaites suggests that the parent body was later disrupted by a catastrophic impact, which allowed the preservation of the largely unmelted winonaites. Despite major-element similarities to both ordinary and enstatite chondrites, trace-element analysis suggests the winonaite parent body had a carbonaceous chondrite-like precursor composition. The parent body of the winonaites was volatile-depleted relative to CI, but enriched compared to the other carbonaceous classes. The closest match are the CM chondrites; however, the specific precursor is not sampled in current meteorite collections

Isotopically Light Cd in Sediments Underlying Oxygen Deficient Zones

Cadmium is a trace metal of interest in the ocean partly because its concentration mimics that of phosphate. However, deviations from the global mean dissolved Cd/PO4 relationship are present in oxygen deficient zones, where Cd is depleted relative to phosphate. This decoupling has been suggested to result from cadmium sulphide (CdS) precipitation in reducing microenvironments within sinking organic matter. We present Cd concentrations and Cd isotope compositions in organic-rich sediments deposited at several upwelling sites along the northeast Pacific continental margin. These sediments all have enriched Cd concentrations relative to crustal material. We calculate a net accumulation rate of Cd in margin settings of between 2.6 to 12.0 × 107 mol/yr, higher than previous estimates, but at the low end of a recently published estimate for the magnitude of the marine sink due to water column CdS precipitation. Cadmium in organic-rich sediments is isotopically light (δ114/110CdNIST-3108 = +0.02 ± 0.14‰, n = 26; 2 SD) compared to deep seawater (+0.3 ± 0.1‰). However, isotope fractionation during diagenesis in continental margin settings appears to be small. Therefore, the light Cd isotope composition of organic-rich sediments is likely to reflect an isotopically light source of Cd. Non-quantitative biological uptake of light Cd by phytoplankton is one possible means of supplying light Cd to the sediment, which would imply that Cd isotopes could be used as a tracer of past ocean productivity. However, water column CdS precipitation is also predicted to preferentially sequester light Cd isotopes from the water column, which could obfuscate Cd as a tracer. We also observe notably light Cd isotope compositions associated with elevated solid phase Fe concentrations, suggesting that scavenging of Cd by Fe oxide phases may contribute to the light Cd isotope composition of sediments. These multiple possible sources of isotopically light Cd to sediments, along with evidence for complex particle cycling of Cd in the water column, bring into question the straightforward application of Cd isotopes as a paleoproductivity proxy

Factors influencing visual acuity after intravitreal triamcinolone acetonide as treatment of exudative age related macular degeneration

Aim: To evaluate factors influencing change in visual acuity (VA) after intravitreal injection of triamcinolone acetonide as treatment of exudative age related macular degeneration (AMD). Methods: This prospective, interventional, comparative non-randomised clinical case series study included 94 patients (99 eyes) showing progressive exudative AMD with occult (n = 61 eyes), minimally classic (n = 18), predominantly classic (n = 1), or totally classic (n = 8) subfoveal neovascularisation. Mean follow up was 8.5 (SD 4.7) months (median, 7.3 months; range 3.1–24.5 months). All patients received an intravitreal injection of 20–25 mg of triamcinolone acetonide. Results: An increase in best VA of at least one line on the Snellen charts was found in 63 (63.1%) eyes. Correspondingly, mean VA increased significantly (p<0.001) from 0.17 (SD 0.13) to 0.22 (SD 0.17) after the injection. Postoperative increase in VA was significantly (p<0.001) and negatively correlated with preoperative VA (correlation coefficient, −0.49). Gain in visual acuity was significantly (p = 0.009) higher if preoperative visual acuity was less than 0.08 (gain: 3.2 (SD 2.9) Snellen lines) than if preoperative VA ranged between 0.08 and 0.20 (gain: 1.2 (SD 2.2) Snellen lines). Change in VA was significantly (p = 0.016) less if preoperative VA was higher than 0.20 (change: −0.8 (SD 3.4) Snellen lines). Maximal gain in VA was significantly (p = 0.035) larger in eyes with retinal pigment epithelium detachment than in eyes with minimally classic subfoveal neovascularisation. This was statistically independent of age (p = 0.99), refractive error (p = 0.88), sex (p = 0.92), and duration of follow up (p = 0.46). Conclusions: Gain in VA after intravitreal injection of 20–25 mg of triamcinolone acetonide is significantly and negatively correlated with preoperative VA. It is significantly larger in eyes with retinal pigment epithelium detachment than in eyes with minimally classic subfoveal neovascularisation

Diffuse diabetic macular oedema treated by intravitreal triamcinolone acetonide: a comparative, non-randomised study

Aim: To report on visual outcome of patients receiving an intravitreal injection of triamcinolone acetonide for treatment of diffuse diabetic macular oedema. Methods: Prospective, comparative, non-randomised clinical interventional study included 136 patients with diffuse diabetic macular oedema. Patients of the study group (97 eyes) received an intravitreal injection of 20–25 mg of triamcinolone acetonide and no other retinal treatment. Patients of the control group (69 eyes) received focal or panretinal laser treatment if indicated. Mean (standard deviation) follow up was 8.4 (SD 6.0) months (range 1.03–25.2 months). Results: Visual acuity (VA) increased significantly (p<0.001) in the study group with 66 (68%) eyes gaining in VA by at least two Snellen lines. In the control group, VA did not change significantly during the first 4 months of follow up, and decreased significantly (p<0.001) towards the end of the follow up. Difference in change of best VA was significant (p<0.001) between both groups. Correspondingly, the number of patients with VA improvement of two or more Snellen lines and visual loss of two or more Snellen lines, respectively, was significantly (p<0.001) higher and lower, respectively, in the study group. Conclusions: Intravitreal triamcinolone acetonide can temporarily increase VA in some patients with diffuse diabetic macular oedema