Increasing stimulus similarity drives nonmonotonic representational change in hippocampus

Studies of hippocampal learning have obtained seemingly contradictory results, with manipulations that increase coactivation of memories sometimes leading to differentiation of these memories, but sometimes not. These results could potentially be reconciled using the nonmonotonic plasticity hypothesis, which posits that representational change (memories moving apart or together) is a U-shaped function of the coactivation of these memories during learning. Testing this hypothesis requires manipulating coactivation over a wide enough range to reveal the full U-shape. To accomplish this, we used a novel neural network image synthesis procedure to create pairs of stimuli that varied parametrically in their similarity in high-level visual regions that provide input to the hippocampus. Sequences of these pairs were shown to human participants during high-resolution fMRI. As predicted, learning changed the representations of paired images in the dentate gyrus as a U-shaped function of image similarity, with neural differentiation occurring only for moderately similar images.

Engineering Commercial TiO2 Powder into Tailored Beads for Efficient Water Purification

In this study, efficient commercial photocatalyst (Degussa P25) nanoparticles were effectively dispersed and stabilized in alginate, a metal binding biopolymer. Taking advantage of alginate’s superior metal chelating properties, copper nanoparticle-decorated photocatalysts were developed after a pyrolytic or calcination-sintering procedure, yielding ceramic beads with enhanced photocatalytic and mechanical properties, excellent resistance to attrition, and optimized handling compared to powdered photocatalysts. The morphological and structural characteristics were studied using LN2 porosimetry, SEM, and XRD. The abatement of an organic pollutant (Methyl Orange, MO) was explored in the dark and under UV irradiation via batch experiments. The final properties of the photocatalytic beads were defined by both the synthesis procedure and the heat treatment conditions, allowing for their further optimization. It was found that the pyrolytic carbon residuals enabled the adhesion of the TiO2 nanoparticles, acting as binder, and increased the MO adsorption capacity, leading to increased local concentration in the photocatalyst vicinity. Well dispersed Cu nanoparticles were also found to enhance photocatalytic activity. The prepared photocatalysts exhibited increased MO adsorption capacity (up to 3.0 mg/g) and also high photocatalytic efficiency of about 50% MO removal from water solutions, reaching an overall MO rejection of about 80%, at short contact times (3 h). Finally, the prepared photocatalysts kept their efficiency for at least four successive photocatalytic cycles.

White light emission from lead-free mixed-cation doped Cs2SnCl6 nanocrystals

We have designed a synthesis procedure to obtain Cs2SnCl6 nanocrystals (NCs) doped with metal ion(s) to emit visible light.

Planar Compliance Realization with Two 3-Joint Serial Manipulators Connected in Parallel

In this paper, the realization of any specified planar compliance with two 3R serial elastic mechanisms is addressed. Using the concepts of dual elastic mechanisms, it is shown that the realization of a compliant behavior with 2 serial mechanisms connected in parallel is equivalent to its realization with a 6-spring fully parallel mechanism. Since the spring axes of a 6-spring parallel mechanism indicate the geometry of a dual 3R serial mechanism, a new synthesis procedure for the realization of a stiffness matrix with a 6-spring parallel mechanism is first developed. Then, this result is extended to a geometric construction-based synthesis procedure for two 3-joint serial mechanisms.

Defects-assisted piezoelectric response in liquid exfoliated MoS2 nanosheets

MoS2 is an intrinsic piezoelectric material which offers applications such as energy harvesting, sensors, actuators, flexible electronics, energy storage and more. Surprisingly, there are not any suitable, yet economical methods that can produce quality nanosheets of MoS2 in large quantities, hence limiting the possibility of commercialisation of its applications. Here, we demonstrate controlled synthesis of highly crystalline MoS2 nanosheets via liquid phase exfoliation of bulk MoS2, following which we report piezoelectric response from the exfoliated nanosheets. The method of piezo force microscopy (PFM) was employed to explore the piezo response in mono, bi, tri and multilayers of MoS2 nanosheets. The effective piezoelectric coefficient of MoS2 varies from 9.6 pm/V to 25.14 pm/V. We attribute piezoelectric response in MoS2 nanosheets to the defects formed in it during the synthesis procedure. The presence of defects is confirmed by X-ray photoelectron spectroscopy (XPS).

