Exploring the oxidation behavior of undiluted and diluted iron particles for energy storage: Mössbauer spectroscopic analysis and kinetic modeling.

Iron is an abundant and non-toxic element that holds great potential as energy carrier for large-scale and long-term energy storage. While from a general viewpoint iron oxidation is well-known, the detailed kinetics of oxidation for micrometer sized particles are missing, but required to enable large-scale utilization for energy production. In this work, iron particles are subjected to temperature-programmed oxidation. By dilution with boron nitride a sintering of the particles is prevented enabling to follow single particle effects. The mass fractions of iron and its oxides are determined for different oxidation times using Mössbauer spectroscopy. On the basis of the extracted phase compositions obtained at different times and temperatures (600-700 °C), it can be concluded that also for particles the oxidation follows a parabolic rate law. The parabolic rate constants are determined in this transition region. Knowledge of the particle size distribution and its consideration in modeling the oxidation kinetics of iron powder has proven to be crucial.

Can Small Polyaromatics Describe Their Larger Counterparts for Local Reactions? A Computational Study on the H-Abstraction Reaction by an H-Atom from Polyaromatics.

Hydrogen abstraction is one of the crucial initial key steps in the combustion of polycyclic aromatic hydrocarbons. For an accurate theoretical prediction of heterogeneous combustion processes, larger systems need to be treated as compared to pure gas phase reactions. We address here the question on how transferable activation and reaction energies computed for small molecular models are to larger polyaromatics. The approximate transferability of energy contributions is a key assumption for multiscale modeling approaches. To identify efficient levels of accuracy, we start with accurate coupled-cluster and density functional theory (DFT) calculations for different sizes of polyaromatics. More approximate methods as the reactive force-field ReaxFF and the extended semi-empirical tight binding (xTB) methods are then benchmarked against these data sets in terms of reaction energies and equilibrium geometries. Furthermore, we analyze the role of bond-breaking and relaxation energies, vibrational contributions, and post-Hartree-Fock correlation corrections on the reaction, and for the activation energies, we analyze the validity of the Bell-Evans-Polanyi and Hammond principles. First, we find good transferability for this process and that the predictivity of small models at high theoretical levels is way superior than any approximate method can deliver. Second, ReaxFF can serve as a qualitative exploration method, whereas GFN2-xTB in combination with GFN1-xTB appears as a favorable tool to bridge between DFT and ReaxFF so that we propose a multimethod scheme with employing ReaxFF, GFN1/GFN2-xTB, DFT, and coupled cluster to cope effectively with such a complex reactive system.

FGFR-ERK signaling is an essential component of tissue separation.

Formation of a constriction and tissue separation between parent and young polyp is a hallmark of the Hydra budding process and controlled by fibroblast growth factor receptor (FGFR) signaling. Appearance of a cluster of cells positive for double phosphorylated ERK (dpERK) at the late separation site indicated that the RAS/MEK/ERK pathway might be a downstream target of the Hydra Kringelchen FGFR. In fact, inhibition of ERK phosphorylation by the MEK inhibitor U0126 reversibly delayed bud detachment and prevented formation of the dpERK-positive cell cluster indicating de novo-phosphorylation of ERK at the late bud base. In functional studies, a dominant-negative Kringelchen FGFR prevented bud detachment as well as appearance of the dpERK-positive cell cluster. Ectopic expression of full length Kringelchen, on the other hand, induced a localized rearrangement of the actin cytoskeleton at sites of constriction, localized ERK-phosphorylation and autotomy of the body column. Our data suggest a model in which (i) the Hydra FGFR targets, via an unknown pathway, the actin cytoskeleton to induce a constriction and (ii) FGFR activates MEK/ERK signaling at the late separation site to allow tissue separation.

Three consecutive generations of nephridia occur during development of Platynereis dumerilii (Annelida, Polychaeta).

Molecular data for nephridial development in polychaetes are not available yet. The scope of our work was to establish a reference system for future investigations using two markers for nephridial development: beta-tubulin as marker for cilia and alkaline phosphatase (AP) activity for secretory epithelia. The markers identified, unexpectedly, three consecutively forming generations of nephridia: (1) a transitory unciliated, but AP-positive head kidney, (2) a transitory larval nephridium, which undergoes a morphological transition from a protonephridium to a funnelled nephridium concomitant with the development of the coelomic cavity and finally, (3) the serially arranged metanephridia. The spatial arrangement of larval and definitive nephridia, revealed an up to now unknown developmental boundary between the synchronously forming larval and the serially proliferating definitive segments. Development of three consecutive sets of nephridia with different morphology and biochemical properties was unexpected and reveals an interesting multistep process in the development of excretory structures in Platynereis.

Quality of life and patient satisfaction after reoperation for primary hyperparathyroidism: analysis of long-term results.

Morbidity after reoperation for persistent or recurrent primary hyperparathyroidism (pHPT) is higher than after primary surgery. According to our experience, there is a contrast between postoperative normalization of laboratory parameters and the quality of life/patient satisfaction after reoperation. Therefore the aim of the study was to analyze the outcomes of reoperations in comparison to primary surgery. We evaluated the patients' reported quality of life using the SF-36 (an accepted health status assessment tool) and complete prospectively documented perioperative and follow-up data including postoperative complications. Additionally, we searched for reasons why primary surgical intervention did not succeed. In a prospective cohort study the perioperative data of 653 consecutive patients with pHPT, including 75 reoperated patients (11.5%) who underwent parathyroidectomy between 1987 and 1999, were evaluated by uni- and multivariate analysis. At a median 78 months (6-156 months) postoperatively, all patients underwent a planned follow-up that included the SF-36, physical examination, and laboratory investigations. A total of 51 reoperated patients were available for follow-up. Postoperative alleviation of symptoms or being symptom-free was reported by 70.6%. Patients after reoperation had lower SF-36 scores in all health domains postoperatively than patients after a primary operation. Of the reoperated patients, 19.6% stated that after evaluating the development of their complaints they would not consent to reoperation again. Subgroup analysis showed that 80% of patients with postoperatively persistent pHPT, 60% of those who did not observe symptom alleviation, and 44% of those after sternotomy were in the group of dissatisfied patients. Surprisingly, none of the patients with more than one reoperation, only two of the five patients with permanent recurrent laryngeal nerve injury, and only one of the four patients with persistent hypoparathyroidism were dissatisfied overall. Parathyroidectomy resulted in normocalcemia in 90.2% of the reoperated patients, with an operative morbidity of 27.4% and no mortality. After an unsuccessful operation for pHPT, patients should be treated at an expert center to avoid persistent hypercalcemia. Reoperations necessitating sternotomy should be restricted to patients with severe symptoms and signs.