Size and surface effects on the MRI relaxivity of manganese ferrite nanoparticle contrast agents

Superparamagnetic MnFe2O4 nanocrystals of different sizes were synthesized in high-boiling ether solvent and transferred into water using three different approaches. First, we applied a ligand exchange in order to form a water soluble polymer shell. Second, the particles were embedded into an amphiphilic polymer shell. Third, the nanoparticles were embedded into large micelles formed by lipids. Although all approaches lead to effective negative contrast enhancement, we observed significant differences concerning the magnitude of this effect. The transverse relaxivity, in particular r2*, is greatly higher for the micellar system compared to the polymer-coated particles using same-sized nanoparticles. We also observed an increase in transverse relaxivities with increasing particle size for the polymer-coated nanocrystals. The results are qualitatively compared with theoretical models describing the dependence of relaxivity on the size of magnetic spheres.     

Rotationskapazität nachgiebiger Stahlknoten

Rotation capacity of semi‐rigid steel joints. For plastic design of steel buildings containing semi‐rigid joints a design concept is presented. The check of sufficient rotation capacity of the joints is included in the design procedure. Experimental and analytical investigations were carried out to verify the determination of the joints' available rotation capacity. These investigations which are based on the concept of the macromechanical component model are summarized briefly. Conclusions have been drawn from a parameter study to set up an equation for the available rotation capacity of semi‐rigid steel joints. The integration of this equation into the beam line theory of an isolated girder enables establishing a design procedure for the check of sufficient rotation capacity of semi‐rigid steel joints.     

Electrochemical water disinfection. Part II: Hypochlorite production from potable water, chlorine consumption and the problem of calcareous deposits

The electrolytic production of hypochlorite from tap water in a flow-through reactor system is investigated using stacked platinum or iridium oxide coated titanium sheet or expanded metal electrodes. The influence of fast chlorine consumption and polarity reversal on the hypochlorite production rate was determined along with the dependence of the hypochlorite production rate on temperature, flow through velocity and current density. It was found that in most cases, the hypochlorite production rate was higher on iridium oxide compared to platinum electrodes. An increase in the flow-through velocity leads to an increased hypochlorite production rate while the hypochlorite production rate falls with increasing temperature.     

High Mobility Group Box 1 Protein in Cerebral Thromboemboli

High-mobility group box 1 protein (HMGB1) is a damage-associated molecular pattern (DAMP) involved in neutrophil extracellular trap (NET) formation and thrombosis. NETs are regularly found in cerebral thromboemboli. We here analyzed associated HMGB1 expression in human thromboemboli retrieved via mechanical thrombectomy from 37 stroke patients with large vessel occlusion. HMGB1 was detected in all thromboemboli, accounting for 1.7% (IQR 0.6–6.2%) of the total thromboemboli area and was found to be colocalized with neutrophils and NETs and in spatial proximity to platelets. Correlation analysis revealed that the detection of HMGB1 was strongly related to the number of neutrophils (r = 0.58, p = 0.0002) and platelets (r = 0.51, p = 0.001). Our results demonstrate that HMGB1 is a substantial constituent of thromboemboli causing large vessel occlusion stroke.     

Implications of climate-smart strategy adoption by farm households for food security in Tanzania

As the climate changes, farmers in developing countries seek to employ strategies to help them sustain food production. The objectives of this paper were to identify adaptation strategies in response to climate change and the determinants for their adoption, and to explore the impact of these strategies on food security. The analysis was based on a survey of 900 small-scale farmers in a semi-arid (Dodoma) and a semi-humid (Morogoro) region in Tanzania. Farmers in the semi-humid region tended to diversify their crops, i.e. added additional crop types. Given the more challenging environment in the semi-arid region, farmers there changed their portfolio of crops, i.e. substituted some crops or cultivars with others. Logistic regressions highlighted higher tolerance to risk, land ownership, education and experiences of farmers as drivers of adoption, while income diversification had a negative effect. The propensity score matching approach showed that adopters of climate-smart strategies are on-average more food-secure. These users showed a more diverse pattern of food consumption, greater protein intake and better economic access to food. Changing crop portfolios can help households to cope with climate-related shocks such as droughts and thus appears to be the best performing strategy, especially in terms of more stable food provisioning throughout the year.     

Optical coatings：trends and challenges

1Introduction Today,opticalcoatinghasbeenregardedas oneofthemostimportantsegmentinoptics technology[1].Itcansufficientlyimprovethe performanceofthewholeopticalsystem,satisfy thefunctionrequirements,andthereforeisan intensivelyactiveresearchfieldworldwide.Opticalcoatingscanbefoundinnearly everytechnicalapplicationstartingwithtelecom munications,spacetechnologies,andlasers.Meanwhile,itplaysasignificantroleinmany fieldsdevelopment,suchasphysics,chemistry andsynchrotronemissionapplication.Theeffi…     

Zero-phonon linewidth in CdSe/ZnS core/shell nanorods

High-resolution spectral hole-burning studies of CdSe/ZnS core/shell nanorods reveal a sharp zero-phonon line, with a line width dependent on the measurement time scale. The zero-phonon line width is attributed to contributions from radiative decay, spectral diffusion induced by surface electric field fluctuations, and phonon-assisted migration of excitons localized in the nanorods. A decoherence rate as small as 4.5 GHz has been observed, when the effects of spectral diffusion are suppressed in the spectral hole-burning measurement. Comparison between zero-phonon line widths in nanorods and spherical nanocrystals also elucidates important differences in the decoherence process between the one- and zero-dimensional nanostructures.     

Directed evolution of an esterase from Pseudomonas fluorescens yields a mutant with excellent enantioselectivity and activity for the kinetic resolution of a chiral building block

A triple mutant of an esterase from Pseudomonas fluorescens (PFE) that was created by directed evolution exhibited high enantioselectivity (E=89) in a kinetic resolution and yielded the building block (S)-but-3-yn-2-ol. Surprisingly, a mutation close to the active site caused the formation of inclusion bodies, but remote mutations were found to be responsible for the high selectivity. Back mutations gave a variant (double mutant PFE Ile76Val/Val175Ala) that showed excellent selectivity (E=96) and activity (20 min for 50% conversion, which corresponds to 1.25 U per mg of protein).