Comprehensive Overview on Zinc Oxide Nanostructures

Zinc oxide is technologically important and ZnO thin layers are widely used in sensors, transducers and catalysts designing. However, after the introduction of nanoscience and nanotechnology the gear has been shifted to its smaller counterpart in contrast to its bulk one. In this review typical synthesis procedure, growth process, classical property, and a few biological perspectives of zinc oxide nanostructures have been highlighted. In coming years new synthetic strategy, benign fabrication will be introduced with plethora of versatile and beneficial applications based on zinc oxide nanostructures.

CO2 Adsorption on Modified Mesoporous Silicas: The Role of the Adsorption Sites

The post-synthesis procedure for cyclic amine (morpholine and 1-methylpiperazine) modified mesoporous MCM-48 and SBA-15 silicas was developed. The procedure for preparation of the modified mesoporous materials does not affect the structural characteristics of the initial mesoporous silicas strongly. The initial and modified materials were characterized by XRD, N2 physisorption, thermal analysis, and solid-state NMR. The CO2 adsorption of the obtained materials was tested under dynamic and equilibrium conditions. The NMR data revealed the formation of different CO2 adsorbed forms. The materials exhibited high CO2 absorption capacity lying above the benchmark value of 2 mmol/g and stretching out to the outstanding 4.4 mmol/g in the case of 1-methylpiperazin modified MCM-48. The materials are reusable, and their CO2 adsorption capacities are slightly lower in three adsorption/desorption cycles.

Synthesis, IR spectroscopic and structural studies of erbium and nickel complexes with N,N'-tetraethyl-N''-trifluoroacetylphosphoroustriamide

A synthesis procedure was developed and a new carbacylamidophosphate type ligand N,N'-tetraethyl-N''-trifluoroacetylphosphoroustriamide (CF3C(O)NHP(O)(NC2H5)2, HL) that contains C(O)NP(O) chelating fragment was isolated in the crystalline state. A mononuclear erbium complex [Er(HL)3(NO3)3] and a tetranuclear nickel complex [Ni4L4(OCH3)4(CH3OH)4] were isolated in the crystalline state. The suggestion about the type and coordination mode of the ligand in complexes was made based on IR spectroscopic investigations: deprotonated (acido-) form in bidentate manner in nickel complex and neutral form in monodentate manner in erbium complex. According to X-ray structural studies, different coordination modes of the ligand in complexes were determined: bidentate chelate manner via the oxygen atoms of the phosphoryl and carbonyl groups of the ligand with the formation of six-membered chelate cycles in case of nickel complex and monodentate manner via the oxygen atom of the phosphoryl group of the ligand in case of erbium complex, the coordination polyhedron of which was interpreted as a distorted three-handed trigonal prism.

Evaluation of effect of synthesis parameters on the morphology of nano-structures of magnesium oxide coated with carbon

In this study, the influence of the synthesis parameters on the microstructural properties of nanoparticles of magnesium oxide coated with carbon was investigated. The nanostructures were produced in a one-step synthesis procedure, following a sol-gel method, and the effects of the molar ratio between magnesium nitrate and glucose, the temperature and the dripping time on the morphology of the nanostructures formed were analyzed. The results indicate that an increase in carbon concentration, synthesis temperature around 60 °C and 4 h of dripping time favor the formation of small agglomerates of nanoparticles with greater carbon coating homogeneity. In general, high synthesis temperatures favor the kinetic aspects of crystallization and produce nanostructures with a larger crystallite size. On the other hand, altering the dripping time was not efficient in changing the morphology of the nanostructures obtained. In addition, increasing the carbon concentration favors the formation of structures with small surface area and pore volume.