Atrophy of basal forebrain and abnormal Functional Connectivity of the basal forebrain in Subjective Cognitive Decline

Subjective Cognitive Decline (SCD) is increasingly recognized as an efficient concept to study in an early preclinical stage of Alzheimer’s disease (AD). It is marked by a perceived subjective worsening of cognitive function compared to the earlier performance level without noticeable impairments in standard neuro-psychological testing. Even though SCD individuals do not necessarily share the same underlying AD pathology, a variety of studies have identified an increased AD biomarker positivity and risk to develop clinical AD. SCD also show atrophy in regions that are known to be vulnerable to AD-pathology (i.e. hippocampus, entorhinal cortex, precuneus). Recent studies suggest that cholinergic basal forebrain (BF) volume loss even precedes degeneration of the entorhinal cortex. This thesis focusses on the question how BF-atrophy relates to amyloid pathology in SCD and healthy controls and tried to further investigate the functional consequences as assessable by resting state functional MRI. The three conducted studies are based on German Center for Neurodegenerative Diseases Longitudinal Cognitive Impairment and Dementia Study (DELCODE) project. Study 1 examined cholinergic BF volume alterations in SCD. A significant interaction between diagnosis (SCD vs. Healthy control [HC]) and CSF amyloid status was found, with posterior of NBM volume reductions only in amyloid-positive SCD. The observed volume reduction of the cholinergic BF in amyloid-positive SCD and the absence of any volume reductions in the amyloid-positive HC suggests that SCD plus amyloid pathology reflects an advanced stage of preclinical AD, revealing the beginning neurodegeneration on a macroscopic level. The second study revealed that the degeneration of the BF alters the functional connectivity to certain cortical brain regions. More or less the overall trend observed was a reduced connectivity. Based on a group stratification with respect to cortical amyloid deposition, the alteration of the functional connectivity of the precuneus was investigated in Study 3. Compared to amyloid-negative SCD, significantly higher regional homogeneity within the precuneus was found for amyloid-positive SCD as well as a higher FC to occipital areas. Taking everything together, the presented data indicate that the cholinergic system, especially the posterior part of the NBM (Ch4p) seems to play a key role in the very early stage of AD. It affects not only memory processes but has also a ‘long range effect’ leading to decreased FC. SCD appears to be a hallmark on the AD-trajectory marking the point when neurodegenerative process begins to exceed a level that can’t be functionally compensated, and therefore amyloid-positive SCD might reflect the progression from an asymptomatic stage (stage 1) to stage 2 of the Alzheimer’s continuum, where cognitive functions start to impairment

Symmetry selective third harmonic generation from plasmonic metacrystals

Nonlinear processes are often governed by selection rules imposed by the symmetries of the molecular configurations. The most well-known examples include the role of mirror symmetry breaking for the generation of even harmonics, and the selection rule related to the rotation symmetry in harmonic generation for fundamental beams with circular polarizations. While the role of mirror symmetry breaking in second harmonic generation has been extensively studied in plasmonic systems, the investigation on selection rules pertaining to circular polarization states of harmonic generation has been limited to crystals, i.e. symmetries at the atomic level. Here we demonstrate the rotational symmetry dependent third harmonic generation from nonlinear plasmonic metacrystals. We show that the selection rule can be imposed by the rotational symmetry of meta-crystals embedded into an isotropic organic nonlinear thin film. The results presented here may open new avenues for designing symmetry-dependent nonlinear optical responses with tailored plasmonic nanostructures.Comment: 13 pages, 3 figure

Effect of cooling pad installation on indoor airflow distribution in a tunnel-ventilated laying-hen house

Extra cooling pads on the sidewalls are needed for larger poultry houses using tunnel ventilation system. Preliminary study showed that the airflow velocity going through different aisles varies greatly when the extra pads are installed at the end of sidewalls, making a “[”-shape air inlet. Combined with field tests, the CFD (computational fluid dynamics) technology was used to study the uniformity of airflow distribution in a tunnel-ventilated laying-hen house. The air distribution was first monitored in a layer house to find the main reason resulting in the variations of airflows in different aisles. Then CFD simulations were carried out with different distances (D=2 m, 3 m or 4 m) between the pads on end-wall and the extra pads on side walls. The field test showed that airflow streams from the different groups of cooling pads collided vertically at the house corners, mixed with each other, then flew towards the center of the house. This was the main reason that the wind speed in the middle aisle was much higher than in other aisles, leaving large zones of lower ventilation in the aisles adjacent to the sidewalls. The results of CFD simulations indicated that air distributions could be significantly improved when the extra pieces of pads were moved away for an appropriate distance from the end cooling pads. As far as conventional poultry house with a span of 12 m, the air speeds in different aisles were more uniform when this distance was about 3 m

Experimental Study on the Adsorption of Heavy Metal Ions in Wastewater by Modified Bentonite

This is an article in the field of ceramics and composites. In order to study the adsorption effect of modified bentonite on heavy metal ions in sewage, the effects of pH value, initial concentration, time, solid-liquid ratio, temperature and particle size on the adsorption effect of bentonite were analyzed. And microscopic means were used to study the changes of the internal mineral composition of the bentonite before and after the adsorption of heavy metal ions and the change law of the infrared spectra. The results showed that when the modified bentonite content was 0.2 g, the adsorption time was 1.5 h, the temperature was set to 40 ℃, the pH value was set to 6, the initial concentration was set to 200 mg/L and the solid-to-liquid ratio was set to 0.8 g/L, the adsorption effect was the best. After the modified bentonite had undergone an adsorption test, an obvious CuSO4 diffraction peak could be detected. However, other mineral components inside the modified bentonite remained unchanged, which also showed that the modified bentonite could effectively adsorb copper ions in sewage